Crystalline Silicon Research Articles

Monitoring solar irradiance and PV module performance in mobile applications

The paper presents a comprehensive evaluation of a PV module attached to an electric vehicle using a custom developed PV monitoring system to estimate the effect of PV energy production on the driving range.A rigid crystalline silicon photovoltaic (PV) module with a nominal peak power of 192.4 W accompanied with four irradiance sensors (positioned horizontally and vertically to the left, right and back) was mounted on an electric car, and various driving scenarios were executed, with data recorded for analysis. The results of a two-month continuous monitoring of the car's usage mainly in the Central Slovenia region in late winter and early springtime, show that the daily energy generation by the installed PV module contributed an additional driving range of up to 5 km per day, totalling 93 km of additional range in the entire monitoring period. Based on irradiance monitoring results applied to a hypothetical case where all sides would be covered with a state-of-the-art PV, the driving range would extent to 471 km in total for the same period. When compared to a fixed, ideally installed PV module at our outdoor PV monitoring site in Ljubljana, the average performance ratio (PR) of the mobile PV module in the two-month period was 87 %, whereas the PR of the fixed installed PV module was 83 %. The energy yield varied significantly under the varying conditions resulting from different car usage scenarios and on average it reached 41 % of the fixed PV module's energy yield. Through real-world experiments and data collection, different car use cases under various driving and parking conditions are presented and evaluated in detail. From these, the base specifications of a dedicated mobile VIPV monitoring system are identified.

Towards end-of-life of photovoltaic systems in Malaysia: An assessment of management strategies using a life cycle approach

This paper presents the development of photovoltaic (PV) end-of-life (EoL) policy options in Malaysia with consideration of the respective environmental impacts and economic implication. Five policy options were initially formulated based on different combinations of voluntary and regulatory approaches, PV module EoL pathways, i.e. recycling, landfill and incineration, and types of EoL PV modules. Then, the environmental impacts of each option were evaluated using life cycle assessment based on seven relevant impact categories. Later, the economic implication of each policy option was determined based on revenue gained from recovered materials and cost of recycling. Results showed that recycling yields net environmental benefits in all impact categories for crystalline silicon (c-Si) modules and almost all impact categories for cadmium telluride (CdTe) modules. While both regulatory and voluntary approaches offer reduced environmental impacts, the former is more beneficial than the latter as it provides higher quantity of recycled EoL PV modules, net environmental benefit, net primary energy avoidance and net economic benefit. Also, the inclusion of both c-Si and CdTe in recycling is preferred as it yields higher quantity of recycled PV modules as well as higher net environmental benefit and net primary energy avoidance gained in most impact categories. However, the net economic benefit is lower than recycling c-Si alone because the cost of recycling CdTe modules is higher than the revenue gained from recovered materials. These findings seek to assist in establishing sustainable EoL PV management.

Improvements in Long-Term Durability of CO2 Electrolyzer Producing Formate Designed for Integration with Solar Cells for Artificial Photosynthesis

Artificial photosynthetic cells have been extensively studied for carbon neutrality, yet in lab-scale. We have previously constructed practically large-sized cells consisting of CO2 electrolyzers and crystalline silicon solar cells.1,2 Our CO2 electrolyzers adopt a facing cathode-anode configuration, using a Ru complex polymer (RuCP) catalyst realizing a low overpotential for CO2 reduction and an IrO x -based catalyst with a high catalytic activity for water oxidation.3 1000 cm2-sized cells achieved a solar-to-chemical energy-conversion efficiency (η STC) of 7.2%,1 and a further scaled-up 1 m2-cell demonstrated a higher η STC of 10.5%, yielding a large formate production rate of 1.2 mol/h.2 In the present study, we improved the long-term durability of the CO2 electrolyzer. We prepared the 75 cm2-sized CO2 electrolyzer using the improved cathode and the anode, and achieved high formate Faradaic efficiencies (FE) exceeding 80% and electricity-to-chemical energy-conversion efficiencies (η ETC) of around 60% even after 3000 h operation under practical conditions, as shown in Fig. 1.In the previous large-sized cells, the operating current gradually decreased during continuous operation within dozen of hours. We investigated the causes of the degradation and identified three key factors. Two of these factors were associated with the cathode electrodes: detachment of the RuCP catalyst from the carbon supports and peeling off of the carbon supports from the conducting Ti substrates. An introduction of a pyrrole derivative containing amino group in the RuCP, coupled with an application of a UV-ozone treatment to create carboxyl groups on the carbon supports, effectively reduced the detachment of the RuCP catalyst by forming strong chemical bonds. A newly-developed chemically-resistant graphite adhesive composed of graphite particles and a polyvinylidene fluoride (PVDF) binder prevented the carbon supports from peeling off from the Ti-plates. The post-loading process of the RuCP, i.e., RuCP-loading on the carbon supports already-bonded on the Ti-plates using the new adhesive eliminated the detrimental impact of the heat treatment for curing the adhesive. The third factor involved detachment of the anode catalyst of IrO x particles from the Ti-plates.4 Therefore, we replaced the IrO x anodes with highly durable counterparts comprising IrO x -TaO x /Pt-Metal oxide/Ti-plates.Another critical issue we addressed was the validity of laboratory-based evaluations for reflecting outdoor operations. In our previous study, we vertically installed the integrated CO2 electrolyzers and solar cells on the ground and evaluated their performance under continuous simulated sunlight (ca. 1 sun).2,3 This vertical setup was chosen to prevent a decrease in η STC caused by crossover reactions that would occur when the electrolyzers are inclined. Indeed, it has been reported that oxygen reduction reaction (ORR) of the O2 bubbles generated at the anode and transferred to the cathode can be substantial in a single-chamber water-splitting reactor.5 By contrast, although the present CO2 electrolyzer was installed at an inclined angle of 30 °, which is approximately the optimal value for receiving more solar energy, the crossover reactions were well-suppressed because the porous separator film inserted between the facing cathode and anode impeded the transfer of O2 bubbles from the anode to the cathode. However, the use of a separator film raised another issue: the O2 bubbles trapped on the film narrowed the effective film area. Intermittent operation corresponding to changes in solar energy during the day mitigates the detrimental impact of the second issue.Thus, we established the groundwork for the widespread use of integrated CO2 electrolyzers and solar cells for artificial photosynthesis, demonstrating high durability, exceptional FE, and η ETC.References N. Kato, et al., A large-Sized Cell for Solar-Driven CO2 Conversion with a Solar-to-Formate Conversion Efficiency of 7.2%, Joule, (2021) 5, 687.N. Kato, et al., Solar Fuel Production from CO2 using 1 m-square-sized Reactor with a Solar-to-Formate Conversion Efficiency of 10.5%, ACS Sustain. Chem. Eng.,(2021) 9, 16031.T. Arai, S. Sato, T. Morikawa, A Monolithic Device for CO2 Photoreduction to Generate Liquid Organic Substances in a Single-Compartment Reactor, Energy Environ. Sci., (2015) 8, 1998.M. Shiozawa, et al., Improved Durability of Highly Active IrO x Electrodes for Electrocatalytic Oxygen Evolution Reaction, Electrocatalysis, (2022) 13, 830.K. Obata, et al., Multiphase Fluid Dynamics Simulations of Product Crossover in Solar-driven, Membrane-less Water Splitting, Cell Rep. Phys. Sci, (2021) 2, 100358. Figure 1

Electrochemical Recovery of Cd and Te from CdTe Solar Panels

CdTe photovoltaic (PV) solar panel occupies approximately 5% of the PV solar panel market worldwide, as the second deployed PV technology following crystalline silicon. To ensure a circular economy of critical materials, it is important to recover Cd and Te from end-of-life CdTe solar cells. Current industrial recycling processes of CdTe solar panels involve multiple stages of chemical oxidation, separation, and precipitation, which require high energy and chemical consumption. Different electrochemical processes are compared and evaluated to recover Cd and Te from shredded CdTe solar cells as possible alternatives. Cd and Te are selectively leached and precipitated with mediated electrochemical oxidation processes. In this ongoing work, electrochemical systems show potential to decarbonize the CdTe recycling industry.

A Study on the Kinetics and Structural Changes of Silicon during Ball Milling

Enhancing our understanding of the ball milling process is important to optimize silicon amorphization, a key factor in improving the performance of lithium-ion battery anodes. To improve this understanding, we quantitatively studied the kinetics of silicon amorphization during ball milling using x-ray diffraction (XRD) and electrochemical methods, among other methods. The percentage of amorphous and crystalline silicon was deduced by fitting the XRD data and electrochemical results. The resulting trend versus ball milling time was then fitted using the Avrami model. The material resulting from ball milling was further studied using scanning and transmission electron microscopy (SEM/TEM). Under extended milling times, we found that a maximum of 86% of the silicon became amorphous. Similarly, the grain size of the crystalline silicon phase could not be reduced below 6 nm. Our observations suggest that amorphization results from defects creation during ball milling. Amorphization then stops when the grain size reaches a limit where defects are no longer formed. Figure 1

P-Doped Carbon Nanotubes As Light Absorbers and Electron Donors in Photovoltaics

Doping is a ubiquitous and powerful tool used to alter a material’s electronic properties. Conventional Si solar cells would not exist without it, and it has been used to increase the efficiency of organic and inorganic photovoltaics alike. While doped carbon nanotubes (CNTs) have been the subject of numerous spectroscopic studies, few investigations have examined their performance in photovoltaic devices. Here, we incorporate chemically p-doped CNTs into photovoltaic heterojunctions with C60. In a conventional CNT–C60 heterojunction device, photocurrent can be produced when photogenerated excitons in the CNT layer diffuse to the CNT–C60 heterointerface. The offset in conduction band energy drives dissociation of these excitons via photoelectron transfer from CNT to C60, which yields separated charges that can be collected. Our objective here was to determine the following: 1) does p-doping increase or decrease the efficiency with which excitons dissociate into electrons and holes? 2) Do p-dopants trap excitons and inhibit their diffusion to the heterointerface? 3) How efficiently can a photogenerated trion (exciton coupled to an injected hole) be dissociated to produce a photocurrent?To answer these questions, we fabricated polymer wrapped (6,5) CNT–C60 heterojunctions over a range of CNT thickness with various levels of p-doping introduced by triethyloxonium hexachloroantimonate treatment. We measured photocurrent to quantify relative photoelectron transfer efficiency for both excitons and trions and compared this to photoluminescence and transient absorbance measurements on doped CNT films. We found that p-doping decreases photocurrent because injected holes bleach the CNTs’ S11 transition and decrease the amount of light absorbed. Meanwhile, the photogenerated exciton to collected electron transfer efficiency remains unchanged for doping densities up to 50μm-1. In contrast, photoluminescence quantum yield drops by over 90% at an equivalent doping density. We attribute this disparity to the fast electron transfer at the CNT–C60 interface, which occurs on the order of femtoseconds. We also found that moderate doping can promote photocurrent at the trion peak, with a photogenerated trion to collected electron transfer efficiency about 1/4 that of the photogenerated exciton to collected electron transfer efficiency. Photocurrent at the trion absorption peak is invariant with reverse bias up to 0.3 V, despite the charged nature of the trion, supporting evidence for the immobile nature of trions. These results indicate that p-CNTs are a viable material for use in photovoltaics, albeit with weaker absorption, and that photocurrent from trions is possible, although with lower quantum efficiency. Figure 1

Enhancing Methylated Amorphous Silicon Anode Performances in Li-Ion Batteries By Boron Doping

Methylated amorphous silicon has already demonstrated some advantages as compared to silicon in terms of mechanical properties and cyclability for Li-ion batteries (LIB) [1]. However, the conductivity of methylated amorphous silicon drops by several orders of magnitude when increasing the methyl content in the material, which prevents investigating methyl contents higher than 10%. It is well known that doping significantly improves the conductivity of crystalline or amorphous silicon, and has sometimes been reported to improve the material cyclability when used as a LiB anode [2].Here, boron-doped methylated amorphous silicon electrodes with different methyl contents were investigated as anodes for LiB in half-cell configuration. Boron doped methylated silicon thin films (100nm thick) with various methyl content were cycled in the range 0.025V – 1V at C/2 rate (electrolyte: LP30 with 5%FEC). 10% methylated amorphous silicon with 2% boron doping performs a capacity retention of 77% after 1000 cycles (exhibiting a capacity around 1800 mAh.g-1) of full lithiation/delithiation. Figure 1a shows a clearly improved performance as compared to the undoped material. The stability upon cycling of higher methyl contents (15% and 20%) electrodes is further increased, with a capacity retention exceeding 80% over 1000 cycles of full lithiation/delithiation.The evolution of the SEI thickness can be quantitatively determined from IR spectra during cycling. The thickness in the delithiated state is found to increase from cycle to cycle, but with a lower rate for the doped 10% methylated electrodes (thickness lower than 25 nm after 40 cycles and 30 nm after 80 cycles) than for the undoped ones (thickness larger than 35 nm after 40 cycles), see Figure 1b. The SEI evolution upon cycling for higher methyl content is currently under investigation. Reference [1] L. Touahir, A. Cheriet, D. A. D. Corte, J.-N. Chazalviel, C. H. Villeneuve, F. Ozanam, I. Solomon, A. Keffous, N. Gabouze et M. Rosso, «Methylated silicon: A longer cycle-life material for Li-ion batteries,» Journal of Power Sources, vol. 240, pp. 551-557, 10 2013. [2] M. Salah, C. Hall, P. Murphy, C. Francis, R. Kerr, B. Stoehr, S. Rudd et M. Fabretto, «Doped and reactive silicon thin film anodes for lithium ion batteries: A review,» Journal of Power Sources, vol. 506, p. 230194, 9 2021. Figure 1

Large-Scale Artificial-Photosynthetic Production of Formate and Isolation of Pure Formic Acid

We proposed a concept of an artificial-photosynthetic system to produce pure formic acid using CO2, water, and solar energy, generating no waste, as illustrated in Fig. 1.1 The system consists of an artificial-photosynthetic reaction process and a product isolation process. We proved the concept by small-scale experiments, and constructed a practically large-sized solar-driven CO2 electrolyzer as the first step toward widespread use of artificial photosynthesis.2,3 We adopted a single-compartment configuration of the solar-driven CO2 electrolyzer without ion-exchange membranes and a near-neutral pH electrolyte of a potassium phosphate buffer aqueous solution to simplify the reactor structure. The large-sized electrolyzer was composed of eight-stacked cathode-anode-electrode pairs of 1 m×1 m in size and powered by crystalline silicon solar cells installed on the electrolyzer housing via a DC-DC converter. The raw material of 100% CO2 gas was dissolved in the electrolyte and supplied to the cathode-electrode surfaces uniformly with the help of well-designed flow channels. The electrochemically synthesized formic acid was dissolved in the electrolyte and ejected from the electrolyzer. Insertion of nanoporous separator between the facing anode/cathode electrodes prevented O2 bubbles produced on the anodes from reaching the cathodes, suppressing the crossover reaction of O2 reduction. We developed a novel Ru complex polymer (RuCP)-based cathode catalyst loaded on carbon supports and an IrO x -based anode catalyst, and achieved a Faradaic efficiency as high as 96% for the formic acid synthesis at an extremely low operating voltage of 1.65 V (overpotential of only 0.22 V) and a large current of 65 A, resulting in a high solar-to-chemical energy conversion efficiency of 10.5%. This significant performance was realized by the low-resistive Ti substrates of the cathode and anode electrodes, sufficient CO2 supply to whole of the cathode surfaces, etc., which have greater impacts on a larger electrolyzer, in addition to the high catalytic activity of the RuCP and IrO x . Further, we tackled to improve both activity and durability of the anode and cathode electrodes,4,5 and to realize direct reduction of CO2 in a flue gas to eliminate energy-consuming CO2 capture processes.6 Moreover, we designed tandem solar modules suitable for direct coupling with the electrolyzers using organic-inorganic hybrid perovskite solar cells.7 The next challenge was isolation of the synthesized formic acid dissolved in the aqueous electrolyte. The formic acid cannot be isolated by distillation because its boiling point (101 °C) is virtually the same as that of water. Thus, we developed an isolation process on the basis of reactive extraction, including three sequential steps.1 The first step was reactive extraction of the formic acid from the electrolyte using an extraction solution composed of an organic base (tri-n-octylamine, TOA, boiling point 366 °C) as an extractant and an organic solvent (dichloromethane, DCM, boiling point 40 °C) as a diluent. Although formic acid is highly miscible in water, it was extracted into DCM because the formic acid formed a complex salt with TOA that is insoluble in water. The second step was removal of DCM from the mixture of the extracted formic acid, TOA, and DCM produced in the first step, by evaporation at 40 °C at 0.03 MPa. Finally, the residue was heated at 160 °C at 0.02 MPa for isolation of the formic acid by distillation in the third step. The large differences in the boiling points among these three chemicals secured few contaminations in the second and third steps. In addition, the composition of the electrolyte was tuned for promotion of the formation of the formic acid-TOA complex salt. Thus, we achieved an over 90% isolation yield of pure formic acid. The new electrolyte was confirmed to lower the energy conversion efficiency by only 10%(relative) and to secure similarly high durability compared with the original electrolyte. The great feature of the isolation process is that all the electrolyte, TOA, and DCM are reused for the next synthesis and isolation after the formic acid is isolated. Thus, we established a highly sustainable artificial-photosynthetic system that consumes no chemicals other than the raw materials of CO2 and water, or generates no waste.References M. Shiozawa,et al., Energy & Fuels, submitted.N. Kato, et al., Joule, (2021) 5, 687.N. Kato, et al., ACS Sustain. Chem. Eng.,(2021) 9, 16031.M. Shiozawa, et al., Electrocatalysis, (2022)13, 830.N. Kato, et al., submitted to 245th ECS Meeting , Symposium I04: Electrosynthesis of Fuels 8 (2024).Y. Takeda, et al., J. CO2 Util., (2023)71, 102472.Y. Takeda, et al., J. Appl. Phys., (2022)132, 075002. Figure 1

Study on Electrochemical Characteristics of Crystal Structure Changes Effects of Silicon Anode Materials for Lithium Ion Batteries

Graphite is widely used as a representative anode material in commercialized lithium-ion secondary batteries. However, with a theoretical capacity of 370 mAh/g, it is difficult to manufacture high-capacity/high-density lithium-ion secondary batteries. Therefore, research is actively underway to find high-capacity substances to replace graphite. Silicon anode materials are currently attracting attention as next-generation high-capacity cathode materials. Silicon forms Li4.4Si when fully charged through an alloying/dealloying process with lithium during the reaction. Graphite is intercalation/deintercalation in reaction with lithium and LiC6 is formed when fully charged. That's why silicon has a theoretical capacity of 3800 mAh/g, about 10 times that of graphite.However, silicon is a high-capacity electrode material that overcomes the theoretical capacity limit of graphite, and has the disadvantage of experiencing volume expansion of about 400% during repeated charge/discharge cycles. Problems such as material cracks due to volume expansion can affect the safety of the battery. Various studies are being conducted to solve silicon-related challenges to effectively utilize silicon materials. Previous studies have explored the use of binders or additives to mitigate volume expansion. In addition, various types of silicon materials such as Si alloy and SiOx are being developed to suppress volume expansion through matrix formation. Nevertheless, despite the development of silicon materials, structural changes in the charging and discharging process of silicon remain unclear.This study aims to analyze the structural changes that occur during the charging and discharging process of silicon. The experiment evaluates the electrochemical characteristics of crystalline silicon and amorphous silicon and compares the behavior and structural changes during charging/discharging. The volumetric expansion measurements are performed with electrochemical characterization, and ex-situ X-ray diffraction (XRD) and transmission electron microscope (TEM) analyses are performed for comparison with crystal structural changes.

Surface Modification of Cellulose Films By Dielectric Barrier Discharge for Organic Photovoltaics Encapsulation

Organic photovoltaics (OPV) are the third generation of solar cells and are more and more attractive for industrial applications. OPV present numerous advantages, such as flexibility, low cost, light weight, large-area production.[1,2] Nonetheless, OPV are not as efficient as the conventional crystalline silicon photovoltaic (PV) cells. Recently, power conversion efficiency (PCE) has reached 18% for OPV, while conventional PV remains around 30% [3]. In this sense, additional works are necessary to improve their processability. Moreover, components of OPV are highly sensitive to water or oxygen, which strongly affect OPV stability in time when used in harsh conditions. Therefore, development of new barrier coatings are today essential to reduce OPV degradation and increase their shelf life. According to the literature, encapsulation can be performed following three strategies: (i) glass-glass encapsulation, (ii) flexible polymer lamination and (iii) thin film direct deposition. Glass-glass encapsulation provides great protection, with good optical properties but it remains fragile and is not compatible with roll-to-roll processes. On the other hand, although, flexible polymer lamination is suitable for roll-to-roll processes, adhesion between the front and back barriers is still complex to deal with, leading sometimes to partial encapsulation, thus increasing OPV degradation. Finally, direct deposition allows to obtain thin films with excellent optical and oxygen and humidity barrier properties. To date, most of thin layers are synthesized under vacuum [1,2]. This work focus on the development new barrier coatings at atmospheric pressure, compatible with roll-to-roll processes using cellulose nanofibrils with excellent oxygen barrier properties [4]. Being hydrophilic, the surface of cellulose nanofibrils have been modified to improve the water barrier properties. Wettability modification (WCA ~ 140°) was successfully achieved with an atmospheric pressure dielectric barrier discharge to control the fragmentation/reticulation of 2,4,6,8-Tetramethylcyclotetrasiloxane (TMCTS).

Elucidating the Effect of Pre-Lithiation of Silicon Dominant Anodes on the Full Cell Performance

Over the last few years, there has been a high interest in increasing the energy density of lithium-ion batteries in order to increase the driving range of battery electric vehicles. On a material level, silicon is a promising anode active material candidate due to its high theoretical capacity of 3579 mAh g-1, which is approximately ten-fold higher than that of the currently used graphite anodes with a theoretical capacity of 372 mAh g-1.[1] However, the main drawbacks of silicon are its intrinsic volume expansion of +300 % upon lithiation.[2] This leads to rupturing of the passivating solid electrolyte interphase (SEI), particle cracking, and loss of electronic contact, limiting the lifetime of batteries with silicon based anodes, thus hindering their transition into application.As a possible solution, Jantke et al. proposed the concept of partial utilization of µm-sized crystalline silicon, where only one-third of the theoretical capacity is used for (de)lithiation. Thereby, a crystalline core remains, and the volume expansion on the particle-level is reduced to approximately + 100%.[3] In addition, it was shown that irreversible losses during the formation and upon cycling can be compensated by pre-lithiation of the anode, which increases the lifetime significantly.[4,5] In this study, we investigated a promising cell chemistry for high-energy applications, containing a Si-dominant anode and a cathode based on a Co-free lithium- and manganese-rich NMC. The here used anode consists of 70 wt% silicon, 20 wt% graphite, 2 wt% conductive C65, and 8 wt% LiPAA-binder. Note that graphite mainly acts as a conductive additive within the operating voltage window, with a negligible contribution to the overall anode capacity. The electrochemical testing was conducted at 25 °C in Swagelok® T-cells containing two glass fiber separators, a 1M LiPF6 in FEC:DEC (2:8, v:v) electrolyte and a lithium metal reference.Without pre-lithiation, these full-cells suffered from rapid capacity fading, reaching the 80 % state-of-health (SOH) criterion after ~100 cycles. As will be discussed, our analysis shows that the primary mode of failure in these cells is the loss of cyclable lithium, evidenced by an increase in the end-of-discharge potential at the anode. It was found that with increasing end-of-discharge potential at the anode, the anode resistance at low state-of-charge rises significantly.Therefore, silicon anodes were lithiated in coin half-cells to 25, 50, and 75 % of the reversible cathode capacity (corresponding to 300, 600, and 900 mAh gSi -1). Then, the anodes were harvested in the lithiated state and assembled in a Swagelok® T-cell with the same cathode, separator, and electrolyte as the non-pre-lithiated reference cells. Pre-lithiation leads to similar reversible charge/discharge capacities, but generates a cyclable lithium reservoir in the anode.Successively increasing the pre-lithiation of the anode increases the lifetime from 100 to 550 cycles. The onset of the above-described aging phenomena is delayed by 150 cycles for every additional 25 % pre-lithiation. Further, the influence of aging and lithium inventory on anode and cathode resistance will be discussed, showing that the increase in anode resistance is mainly a function of (de)lithiation rather than cycle number.Acknowledgments:The authors gratefully acknowledge the funding from the BMBF (Federal Ministry of Education and Research, Germany) in the ExZellTUM III project (grant number 03XP0255). We also kindly thank Wacker Chemie AG and BASF SE for providing the anode and cathode active materials.

(Invited) Mie Resonant Silicon Nanosphere Nanoantenna for Fluorescence Enhancement

A nanoantenna is a device that manipulates light propagation and enhances light-matter interaction at the nanoscale. Integration of an emitter into a nanoantenna capable of increasing local density of photonic states at the emission wavelength results in the enhancement of the spontaneous emission rate (Purcell effect) and modifies the emission spectrum. A nanoantenna can also control the directionality and radiation pattern of an emitter. Traditionally, plasmonic nanoantennas made from gold or silver nanostructures supporting localized surface plasmon resonances had been the main stream of the nanoantenna research. Recently, high refractive index nanoparticles having low-order Mie resonances have been attracting attention as a new type of dielectric nanoantennas. Advantages of a dielectric nanoantenna compared to a plasmonic one are the smaller loss and the possession of magnetic type Mie resonances arising from light-induced displacement current. By properly controlling the overlap of the magnetic and electric multipole resonances, radiation patters of an emitter placed nearby can be tailored with high degree of freedom. Furthermore, magnetic-type Mie resonances can couple with higher-order optical transitions of an emitter such as a magnetic-dipole transition, and thus can enhance and control radiation from otherwise weak forbidden transitions.Recently, we have succeeded in producing perfectly spherical nanoparticles of crystalline silicon (Si) in 100-300 nm in diameters. These Si nanospheres exhibit the electric and magnetic multipole resonances at the optical frequency [1]. In this presentation, we first show scattering and absorption properties of the Mie resonant Si nanospheres. Especially, we show that solutions of size-purified Si nanospheres exhibit vivid structural color and the solutions can be used as structural color inks. We then show that the solutions can preserve helicity of incoming circularly-polarized light and can enhance local chiral fields around nanospheres [2, 3]. This property can be used to improve the sensitivity of enantiomer-selective chiral molecular sensing. We then show some examples of enhanced light-matter interaction by Si nanoparticles. These include enhancement of magnetic dipole transitions of an emitter by magnetic-type Mie resonances of Si nanospheres (magnetic Purcell effect) [4, 5], enhancement of excitation and emission processes of in-plane dipoles of monolayer transition metal dichalcogenides (TMDC) [6], and enhancement of a spin forbidden singlet-to-triplet absorption transition of a molecule by Si nanodisks [7, 8].

All-back-contact neutral-colored transparent crystalline silicon solar cells enabling seamless modularization

Transparent solar cells (TSCs) hold substantial potential as continuous energy generators, enabling their use in situations where conventional devices may not be feasible. However, research aimed at modularizing TSCs for the purpose of regulating the overall voltage and current they produce, a critical step toward practical application, is still in its nascent stages. In this study, we explored a custom-designed, all-back-contact (ABC) configuration, which situates all electrical contacts on the rear side, to create glass-like transparent crystalline silicon (c-Si) solar cells and seamless modules. The ABC design not only demonstrates high power conversion efficiency (PCE) in solar cells but also ensures unobstructed visibility through transparent solar modules. Notably, ABC-transparent c-Si solar cells achieved a peak PCE of 15.8% while maintaining an average visible transmittance of 20%. Through seamlessly interconnecting the unit cells, the output voltage and power were systematically tuned from 0.64 V and 15.8 mW (for a 1 cm2-sized unit cell) to 10.0 V and 235 mW (for a 16 cm2-sized module). Furthermore, we successfully demonstrated the photocharging of a smartphone using a transparent ABC solar module.

Formation and annihilation of bulk recombination-active defects induced by muon irradiation of crystalline silicon

Muons are part of natural cosmic radiation but can also be generated at spallation sources for material science and particle physics applications. Recently, pulsed muons have been used to characterize the density of free charge carriers in semiconductors and their recombination lifetime. Muon beam irradiation can also result in the formation of dilute levels of crystal defects in silicon. These crystal defects are only detected in high carrier lifetime silicon samples that are highly sensitive to defects due to their long recombination lifetimes. This work investigates the characteristics of these defects in terms of their formation, recombination activity, and deactivation. Charge carrier lifetime assessments and photoluminescence imaging have great sensitivity to measure the generated defects in high-quality silicon samples exposed to ∼4 MeV (anti)muons and their recombination activity despite the extremely low concentration. The defects reduce the effective charge carrier lifetime of both p- and n-type silicon and appear to be more detrimental to n-type silicon. Defects are created by transmission of muons through the wafer, and there are indications that slowed or implanted muons may create additional defects. In a post-exposure isochronal annealing study, we observe that annealing at temperatures of up to 450 °C does not by itself fully deactivate the defects. A recovery of charge carrier lifetime was observed when the annealing was combined with Al2O3 surface passivation, probably due to passivation of bulk defects from hydrogen from the dielectric film.

Systematic Modeling and Optimization for High‐Efficiency Interdigitated Back‐Contact Crystalline Silicon Solar Cells

This study utilizes Quokka3, an advanced solar cell simulation program, specifically tailored for interdigitated back‐contact (IBC) crystalline silicon (c‐Si) solar cells. Through meticulous Quokka3 simulations, the influence of several geometric and wafer characteristics of the solar cell backside on current–voltage (I–V) performance has been scientifically explored for IBC c‐Si solar cells. The investigation encompasses parameters such as wafer thickness, bulk lifetime, resistivity, emitter and back surface field area fraction, and front‐ and rear‐surface passivation. Optimal values for these parameters have been proposed to enhance the efficiency of IBC solar cells. These recommendations contain an emitter percentage of 70%, a wafer thickness ranging from 200 μm, a wafer resistivity of 1 Ω cm, and a wafer bulk lifetime of at least 10 ms. Moreover, under conditions where the cell is not short‐circuited, the potential for achieving higher cell efficiency, up to 26.64%, has been shown.

Predicting buckling regimes during first lithiation of a crystalline silicon cylindrical anode particle: Influence of size and charging rate

A mathematical model for buckling analysis during the first lithiation of cylindrical crystalline silicon (c-Si) anode particles is presented using the finite deformation framework. A reaction–diffusion model that incorporates a reversible alloying–dealloying reaction (ADR) captures the lithiation in the expanding amorphous zone, while an addition reaction models the dynamics of the crystalline-amorphous silicon interface. A “movable” lithium part and an “immovable” lithium part make up the full lithium. In sharp contrast to the case of amorphous silicon (a-Si), the axial force evolution in c-Si is found to show two different peaks during the initial and final stages of lithiation, respectively. These peaks form the basis of two different buckling criteria, which, in turn, are shown to be sensitively influenced by the influx of lithium and a crucial size-dependent parameter. This framework gives an insight towards investigating the buckling phenomena for lithiation with an evolving amorphous silicon zone due to the interface movement, which is still absent in the present literature. Additionally, the present model enables us to obtain a quantitative and mechanistic insight into and capture the previous experimental observation that the mechanical stability of a cylindrical silicon particle may be improved by maintaining a crystalline silicon core inside the amorphous shell through controlled first lithiation. It is shown that such a crystalline-amorphous core–shell structure can be advantageous to more complicated designs involving carbon fiber as the core. It is thus hoped that this model will contribute towards improving the theoretical underpinnings of an improved design of mechanically robust electrodes for next-generation batteries.

A novel approach of polychiral single walled carbon nanotubes functionalization for heterojunction solar cell

This study introduces an innovative method for functionalizing polychiral single-walled carbon nanotubes (f-SWCNTs) by depositing thin films onto n-type crystalline silicon (n-Si), thereby creating efficient heterojunction solar cells. The approach capitalizes on the effective charge separation facilitated by the built-in potential resulting from the functionalization of polychiral SWCNTs, leading to enhanced electron transfer from f-SWCNTs to Si driven by functional groups. The resulting f-SWCNT/Si heterojunction device demonstrates remarkable performance, attributed to the high optical absorption and improved charge separation and transfer mechanisms of the f-SWCNT film. Moreover, by adjusting the concentration of f-SWCNTs, the film properties and overall device performance have been customized, achieving a notable power conversion efficiency of 12 %. These discoveries serve as a foundation for the advancement of highly desirable, efficient, cost-effective, and broadband high-performance f-SWCNT/Si heterojunction solar cells

The Effect of Quantum Dots on the Performance of the Solar Cell

Quantum dot solar cells are currently the subject of research in the fields of renewable energy, photovoltaics and optoelectronics, due to their advantages which enables them to overcome the limitations of traditional solar cells. The inability of ordinary solar cells to generate charge carriers, which is prevents them from contributing to generate the current in solar cells. This work focuses on modeling and simulating of Quantum Dot Solar Cells based on InAs/GaAs as well as regular type of GaAs p-i-n solar cells and to study the effect of increasing quantum dots layers at the performance of the solar cell. The low energy of the fell photons considers as one of the most difficult problems that must deal with. According to simulation data, the power conversion efficiency increases from (12.515% to 30.94%), current density rises from 16.4047 mA/cm2 for standard solar cell to 39.4775 mA/cm2) using quantum dot techniques (20-layers) compared to traditional type of GaAs solar cell. Additionally, low energy photons' absorption range edge expanded from (400 to 900 nm) for quantum technique. The results have been modeled and simulated using (SILVACO Software), which proved the power conversion efficiency of InAs/GaAs quantum dot solar cells is significantly higher than traditional (p-i-n) type about (247%)

Impedance dynamics in tandem solar cells based on c-Si with upper layers of CsPbBr3 (CsPbI3) perovskite nanocrystals

The application of an additional nanoparticle layer is a common practice for enhancing the optical and electrical properties of third-generation solar cells. In this study, we present the results of impedance spectroscopy (IS) for modified solar cells using Nyquist and Bode diagrams. The structure investigated consists of a conventional double junction based on crystalline silicon (c-Si) coated with thin films of inorganic perovskite nanocrystals (NC) of lead halides CsPbI3 and CsPbBr3. The latter are characterized by a significant phonon disorder, which leads to unique electron-phonon interactions and dielectric responses. The IS results indicate that, under the same conditions, the measured Nyquist plots align well with the simulated ones. An equivalent circuit model is proposed, featuring ohmic resistance, recombination resistance, and geometric capacitance. These elements arise due to charge accumulation, charge transfer resistance, and/or additional interfacial electronic states. The study finds that the introduction of a CsPbI3 layer enhances the photoresponse under bias conditions, but this photoresponse leads to a decrease in DC conductivity. In contrast, the addition of a CsPbBr3 layer obstructs the photoresponse under bias while slightly improving the photoresponse in the absence of an applied voltage. The results obtained contribute to the improvement of tandem solar cell characteristics featuring top layers of perovskite nanocrystals.

Optimizing Geometry and ETL Materials for High-Performance Inverted Perovskite Solar Cells by TCAD Simulation.

Due to the optical properties of the electron transport layer (ETL) and hole transport layer (HTL), inverted perovskite solar cells can perform better than traditional perovskite solar cells. It is essential to compare both types to understand their efficiencies. In this article, we studied inverted perovskite solar cells with NiOx/CH3NH3Pb3/ETL (ETL = MoO3, TiO2, ZnO) structures. Our results showed that the optimal thickness of NiOx is 80 nm for all structures. The optimal perovskite thickness is 600 nm for solar cells with ZnO and MoO3, and 800 nm for those with TiO2. For the ETLs, the best thicknesses are 100 nm for ZnO, 80 nm for MoO3, and 60 nm for TiO2. We found that the efficiencies of inverted perovskite solar cells with ZnO, MoO3, and TiO2 as ETLs, and with optimal layer thicknesses, are 30.16%, 18.69%, and 35.21%, respectively. These efficiencies are 1.5%, 5.7%, and 1.5% higher than those of traditional perovskite solar cells. Our study highlights the potential of optimizing layer thicknesses in inverted perovskite solar cells to achieve higher efficiencies than traditional structures.