Optimal Power Conversion Efficiency Research Articles

Time-resolved cathodoluminescence measurement of the effects of α -particle-related damage on minority hole lifetime in free-standing n-GaN

Time-resolved cathodoluminescence using 30 keV ultrafast electron pulses has been used to perform direct measurements of the minority hole lifetime τh as a function of 3.7 MeV α-particle fluence in high-quality free-standing n-type GaN substrates. The lifetime damage factor K calculated from these measurements was found to monotonically decrease from 6.9 × 10−2 to 6.4 × 10−4 cm2 s−1 ion−1 with increasing α-fluence from 108 to 1012 cm−2, implying a reduction in trap cross section and/or an aggregation of α-induced traps. The small, ∼200–300 nm, hole diffusion length estimated from the minority hole lifetime for the highest α-fluence necessitates the deployment of α-voltaic device strategies and architectures that emphasize depletion and drift over diffusion for effective charge collection and optimal power conversion efficiency.

The Impact of Bromine Surface Doping on the Structural, Optical, and Morphological Properties of Bismuth‐Based Perovskite Film as a Light‐Absorber in Perovskite Solar Cells

Bismuth‐based perovskite materials have concerned significant attention due to their low‐toxic and stable properties. However, achieving smooth and dense thin films for the preferential growth of bismuth‐based perovskite along the c‐axis, which is conducive to the preparation of solar cells, is challenging. Therefore, using halogen atoms to partially replace iodine atoms and constrain anisotropic growth has been shown to be an effective method for obtaining high‐quality perovskite films. Herein, Br doping with varying concentrations is used to treat bismuth‐based perovskite films with larger and denser grains compared to those without doping. When a small amount of Br ions is doped, the surface of the perovskite layer becomes more uniform, significantly improving the compactness of the perovskite film. Additionally, proper Br doping can reduce internal defects in the films, effectively inhibiting nonradiative recombination, enhancing light absorption, and increasing carrier lifetime. The optimal power conversion efficiency of Br‐doped bismuth halide perovskite solar cells is found to be 0.136%, compared to 0.087% for pristine devices.

A mechanistic investigation of non-covalent interactions induced by selenium and alkoxy substitution in the structural and photoelectric properties of non-fused ring electron acceptors

The pivotal role of non-covalent interactions has been increasingly acknowledged by researchers in the intricate design and advancement of non-fused ring electron acceptors (NFREAs). This surge in attention arises from their profound influence on the facilely twisted molecular geometries and critical photoelectric attributes inherent to organic solar cells (OSCs). In this study, various selenium atoms and alkoxy groups were strategically introduced into the well-performing NFREA A4T-16, leading to the creation of molecules denoted as Se-1 to Se-9 and O1 to O9. Utilizing density functional theory (DFT) and time-dependent density functional theory (TD-DFT), a comprehensive analysis of these molecules was conducted, encompassing factors such as intramolecular non-covalent interactions, the fill factor (FF), and the open-circuit voltage (VOC). The electronic structures and photovoltaic characteristics of these molecules underwent a thorough investigation to elucidate the intricate mechanisms governing non-covalent interactions within NFREAs, thereby clarifying their functional significance. The findings disclose that acceptor molecules featuring selenium substitution display notably augmented Se∙∙∙O and S∙∙∙O non-covalent interactions, exceeding the strength observed in their alkoxy-substituted derivatives. This results in the selenium-substituted derivatives boasting superior overall planarity, narrower energy gaps, reduced excitation energies, and broader absorption bandwidths, thereby enhancing their charge transfer characteristics compared to A4T-16. Conversely, the alkoxy-substituted acceptor molecules display higher fill factor (FF) and superior open-circuit voltage (VOC) relative to the selenium-substituted derivatives. Notably, the innermost substitutions at O6, O7, and O9 show the most promising outcomes, potentially indicating optimal power conversion efficiency (PCE).

Exploration of the structural and electrical characteristics and solar cell applications of an electrolyte membrane derived from acacia gum

The natural and eco-friendly solid-state electrolytes were prepared using varying concentrations (wt%) of ZnSO4.7H2O salt and pure acacia gum through the solution cast method. Multiple analytical methods were employed to characterize the resulting acacia gum electrolyte samples. XRD analysis confirmed the increased presence of the amorphous phase with the introduction of salt. FTIR analysis explored the formation of interlinking bands and their complex nature upon salt incorporation. The ionic conductivity was found from room temperature (RT) to 100 °C range. The optimized high ionic conductivity value was found to be 1.11 × 10−4 S/cm at 100 °C for the electrolyte composed of 70 wt% acacia gum and 30 wt% ZnSO4.7H2O, while at RT it was 1.06 × 10−5 S/cm for the same composition. Activation energy values fell within the 0.6–0.92 eV range for all samples. Complex dielectric (real and imaginary) and complex electric modulus analyses were conducted. Dielectric permittivity and electrical modulus analyses revealed a significant interaction between the segmental movements of acacia gum and salt ions. Ionic relaxation processes were explored in terms of conductivity relaxation time using the electrical modulus. The presence of a long tail in the complex dielectric modulus study indicated that the acacia-based solid electrolyte displayed favorable capacitance properties. Further, the Solar Cell (dye-sensitized solar cell) device was fabricated with (Acacia gum + ZnSO4.7H2O) electrolyte. The current density-voltage (J-V) characteristics of the prepared device were investigated. The outstanding results were optimized in the present work, Voc = 0.81 V, Jsc = 9.56 mA/cm2, Fill Factor of 0.67, and optimum power conversion efficiency ƞ = 5.17 % for the electrolyte composed of 70 wt% acacia gum and 30 wt% ZnSO4.7H2O device.

Chalcogenide perovskites for solar energy applications: The role of Sn substitution in BaZrS3-based photovoltaic devices

This study investigates the photovoltaic potential of the chalcogenide perovskite BaZr1-xSnxS3, where x values of 0, 0.125, and 0.250 were chosen. The band gap of BaZrS3 (1.7 eV) is slightly larger than the optimal band gap for single-junction devices, and alloying with Sn has been explored to tune the band gap. The photovoltaic performance of devices with different absorber layers was simulated using the SCAPS-1D solar cell simulator software. The results show that the power conversion efficiency (PCE) increases with increasing Sn content, and the optimal PCE is achieved at x = 0.125. The effects of temperature, work function of the back contact, and band offset at the ETL/absorber and absorber/HTL interfaces on the device performance were also investigated. The results show that the PCE decreases with increasing temperature, and the optimal PCE is achieved at a back contact work function of 4.8 eV. The study shows that tailoring band offset at the ETL/absorber and absorber/HTL interfaces can lead to efficiencies about 20 %, highlighting BaZr1-xSnxS3 as a promising material for future high-efficiency solar photovoltaics.

Enhancing power conversion efficiency of polycrystalline silicon photovoltaic cells using yttrium oxide anti-reflective coating via electro-spraying method

The achievement of optimal performance is a crucial aspect of renewable energy resources. The study attempts to boost the power conversion efficiency of polycrystalline silicon (Si) photovoltaic cells by the application of anti-reflective coating (ARC). The solgel method is employed to synthesize yttrium oxide (Y2O3). The electro spraying method was utilized to apply the ARC on photovoltaic cells. The effect of coating on PV cells were determined through the structural, electrical, optical and thermal analysis. The antireflective material was uniformly applied over the coated substrate for 45 min (Y-I), 90 min (Y-II), 135 min (Y-III), and 180 min (Y-IV). The sample coated for 135 min showed an optimal power conversion efficiency (PCE) of 21.65 % and 20.09 % in the presence of neodymium light and direct sunlight, respectively, and a minimum electrical resistivity of 3.96 × 10−3 Ω-cm. In addition, Y-III coated cells exhibit a maximum absorbance of 94 %. The Y-III coated photovoltaic cells demonstrated the lowest temperature of 34.6 °C when exposed to an open environment and 40.6 °C when exposed to a controlled environment. The results from numerous studies demonstrated that Y2O3 can be a suitable ARC, which effectively improved the efficiency of photovoltaic cells.

Study on the Key Parameters Affecting the Power Conversion Efficiency of Cs2AgBiBr6-Based Perovskite Solar Cells

The lead-free halide double perovskite material A2BB’X6 represented by Cs2AgBiBr6, has higher potential as a photovoltaic material since it has good electronic and optical properties in recent years. However, the highest power conversion efficiency (PCE) achieved for solar cells made with Cs2AgBiBr6 as the light-absorbing layer in experiments is only 2.51%. To investigate this phenomenon, we used the Solar Cell Capacitance Simulator (SCAPS) simulation software to build five solar cell models with the structure of FTO/ZnO/Light-absorbing layer/Cu2O/Au based on different light-absorption layer materials. Two reasons causing the low PCE of Cs2AgBiBr6 solar cells were identified. On the one hand, interlayer defects in Cs2AgBiBr6 film synthesis significantly decreased the fill factor (FF), thereby reducing the quantum efficiency (QE). On the other hand, Cs2AgBiBr6’s larger indirect bandgap resulted in a narrower absorption range. Additionally, it was demonstrated that adjusting the material thickness and alloying method could, respectively, improve the two aforementioned issues. When the thickness of the light-absorbing layer material was 300[Formula: see text]nm, the FF increased from 39.88% to 55.01%, resulting in an optimal PCE of 3.88% for the solar cell. Alloying increased the short-circuit current ([Formula: see text]) from 8.44[Formula: see text]mA/cm2 to 21.24[Formula: see text]mA/cm2, leading to a simulated PCE increase of 8.92% for solar cells based on Cs2NaSb[Formula: see text]In[Formula: see text]I6. This work, from the perspective of device simulation, is highly significant for improving the photoelectric conversion efficiency of Cs2AgBiBr6-based perovskite solar cells in experimental settings. It offers new insights for optimizing solar cell efficiency.

Small molecule perylene diimide derivatives with different bay site modifications as cathode interface layers for organic solar cells

Cathode interface layers (CILs) can effectively elevate the performance of organic solar cells (OSCs), and the development of CILs with high thickness insensitivity is the focus of commercializing OSCs. Perylene diimide (PDI) derivatives proved to be potential CILs, and bay modification could further adjust the coplanarity and optimize the film-forming properties of PDI-based CILs. Thus, two novel CILs with intermediate-sized spacer groups were synthesized (PDINN-P3P and PDINN-TPA). In contrast to PDINN-P3P with m-diphenylbenzene, PDINN-TPA with triphenylamine can form stronger self-doping between the side chain of triphenylamine and the PDI backbone, resulting in higher charge transport capacity and better interface regulation ability. PDINN-TPA-based OSCs demonstrated a higher power conversion efficiency (PCE) of 16.11 % in the PM6:Y6 system, outperforming the PCE of PDINN-P3P-based OSCs (15.00 %). Meanwhile, PDINN-TPA expressed a favorable thickness processing range, a PCE of 14.19 % can be maintained with a thickness up to 35 nm. After storing in the glove box for 114 h, PDINN-TPA-based OSCs can exhibit excellent long-term stability (over 90 % of the optimal PCE). Besides, PDINN-P3P and PDINN-TPA were further utilized CILs in the PM6: BTP-eC9 system, and the PDINN-TPA-based OSCs acquired a PCE of 16.91 % (15.54 % for PDINN-P3P-based OSCs), highlighting the broad applicability of PDINN-P3P and PDINN-TPA. This study confirms that the synergistic effect of bay site modification and n-type self-doping on PDI can simultaneously optimize the thickness insensitivity and long-term stability of PDI-based CILs.

Controlling Water for Enhanced Homogeneities in Perovskite Solar Cells with Remarkable Reproducibility

AbstractTwo‐step sequential deposition of perovskite films is proven efficient and compatible with large‐scale production. Nevertheless, its critically regulated environmental humidity often remains a burden, hindering its applications in reproducible fabrication of perovskite solar cells (PSCs). Herein, by introducing a water ethyl acetate (W‐EA) solution treatment before annealing, improved perovskite crystallinity and homogeneity in FA0.95‐xMAxCs0.05PbI3 films without additional composition regulation is achieved. In situ Grazing‐incidence Wide‐angle X‐ray Scattering experiments highlighted accelerated crystallization kinetics in W‐EA‐treated films, leading to high‐quality perovskite formation. PSCs based on this method reached an optimal power conversion efficiency of 25.01% and demonstrated enhanced moisture resistance, retaining 88% efficiency after 1000 h in ambient conditions. This W‐EA treatment simplifies the fabrication process, greatly reducing the need for controlled humidity, and offers insights into the role of water in perovskite film crystallization, with significant implications to produce high‐performance PSCs.

Asymmetric Alkylthio Branched Chain on Pentacyclic Small Molecular Acceptors Enables High Efficiency Organic Solar Cells

Solution‐processible organic solar cells (OSCs) have gained much attention as one of the most promising options for sustainable energy. With rapidly increasing efficiency of OSCs, developing small molecular acceptors (SMAs) with simple molecular structures are critical for reducing the cost of photovoltaics. Herein, three new SMAs (BZ4F‐C2SEH, BZ4F‐2C2SEH, BZ4F‐SEH) are designed by the incorporation of ethyl(2‐ethylhexyl)sulfane or (2‐ethylhexyl)‐sulfane at the β‐position of thiophene. As a result, the BZ4F‐C2SEH‐based devices obtained an optimal PCE of 15.08% with a good balance between open‐circuit voltage (Voc = 0.87 V) and short‐circuit current density (Jsc = 23.27 mA cm−2) by blending with low‐cost polymer donor PTQ10. Besides, the BZ4F‐C2SEH based devices treated by thermal annealing (TA) and solvent annealing (SVA) deliver a satisfactory power conversion efficiency (PCE) of 16.18% with a Voc of 0.88 V, and a Jsc of 23.98 mA cm−2. This work highlights that attaching asymmetric alkylthio side chain at the β‐position of thiophene can be used as an effective molecular design strategy to trade off Voc and Jsc, thus improving the photovoltaic performance of OSCs.

Impact of pre and post-perovskite infiltration treatments on monolithic perovskite solar cell performance

Carbon-based monolithic perovskite solar cells (mPSCs) represent an enticing frontier in the domain of organic–inorganic hybrid solar cells, capturing substantial research attention due to their cost effectiveness and straightforward fabrication process. Despite these merits, the challenge of achieving uniform pore filling in mPSCs, especially within mesoporous layers comprising titania, zirconia, and carbon alongside perovskite, persists. The uncontrolled and confined crystallization of the perovskite precursor within these mesoporous layers warrants meticulous investigation. This study addresses the issues related to uncontrolled crystallization by employing temperature-assisted infiltration techniques spanning from room temperature to 70 °C across triple mesoporous scaffolds. Devices were intricately fabricated using a semi-automatic drop-casting procedure, incorporating a (5-AVA)x(MA)1−xPbI3-mixed cation perovskite. Following infiltration, comprehensive pore filling of oxide layers was achieved through chlorobenzene-assisted antisolvent treatment. Comparisons were made between chlorobenzene-assisted and untreated samples under ambient conditions and thermal stress (40–70 °C). The temperature-dependent effects on perovskite infiltration and recrystallization were systematically investigated through dark and light current–voltage (J–V) characteristics, Impedance Spectroscopy (IS), and X-ray Diffraction (XRD) analyses. The findings revealed that the optimum power conversion efficiency (PCE) of 13.34% was attained when perovskite infiltration occurred at 40 °C with antisolvent treatment. Dark J–V and IS results indicated that temperature-assisted infiltration not only stimulated charge transfer but also effectively suppressed recombination. Under chlorobenzene treatment, XRD peaks exhibited broadening, indicating a reduction in perovskite crystallite size. This phenomenon facilitated the development of perovskite crystals across all available mesoporous spaces, leading to an enhanced interface property conducive to efficient charge transfer. The insights gleaned from this study on the controlled crystallization of perovskite precursors within mesoporous layers hold significant promise for advancing the stability and efficiency of mPSCs.

Effect of ball milling time on Sr0.7Sm0.3Fe0.4Co0.6O2.65 perovskites and their application as semiconductor layers in dye-sensitized solar cells

The practical utilization of TiO2 as a semiconductor in dye-sensitized solar cells (DSSCs) has been set back by poor visible light absorption, high charge carrier recombination, and low electrical conductivity, which reduce the power conversion efficiency (PCE) and sustainability of the device. In this respect, perovskites with excellent properties, such as large surface area, good optical properties, high electrical conductivity, and superior electrochemical stability, have recently emerged as promising alternatives capable of overcoming the drawbacks of TiO2. Herein, Sr0.7Sm0.3Fe0.4Co0.6O2.65 (SSFC) perovskites were prepared via the ball milling method at various milling times of 0, 5, and 10 h, and the obtained samples were denoted by SSFC-0, SSCF-5, and SSCF-10, respectively. Increasing the ball milling time led to a significant reduction in nanoparticle size and agglomeration, which, in turn, increased the surface area and electrical conductivity of the samples. As a consequence, the SSFC-10 perovskite exhibited the smallest average particle sizes (18.9 nm) with the largest surface area (61.8 m2 g−1) and minimum defects, which allowed for efficient electron transport, resulting in the best electrical conductivity of 49.8 S cm−1. Ultimately, DSSCs fabricated using SSFC-10 semiconductor layers achieved an optimum PCE of 6.01 %, which is an improvement of 8.67 %, 1.1 %, and 6.56 % for SSFC-0 (3.69 %), SSFC-5 (4.96 %), and TiO2 (5.64 %), respectively. Thus, varying the ball milling time can be used as an effective technique to tailor the physicochemical properties of SSFC to suit desired applications, particularly the fabrication of highly efficient and sustainable DSSC semiconductor layers.

Inhomogeneous Halide Anions Distribution along Out-of-Plane Direction in Wide-Bandgap Perovskite Solar Cells and Its Effect on Open Circuit Voltage Loss and Phase Segregation.

The large open circuit voltage (VOC) loss and phase segregation are two main obstacles hindering the development of wide-bandgap perovskite solar cells (PSCs). Even though substantial progress has been made through crystallization regulation and surface modification on perovskite, the mechanism of VOC loss and phase segregation has rarely been studied. In this paper, we first investigate the halide ions distribution along the out-of-plane direction and find the initial inhomogeneous distribution of halide ions during the crystallization process is an important reason. It leads to the formation of an unfavorable potential well in PSCs, resulting in VOC loss as well as generation of strong strain exacerbating phase segregation. Through introducing melatonin (MT) into perovskite precursors, a homogeneous distribution of halide anions is realized due to the well-regulated crystallization. Consequently, the treated PSCs exhibit an optimized power conversion efficiency (PCE) of 22.88% with a VOC loss as low as 0.38 V, which are the best values for wide-bandgap PSCs up to now.

N-type small molecule electrolyte cathode interface layer with thickness insensitivity for organic solar cells

Interface engineering has a critical impact on the performances of organic solar cells (OSCs). And cathode interface layer (CIL) with thickness insensitivity is urgently pursued to improve the possibility of industrialization of OSCs. N-type self-doping has been proven effective in increasing electron mobility. Here, four novel n-type small molecule electrolytes (SMEs) with diverse counter anions (CAs), PDIN-BF4, PDIN-BPh4, PDIN-BPhF4, and PDIN-BIm4 were synthesized and employed as cathode interface layers (CILs). Among them, PDIN-BIm4-based OSCs with PM6:Y6 active layer achieved the most glorious electron mobility and thickness insensitivity with a power conversion efficiency (PCE) of 16.98 % due to outstanding self-doping effect and interfacial regulation ability. However, the multi-F atoms on PDIN-BPhF4 may prevent self-doping progress and impede electron transport, thus leading to a low PCE of 11.53 %. Meanwhile, the PDIN-BIm4-based device can maintain over 80 % of the optimal PCE with a thickness of 43 nm or storing in a glove box for 600 h. In addition, PM6: BTP-eC9-based device with PDIN-BIm4 CIL acquired a PCE of 17.82 %, highlighting the broad applicability of PDIN-BIm4. Our work demonstrates that the introduction of CAs into n-type organic materials helps promote the progress of efficient and stable OSCs.

Surface plasmon resonance synergistic coupling effects of gold nanoparticulates with silver grating in P3HT: PC61BM-based organic solar cell

A systematic study was carried out to observe possible boosts in the performance of poly-(3-hexyl thiophene):phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) based organic solar cell via synergistic coupling of plasmonic effects. Various volume concentration ratios of gold nanoparticles and nanorods ranging from 2%, 4%, 6%, and 8% were used to determine an optimum condition. An indicative 2% optimum condition led to synergistic tests. The synergistic coupling of gold nanorods with backcontact grating revealed a power conversion efficiency (PCE) of 4.88%. Since post-thermal annealing process results in optimum interfacial surface morphology and structural reorganization, a post-process hypothesis was performed to observe the behavior of the devices at RT with further comparisons at 40 °C. A further increase in the initial performance of the devices was observed with an optimum PCE of 5.43%. The behavior in the performances revealed stable measurements mostly attributed to conditions below the glass transition temperature of P3HT:PC61BM.

Effects of water additive and moisture on the performance of Dion-Jacobson perovskite [C6H4(CH2NH3)2](CH2NH3)3Pb4I13 solar cells

This work applies comprehensively researches on the influence of water as an additive in precursor solution, and the moisture (65 % relative humidity) on the performance of Dion-Jacobson (DJ) perovskite [C6H4(CH2NH3)2] (CH2NH3)3Pb4I13 solar cells. The results indicate that 3 %−15 % (v/v) water as an additive has minor effect on the power conversion efficiency (PCE) of fresh prepared solar cells, but it can improve the resistance of device to humidity. More importantly, with an appropriate ratio of water additive and moister action time, the perovskite film shows a smoother surface, higher coverage, and better crystallinity, resulting in an optimal PCE of ∼ 8 %, compared to ∼ 1 % of fresh prepared one. Our results are helpful to understand the effect of water and moisture on DJ perovskite solar cells, may contributing to develop rational strategies to improve devices’ stability under humidity ambient.

Tunable electronic and photoelectric properties of Janus group-III chalcogenide monolayers and based heterostructures

Janus group-III chalcogenide monolayers and based heterostructures with breaking vertical structural symmetry offer additional prospects in the upcoming high-performance photoelectric devices. We studied the geometrical, electronic, and photoelectric properties of Janus group-III chalcogenide monolayers and heterostructures. The most energy favorable stacking design of ten vertical heterostructures are considered. The results showed that the Janus Se-In-Ga-S and S-In-Ga-Se monolayers exhibit semiconducting characteristics with the band gaps of 1.295 eV and 1.752 eV, respectively. Furthermore, the different stacking configurations and surface termination at interface can realize the transition of band alignment between type I and type II due to the interlayer coupling. Moreover, we systematically investigated the photoelectric properties of Janus group-III chalcogenide heterostructures and predicated an optimized power conversion efficiency of 16.2%. These findings can aid in comprehending the customized characteristics of Janus group-III chalcogenide heterostructures, offering theoretical guidance for creating innovative photoelectric devices.

Formation of a potential barrier by a ZnSXSe1−X electron-blocking layer to improve the efficiency of CdSe0.3S0.7/CdSe quantum dot sensitized solar cells

We designed and fabricated multilayer quantum dots sensitized solar cells (QDSCs) with TiO2 NPs/CdSe0.3S0.7/CdSe/ZnSXSe1−X, X = S/S + Se = 0, 0.7, 0.8, 0.9, and 1 photoelectrodes to achieve optimum power conversion efficiency (PCE). In the corresponding structure, incoming light is absorbed by the CdSe0.3S0.7 and CdSe quantum dots (QDs), while the ZnSXSe1−X QDs act as an electron blocking layer or passivation layer, forming an energy barrier that restricts electron mobility from the light absorbers to the polysulfide electrolyte. The beneficial effect of the alloyed ZnSXSe1−X layer is the adjustability of its nanoparticle size/bandgap energy proportional to variations in the concentration of anionic precursors X, according to optical results. The PCE value of the reference cell with the TiO2 NPs/CdSe0.3S0.7/CdSe photoanode is 4.15 %. Following the coating of ZnSe, ZnS0.7Se0.3, ZnS0.8Se0.2, ZnS0.9Se0.1, and ZnS QDs via two successive ionic layer adsorption and reaction (SILAR) cycles (2Sc) on the CdSe0.3S0.7/CdSe co-sensitized photoelectrode increasing stability and improving the PCE value to 4.9 %, 5.40 %, 5.70, 5.25 %, and 5.05 %, respectively. Next, by modifying the thickness of the champion cell's passivation layer, the QDSCs with TiO2 NPs/CdSe0.3S0.7/CdSe/ZnS0.8Se0.2 (3Sc) photoelectrode exhibit maximum photovoltaic performance parameters of short circuit current density (JSC) = 26.25 mA/cm2, open circuit voltage (VOC) = 560 mV, fill factor (FF) = 0.42 % and PCE = 6.15 %. This improvement in performance is the result of decreased internal energy loss and recombination of charge carriers at the interface between the electrolyte and photoelectrode, which increases electron collection efficiency and electron injection efficiency in the visible region according to the external and internal quantum efficiency curves.

Performance Potential for Locally Contacted Perovskite Solar Cells

In perovskite solar cells (PSCs), a common characteristic of highly effective interface passivation materials is low conductivity. Gains in voltage are thus often disproportionately offset by resistive losses. Local contact approaches can minimize this trade‐off and have a proven track record in conventional silicon photovoltaics. Indeed, recent record efficiencies for centimeter‐scale PSCs exploit architectures where the passivation layer partially covers the perovskite‐transport layer interface. Herein, a three‐dimensional numerical device model is used to determine practical performance limits to local contact geometries and consider both the optimum contact dimensions and the trade‐offs involved in relaxing these dimensions for ease of fabrication. It is observed that the potential for substantial power conversion efficiency (PCE) increases with local contacts. In devices where power loss occurs solely through recombination at the contacted interface, PCE can be enhanced by up to 10% absolute compared to a full‐area contact. However, optimum PCEs depend on contacts on the order of nanometers. It is shown that more fabrication‐friendly micrometer‐scale contacts still boost PCE, but the absolute enhancement falls short due to the relatively low bulk perovskite charge carrier diffusion length. This may ultimately motivate methods of interface engineering that produce “effective” local contact geometries at nanometer scales, such as via self‐forming layers.

Design of non-fused ring electron acceptors with “embracing-type” side chains for organic solar cells

Backbone planarity is an inherent structural feature for fused ring electron acceptors and one of important prerequisites for their high photovoltaic performance. However, for non-fused ring electron acceptors (NFREAs), it is a challenging task to achieve it. In this work, two NFREAs (Ph2TIC and BT2TIC) containing thiophene-benzene-thiophene or thiophene-benzothiadiazole-thiophene three non-fused aromatic rings in central scaffold were designed with an attempt to use a pair of 2,4,6-triisopropylphenyl substituents (referred as “embracing”-type side chains) at 3,3′-positions of the two thiophene units to lock the backbone in a planar conformation. X-ray crystallography revealed that Ph2TIC has a quasi-planar backbone, whereas BT2TIC shows a twisted one, but both tend to form two-dimensional layered arrays through intermolecular π-π stacking involving terminal acceptor moieties. UV–vis light-absorption spectroscopy showed that both compounds have similar optoelectronic properties either in dilute solutions or in solid film state, thus confirming the conformation-lock function of the “embracing”-type side chains. While for photophysical properties, BT2TIC displays a red-shifted broader light absorption spectrum as compared to Ph2TIC due to the introduction of an additional acceptor moiety in the structure. Ph2TIC and BT2TIC were evaluated as the acceptor materials in organic solar cells in combination with PM6, a typical donor polymer, and delivered the optimized power conversion efficiencies of 4.31 % and 3.78 %, respectively. Although the photovoltaic performances are modest, the work provides a new thought for maintaining the backbone planarity in NFREAs and would be useful in their future design.