Power Conversion Efficiency Of Device Research Articles

Tuning the morphology and energy levels in organic solar cells with metal–organic framework nanosheets

Metal–organic framework nanosheets (MONs) have proved themselves to be useful additives for enhancing the performance of a variety of thin film solar cell devices. However, to date only isolated examples have been reported. In this work we take advantage of the modular structure of MONs in order to resolve the effect of their different structural and optoelectronic features on the performance of organic photovoltaic (OPV) devices. Three different MONs were synthesized using different combinations of two porphyrin-based ligands meso-tetracarboxyphenyl porphyrin (TCPP) or tetrapyridyl-porphyrin (TPyP) with either zinc and/or copper ions and the effect of their addition to polythiophene-fullerene (P3HT-PC71BM) OPV devices was investigated. The power conversion efficiency (PCE) of devices was found to approximately double with the addition of MONs of Zn2(ZnTCPP) -4.7% PCE, 10.45 mA/cm2 short-circuit current density (JSC), 0.69 open-circuit voltage (VOC), 64.20% fill-factor (FF), but was unchanged with the addition of Cu2(ZnTPyP) (2.6% PCE, 3.68 mA/cm2JSC, 0.59 VOC, 46.27% FF) and halved upon the addition of Cu2(CuTCPP) (1.24% PCE, 6.72 mA/cm2JSC, 0.59 VOC, 56.24% FF) compared to devices without nanosheets (2.6% PCE, 6.61 mA/cm2JSC, 0.58 VOC, 56.64% FF). Our analysis indicates that there are three different mechanisms by which MONs can influence the photoactive layer – light absorption, energy level alignment, and morphological changes. Analysis of external quantum efficiency, UV–vis and photoelectron spectroscopy data found that MONs have similar effects on light absorption and energy level alignment. However, atomic force and Raman microscopy studies revealed that the nanosheet thickness and lateral size are crucial parameters in enabling the MONs to act as beneficial additives resulting in an improvement of the OPV device performance. We anticipate this study will aid in the design of MONs and other 2D materials for future use in other light harvesting and emitting devices.

Ultrahighly-efficient and stable luminescent solar concentrators enabled by FRET-based carbon nanodots

Luminescent solar concentrators (LSCs) as an optical device to concentrate light from large areas illuminated by sunlight into small-area photovoltaic cells, can greatly reduce the cost of solar energy generation, thus showing promise in building-integrated photovoltaics. Here, we report the synthesis of a novel type of composite nanoparticle via the simple sol-gel method. Starting from hydroxyl-rich carbon nanodots (CDs), Rhodamine B (RhB) molecules were embedded into a silica matrix shell, forming a composite core-shell system, where the CDs represent the core and RhB embedded in SiO2 are the shell of the final CDs/RhB@SiO2 structure. These nanoparticles were successfully employed in high-performance LSC fabrication. The Förster resonant energy transfer (FRET) between the CDs and the dye was successfully exploited to improve the light absorption efficiency and power conversion efficiency (ηPCE) of LSC devices. The solid-state photoluminescence quantum yield of the as-synthesized composite nanoparticles can reach ∼ 57 % due to the effective suppression of the aggregation-induced quenching. These fluorescent composite nanoparticles were used for fabricating LSC devices with an ultrahigh ηPCE of ∼ 3.8 % for 5 × 5 cm2 devices, thanks to the high loading of luminophores and effective FRET.

Enhancing physicochemical durability and photoelectronic performance beyond bendable large-area organic photoelectronic devices through tailored multilayer interface

Photoelectronic devices, such as organic solar cells (OSCs) and organic photodetector (OPDs), play a crucial role in the development of renewable energy technologies, with an emphasis on achieving high efficiency, photoresponse and mechanical stability. This study presents a novel, annealing-free bilayer electron transport layer (ETL) comprising polyethyleneimine ethoxylated zinc oxide nanoparticles (PE-ZnO) and protonated polyethyleneimine (p-PEIE) for inverted flexible organic photoelectronic conversion devices, with significantly improves overall efficiency and mechanical durability. This novel ETL configuration demonstrated a not only increased the power conversion efficiency (PCE) of flexible OSC devices up to 15.50 %, but also demonstrated outstanding mechanical stability. In addition to bending-flexural stress, where the devices retained 96.95 % efficiency at 0.75 cm radius, sliding-shear stress were also conducted to simulate rollable device conditions. Remarkably, the bilayer ETL maintained approximately 97 % of its initial efficiency after 5000 sliding cycles. Additionally, the large-area flexible OSCs with an active area of 54 cm2, reached PCE of 12.63 %, proving to be 81.5 % as efficient as small-area flexible cells, demonstrating scalability and practical viability. The application of bilayer ETL in flexible OPDs also results in significant reduction in dark current, enhanced photoresponse, and excellent mechanical stability indicating a robust solution for both solar energy harvesting and light sensing technologies. These findings provide a universal solution for improving the physicochemical durability and photoelectronic performance of bendable large-area organic photoelectronic devices.

Ellagic acid/Fe nanocomposite thin film with high power conversion efficiency for photovoltaic devices

This study synthesizes and characterizes an ellagic acid/Fe nanocomposite thin film ([Ellag-A/Fe·6H2O]NCTF) to enhance photovoltaic device efficiency, achieving a notable power conversion efficiency of 14.5 %. Using FT-IR, TGA, XRD, SEM, and optical analyses, the nanocomposite's structural, thermal, and optical properties were investigated, revealing a polycrystalline structure with improved thermal stability over pure ellagic acid. Density Functional Theory (DFT) calculations show a large energy gap of 1.08 eV, indicating stability and high excitation energies. The combination of organic ellagic acid with iron nanoparticles makes ([Ellag-A/Fe·6H2O]NCTF a promising material for photovoltaic applications.

Role of Near-IR Sensitive Asymmetric A-DA′D–π–A-type Non-Fullerene Acceptors for Efficient Organic Solar Cells: A Theoretical Insight

Non-fullerene acceptor (NFA) molecules attracted huge attention from the photovoltaic community for their potential use in organic solar cells (OSCs). Herein, we designed a series of NFA materials (AR1–AR9) for OSCs by altering end-capped moieties. We employed various advanced density functional theory (DFT) and time-dependent (TD-DFT) approaches to characterize this designed AR1–AR9 series. Compared to the synthetic reference molecule ([Formula: see text], designed molecules AR1–AR9 revealed a smaller bandgap (1.85 eV), and improved absorption spectra ([Formula: see text] 741 nm) in comparison to [Formula: see text] ([Formula: see text] 668 nm), indicating the better potential for the tailored molecules. Furthermore, the designed series (AR1–AR9) shows lower reorganization energy values (for holes and electrons) and lower binding energies (0.323 eV), whereas, improved charge mobilities, showing them better candidates for OSCs. Moreover, frontier molecular orbitals (FMO), open-circuit voltages ([Formula: see text] and improved charge-transfer characteristics have also been investigated. These findings revealed that all developed NFAs exhibited a wide range of exciton dissociation constants and enhanced absorption efficiency with a relatively lower LUMO energy level. Therefore, we believe that these materials will be beneficial in boosting the power conversion efficiency (PCE) of OSC devices by improving their optoelectronic and photophysical properties.

Regulation of the Buried Interface to Achieve Efficient HTL-Free All-Inorganic CsPbI2Br-Based Perovskite Solar Cells.

The large voltage loss (Vloss) mainly stems from the mismatch between the perovskite film and electron transport layer in CsPbI2Br-based all-inorganic perovskite solar cells (I-PSCs), which restricts the power conversion efficiency (PCE) of devices. To address this issue, potassium benzoate (BAP) is first introduced as a bifunctional passivation material to regulate the TiO2/CsPbI2Br interface, reduce the Vloss, and improve the photovoltaic performance of CsPbI2Br-based I-PSCs. Eventually, the champion PCE of CsPbI2Br-based I-PSCs without a hole transport layer modified by BAP (Target-PSCs) improves to 14.90% from the 12.14% of reference PSCs. The open-circuit voltage (Voc) increases to 1.27 V from the initial 1.14 V after BAP modification. A series of characterizations show that BAP modification can not only optimize the energy level alignment of I-PSCs but also passivize the surface defects caused by uncoordinated Cs+/Pb2+. Moreover, the Target-PSCs without encapsulation demonstrate better thermal stability, which can maintain 107.6% of the original PCE after annealing at 160 °C for 140 min in humid air. While the reference PSCs only maintain 76.5% of their initial PCE after annealing at the same process. This work provides a simple strategy to modify the buried interface and improve the performance of CsPbI2Br-based I-PSCs.

17.2% Efficiency for Completely Non‐Fused Acceptor Organic Solar Cells Via Re‐Intermixing Strategy in D/A Stratified Active Layer

AbstractPursuing power conversion efficiency (PCE) is the priority of developing organic solar cells (OSCs) based on low‐cost completely non‐fused ring acceptors. Herein, a donor/acceptor re‐intermixing strategy to enhance the photon capturing process, based on a previously established well‐stratified active layer morphology is reported. By adding 20 wt% PTQ10 (polymer donor) into the acceptor's precursor, the device PCE is increased to 16.03% from 15.11% of the D18/A4T‐16 control system, which is attributed to the additional charge generation interface and suppressed bimolecular recombination. On the contrary, using the equal ratio of PM6 leads to significant efficiency loss, indicating the importance of considering vertical distribution from the perspective of thermodynamics. Moreover, a cutting‐edge level of 17.21% efficiency for completely non‐fused ring acceptor systems is realized by altering the active layer to PBQx‐TF/TBT‐26 and PTQ11, via the identical processing strategy. This work thus presents attractive device engineering and solar cell performance, as well as in‐depth vertical morphology understanding.

Magnetron sputtered nickel oxide with suppressed interfacial defect states for efficient inverted perovskite solar cells

Widely used spin-coated nickle oxide (NiOx) based perovskite solar cells often suffer from severe interfacial reactions between the NiOx and adjacent perovskite layers due to surface defect states, which inherently impair device performance in a long-term view, even with surface molecule passivation. In this study, we developed high-quality magnetron-sputtered NiOx thin films through detailed process optimization, and compared systematically sputtered and spin-coated NiOx thin film surfaces from materials to devices. These sputtered NiOx films exhibit improved crystallinity, smoother surfaces, and significantly reduced Ni3+ or Ni vacancies compared to their spin-coated counterparts. Consequently, the interface between the perovskite and sputtered NiOx film shows a substantially reduced density of defect states. Perovskite solar cells (PSCs) fabricated with our optimally sputtered NiOx films achieved a high power conversion efficiency (PCE) of up to 19.93% and demonstrated enhanced stability, maintaining 86.2% efficiency during 500 h of maximum power point tracking under one standard sun illumination. Moreover, with the surface modification using (4-(2,7-dibromo-9,9-dimethylacridin-10(9H)-yl)butyl)phosphonic acid (DMAcPA), the device PCE was further promoted to 23.07%, which is the highest value reported for sputtered NiOx based PSCs so far.

Synthesis of hydrophobic silica without traditional aging process to construct the anti-reflective film with ultralow refractive index for improving power conversion efficiency

The fabrication of anti-reflective films to optimize sunlight utilization encounters various challenges. Herein, we have synthesized modified silica with hydrophobic properties, eliminating the conventional aging process to create an anti-reflective film with an ultralow refractive index of 1.05, marking the lowest value reported to date. This innovative methodology reduces tasks that typically require days or weeks to just a few hours, thereby significantly accelerating production. The power conversion efficiency of the photovoltaic device can increase by 6.2 % when coated with this film. This research not only advances the synthesis of silica but also develops anti-reflective films with record-low refractive indices. This breakthrough represents a substantial contribution, highlighting its significant impact on the photovoltaic field.

Suppressed Ion Migration by Heterojunction Layer for Stable Wide-Bandgap Perovskite and Tandem Photovoltaics.

Wide-bandgap (WBG) perovskite has demonstrated great potential in perovskite-based tandem solar cells. The power conversion efficiency (PCE) of such devices has surpassed 34%, signifying a new era for renewable energy development. However, the ion migration reduces the stability and hinders the commercialization, which is yet to be resolved despite many attempts. A big step forward has now been achieved by the simulation method. The detailed thermodynamics and kinetics of the migration process have been revealed for the first time. The stability has been enhanced by more than 100% via the heterojunction layer on top of the WBG perovskite film, which provided extra bonding for kinetic protection. Hopefully, these discoveries will open a new gate for WBG perovskite research and accelerate the application of perovskite-based tandem solar cells.

Improving Hybrid Tin Halide Films of Lead-Free Perovskite Solar Cells with a Volatile Additive of Dipropyl Sulfide.

Lead-free perovskite solar cells with hybrid tin halides (Sn-PVKs) as harvesters have attracted attention with respect to eliminating the contamination of conventional hybrid lead halides. However, Sn-PVK films usually have inferior performance due to rapid crystallization and uncontrollable morphology. Moreover, Sn2+ ions suffer from irreversible oxidation that results in self-doping and device instability. Additive engineering is a key strategy for improving the quality of Sn-PVK films, but solid residues of additives could degrade the transport-recombination process. In this work, dipropyl sulfide (DPS) was introduced as a volatile additive into the precursor solution, and no residue exists in the Sn-PVK films after thermal annealing. The coordinating ability of DPS molecules stabilized Sn2+ ions to form the intermediate complex, which retards the crystallization and oxidation of Sn-PVK films. Consequently, the power conversion efficiencies of devices increase from 11.0% to 12.9% with less recombination and a lower leakage current, and the stability of the devices is improved simultaneously.

(Invited) Forecasting Hybrid Perovskites’ Dynamic Response through Machine Learning

Machine learning (ML) can significantly accelerate the discovery of materials for clean energy. Hybrid perovskites (an emerging class of materials for photovoltaics and light-emitting diodes) encompass an enormous chemical composition space, resulting in a hyperparameter space that is nearly impossible to be interrogated via traditional trial-and-error methods. Thus, there has been a pressing need within the materials research community to identify ML models that can be implemented to inform the physical and chemical behavior of the perovskites. Here, we apply distinct ML models (mostly based on recurrent neural networks) to classify and forecast physical properties encompassing electrical conductivity, photoluminescence response, the power conversion efficiency of photovoltaic devices, etc. Specifically, we use automated, in situ optical measurements to predict the optical response of a series of perovskites for 50+ hours, upon materials’ exposure to moisture. We quantitatively compare linear regression, echo state network, and seasonal auto-regressive integrated moving average with eXogenous regressor algorithms and achieve accuracy of >90% for the latter. Demonstrating the ability of this model to capture non-linear features. Our high-throughput measurements and ML-assisted data analysis exemplifies the potential of ML to diagnose and forecast hybrid perovskites’ response with a variety of chemical compositions.

Nitrogen-rich carbon dots as the antisolvent additive for perovskite-based photovoltaic devices

Solution-processed perovskite solar cells (PSCs) have demonstrated a tremendous growth in power conversion efficiency (PCE). A high-quality, defect-free perovskite-based active layer is a key point to enhance PSC performance. Introduction of additives and interlayers have proved to be an effective tool to passivate surface defects, control crystal growth, and improve PSC stability. Antisolvent engineering has emerged recently as a new approach, which aims to adjust perovskite layer properties and enhance the PCE and stability of PSC devices. Here, we demonstrate that carbon dots (CDs) may serve as a prospective additive for antisolvent engineering. Nitrogen-rich amphiphilic CDs were synthesized from amines by a solvothermal method and used as an additive to chlorobenzene for a perovskite layer fabrication. The interaction between perovskite and functional groups in CDs promotes improved crystallization of an active perovskite layer and defects passivation, bringing higher PSCs efficiency, stability, and suppressed hysteresis. Under optimized CD concentration, the maximum PCE increased by 34% due to the improved short-circuit current and fill factor, and the device maintains 87% of its initial efficiency after 6 d of storage under ambient conditions.

Crown Ethers with Different Cavity Diameters Inhibit Ion Migration and Passivate Defects toward Efficient and Stable Lead Halide Perovskite Solar Cells.

Organic-inorganic hybrid metal halide perovskite solar cells have been considered as one of the most promising next-generation photovoltaic technologies. Nevertheless, perovskite defects and Li+ ionic migration will seriously affect the power conversion efficiency and stability of the formal device. Herein, we designed two crown ether derivatives (PC12 and PC15) with different cavity diameters, which selectively bind to different metal cations. It is found that PC15 in perovskite precursor solution can actively regulate the nucleation and crystallization processes and passivate the uncoordinated Pb2+ ions, while PC12 at the interface between the perovskite layer and hole-transporting layer can effectively inhibit the migration of Li+ ions and reduce nonradiative recombination losses. Therefore, PC12 and PC15 can act as "lubricant" and defect passivators, as well as inhibitors of ion migration, when they are synergistically applied at the surface and bulk of perovskite layer. Consequently, the optimized device achieved a champion efficiency of 24.8% with significantly improved humidity, thermal, and light stability.

Lattice Strain Regulation and Halogen Vacancies Passivation Enable High-Performance Formamidine-Based Perovskite Solar Cells.

Formamidinium lead iodide (FAPbI3) perovskite has lately surfaced as the preferred contender for highly proficient and robust perovskite solar cells (PSCs), owing to its favorable bandgap and superior thermal stability. Nevertheless, volatilization and migration of iodide ions (I-) result in non-radiating recombination centers, and the presence of large formamidine (FA) cations tends to cause lattice strain, thereby reducing the power conversion efficiency (PCE) and stability of PSCs. To solve these problems, the lead formate (PbFa) is added into the perovskite solution, which effectively mitigates the halogen vacancy and provides tensile strain outside the perovskite lattice, thereby enhancing its properties. The strong coordination between the C═O of HCOO- and Pb-I backbones effectively immobilizes anions, significantly increases the energy barrier for anion vacancy formation and migration, and reduces the risk of lead ion (Pb2+) leakage, thereby improving the operation and environmental safety of the device. Consequently, the champion PCE of devices with Ag electrodes can be increased from 22.15% to 24.32%. The unencapsulated PSCs can still maintain 90% of the original PCE even be stored in an N2 atmosphere for 1440h. Moreover, the target devices have significantly improved performance in terms of light exposure, heat, or humidity.

Effects of hydrazine compounds as additives on the characteristics of organic-inorganic hybrid lead-tin perovskite photovoltaic device

Lead-tin perovskite solar cells (Pb-Sn PSCs) are a more environmentally friendly alternative to the mainstream lead-based PSCs, but their development has been hampered by their instability due to the strong tendency of the Sn2+ constituent to oxidize. This study examines the effects of three types of hydrazine compound—phenylhydrazine hydrochloride (PH•HCl), 4-fluorophenylhydrazine hydrochloride (FPH•HCl), and 1-[2,5-bis(trifluoromethyl)phenyl]hydrazine hydrochloride (BTFMPH•HCl)—as additives to Pb-Sn perovskite precursor solutions on the stability and performance of Pb-Sn PSC devices, taking advantages of the hydrazine functional group’s ability to suppress oxidation of Sn2+, and of the hydrophobicity provided by the phenyl structure and/or fluorine (F) contents of the selected compounds. All of the three additives significantly improved the stability of the resultant Pb-Sn PSC devices, with the additives containing more F contents (BTFMPH•HCl > FPH•HCl > PH•HCl) showing slightly greater improvements. The PH•HCl additive markedly enhanced the power conversion efficiency (PCE) while reducing the hysteresis ratio of the PSC devices thanks to its multifaceted effects including improving morphology, reducing non-radiative losses, alleviating recombination defects, and enhancing charge-carrier mobility of the Pb-Sn perovskite layer, as elucidated by a series of photo-luminescence and electrical characterizations. Both the BTFMPH•HCl and FPH•HCl additives slightly degraded the device PCE due to their poorer resultant perovskite morphology, which was attributed to their lower affinity with the perovskite as a result of their F contents. Our results provide useful insights in selecting and designing hydrazine-based additives for PSC.

Enhanced cation interaction in perovskites for efficient tandem solar cells with silicon.

To achieve the full potential of monolithic perovskite/silicon tandem solar cells, crystal defects and film inhomogeneities in the perovskite top cell must be minimized. We discuss the use of methylenediammonium dichloride as an additive to the perovskite precursor solution, resulting in the incorporation of in situ-formed tetrahydrotriazinium (THTZ-H+) into the perovskite lattice upon film crystallization. The cyclic nature of the THTZ-H+ cation enables a strong interaction with the lead octahedra of the perovskite lattice through the formation of hydrogen bonds with iodide in multiple directions. This structure improves the device power conversion efficiency (PCE) and phase stability of 1.68 electron volts perovskites under prolonged light and heat exposure under 1-sun illumination at 85°C. Monolithic perovskite/silicon tandems incorporating THTZ-H+ in the perovskite photo absorber reached a 33.7% independently certified PCE for a device area of 1 square centimeter.

Optimizing the performance of Inverted FASnI3-based perovskite solar cells by device simulation

Abstract The tin-based PSCs (perovskite solar cells), with low toxicity and excellent photovoltaic properties, offer a promising solution to lead environmental pollution and toxicity issues, emerging as a strong substitute for environmentally friendly lead-free PSCs. However, tin-based PSCs still face significant challenges in terms of low power conversion efficiency and poor long-term stability. Therefore, in-depth research on tin-based PSCs is required to further enhance their performance. In this study, we utilize SCAPS-1D to simulate the currently efficient inverted FASnI3-based PSCs and determine the PSCs device parameters that are as close as possible to the results in published experiments. The simulation results indicate that the parameter adjustment of the absorption layer plays a vital role in the inverted device. Those parameters are thickness, defect density, and doping concentration. Similarly, parameter variations of other layers (parameters such as electron affinity, thickness, and doping concentration) and interfaces (parameters are defect density at different interfaces) are considered. We achieve a final optimized simulated device power conversion efficiency of 18.219%. This research aims to contribute to the future development of inverted FASnI3-based PSCs.

The Near‐Infrared Light Emitted by LiScO2:Cr3+ Phosphor Used to Induce Gland Secretion for Sjogren's Syndrome

AbstractPhotobiomodulation is promisingly used as a noninvasive new weapon against Sjogren's syndrome, which is a disorder of immune system with two main symptoms of dry eyes and a dry mouth. This work reports a new NIR LED device made from LiScO2:Cr3+ phosphor for the application. The absorbance, internal, and external quantum efficiency of the optimal Li(Sc0.98Cr0.02)O2 phosphor reach 40.9%, 34.5%, and 14.1%, respectively; and the output power and energy conversion efficiency of the LED device packaged using the phosphor driven under 20 mA are 4.23 mW, respectively. The emission spectrum of the LED device can well cover the action spectrum of oxidized CuA in cytochrome c oxidase molecules. Both the pathological changes of mice submandibular gland and the expression of human submandibular gland epithelial cells (HSG) in AQP5, M3R andEGR1 confirm that the NIR light has great potential application for treating Sjogren's syndrome. Moreover, study with mice approved that the therapy using the NIR light is more efficient than the conventional medicine treatment using hydroxychloroquine sulfate.

Hierarchical Solid-Additive Strategy for Achieving Layer-by-Layer Organic Solar Cells with Over 19 % Efficiency.

Layer-by-layer (LbL) deposition of active layers in organic solar cells (OSCs) offers immense potential for optimizing performance through precise tailoring of each layer. However, achieving high-performance LbL OSCs with distinct solid additives in each layer remains challenging. In this study, we explore a novel approach that strategically incorporates different solid additives into specific layers of LbL devices. To this end, we introduce FeCl3 into the lower donor (D18) layer as a p-type dopant to enhance hole concentration and mobility. Concurrently, we incorporate the wide-band gap conjugated polymer poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) into the upper acceptor (L8-BO) layer to improve the morphology and prolong exciton lifetime. Unlike previous studies, our approach combines these two strategies to achieve higher and more balanced electron and hole mobility without affecting device open-circuit voltage, while also suppressing charge recombination. Consequently, the power conversion efficiency (PCE) of the D18+FeCl3/L8-BO device increases to 18.12 %, while the D18/L8-BO+PFO device attains a PCE of 18.79 %. These values represent substantial improvements over the control device's PCE of 17.59 %. Notably, when both FeCl3 and PFO are incorporated, the D18+FeCl3/L8-BO+PFO device achieves a remarkable PCE of 19.17 %. In summary, our research results demonstrate the effectiveness of the layered solid additive strategy in improving OSC performance.