C60 Layer Research Articles

Delamination of Perovskite Solar Cells in Thermal Cycling and Outdoor Tests

For the commercialization of perovskite solar cells (PSCs), detection of associated degradation mechanisms and mitigation of their effect is of paramount importance. The former requires outdoor and indoor stability tests to detect these mechanisms under real operation conditions and to accelerate them under controlled environments. Herein, the thermomechanical stability of encapsulated PSCs in outdoor tests at three locations coupled with indoor thermal cycling tests is investigated. Results show that encapsulant‐induced partial delamination can occur in outdoor and indoor tests, leading to disruption in device integrity and substantial loss in the cell active area and short‐circuit current. The findings suggest that delamination involves C60 and SnO2 layers as the mechanically weakest point in the device stack. To the best of our knowledge, this work is the first demonstration of delamination in encapsulated PSCs under real operation conditions. While partial delamination emerged on some of the cells exposed in Israel and Cyprus in just a few weeks, it did not occur in Germany over 2.5 years of outdoor exposure. This highlights the importance of multiclimate outdoor testing to validate the significance of failure modes observed through accelerated indoor testing.

Organic heterojunction memristors with enhanced tunable resistive states for artificial synapses

Tunable and uniform evolution of conductance is the key performance metric for neuromorphic computing leveraging memristors. Nonetheless, the stochastic conductance update associated with limited material composition and uncontrollable filament distribution has restricted the tunability that can be customized for targeted synaptic properties. Here, we introduce organic heterojunction memristors utilizing the C60/P3HT bilayer, demonstrating analog switching characteristics with multilevel conductance states. We demonstrate that both conventional bipolar and unipolar voltages can achieve synaptic plasticity modulation for potentiation and depression, offering enhanced tunability. Through in situ Raman spectroscopy and impedance spectroscopy, we directly observe the dynamic alterations within the active layers during switching processes. The reversible migration of ions diminishes the barrier within the polymer layer, leading to highly uniform resistive switching behavior. The C60 layer functions as a confined transport medium, mitigating critical current variability issues. Moreover, we introduce a shunt resistor approach, furnishing analog memristors with selectively adjustable uniformity, enhanced linearity, and expanded dynamic conductance range, providing a general solution adaptable to various memristive hardware architectures.

DFT and SCAPS-1D based optimization study of double perovskite Cs2AuBiCl6 solar cells utilizing different charge transport layers

In this work, halide double perovskite (HDP) Cs2AuBiCl6 is investigated as potential absorber material in the perovskite solar cell (PSC) using the SCAPS-1D tool. WIEN2K code is utilized for computation to study the structural, and optoelectronic properties of Cs2AuBiCl6. The calculated bandgap of the Cs2AuBiCl6 is found to be ∼1.09 eV using TB-mBJ (Tran-Blaha modified Becke-Johnson) potential. Performance of the Cs2AuBiCl6-based PSC is enhanced by improving the properties of charge transport layers and the perovskite (PVSK) absorber layer. Combination of Electron Transport Layers (ETLs) such as WS2, PCBM, ZnO, TiO2, and C60 and Hole Transport Layers (HTLs) such as Cu2O, P3HT, CuSCN, PEDOT: PSS, Spiro-OMeTAD, CuSbS2 are evaluated to find the best ETLs and HTLs among the above-mentioned materials. Also, further study is performed on the five best devices with five different ETLs using CuSbS2 as the HTL. Apart from that, the energy band diagrams of the best five devices are investigated. Further, a performance study is done on those best five devices through the impact of the variations in thickness of ETL, defect density, thickness of Cs2AuBiCl6 layer, shunt, and series resistances of device. After all the optimizations, the best PCEs of these five optimized devices are found to be 21.16 %, 21.14 %, 20.84 %, 20.79 %, and 14.75 % with CuSbS2 as HTL, and C60, WS2, TiO2, PCBM, and ZnO as ETLs, respectively. Furthermore, current density-voltage (J-V) and quantum efficiency (QE) characteristics of the five devices are analyzed to determine the potential of Cs2AuBiCl6 as a viable material for non-leaded PSCs.

Comparative examination of both spectral properties and hybrid solar cell application of 2,4,6-trimethoxyphenoxy substituted phthalocyanine dyes

In this study, novel octa 2,4,6-trimethoxyphenoxy substituted phthalocyanines, and tetra chloro and tetra 2,4,6-trimethoxyphenoxy substituted phthalocyanines were synthesized, characterized, examined their spectral properties comparatively and investigated of hybrid solar cell application of them. The spectral characterizations can be performed for all phthalocyanine compounds, solar cell application was only possible for tetra chloro tetra 2,4,6-trimethoxyphenoxy substituted phthalocyanines, the others phthalocyanines not due to their low yield.Solar cell properties of the tetra chloro tetra 2,4,6-trimethoxyphenoxy substituted phthalocyanines were studied using the ITO/ZnO/C60/ P3HT /LiF/Al structure. In order to improve and compare performance parameters of the poly(3-hexylthiophene) (P3HT) based solar cells, the tetra chloro tetra 2,4,6-trimethoxyphenoxy substituted H2Pc (2), Co(II)Pc (3) and Ni(II)Pc (4) compounds were incorporated individually into the solar cell structure between ZnO and C60 layers in which amorphous ZnO nanoparticles serves as electron transfer layer. Solar cell performance parameters such as short circuit current density (JSC), open circuit voltage (VOC), fill factor (FF) and power conversion efficiency (η) were studied as comparison parameters. Incorporation of Ni(II)Pc (4) into the reference structure between ZnO and C60 caused an increase 23.4 % in Jsc and 4.4 % in η whereas incorporation of Co(II)Pc (3) layer into the reference structure caused an increase 135.0 % in Jsc and 107.0 % in η under an illumination of 100 mW/cm2 with an AM 1.5G solar simulator. The best JSC and η (%) values were obtained for P3HT based solar cells with Co(II)Pc (3) interlayer.

Reducing Voltage Loss via Dipole Tuning for Electron‐Transport in Efficient and Stable Perovskite‐Silicon Tandem Solar Cells

AbstractC60 is a widely used electron selective material for p–i–n perovskite cells, however, its energy level does not match well with that of a wide‐bandgap perovskite, resulting in low open‐circuit voltage (VOC) and fill factor (FF). To overcome this issue, ultra‐thin LiF has been widely used as an interlayer between C60 and perovskite layers facilitating efficient electron extraction but resulting in instability. In this work, the use of a piperidinium bromide (PpBr) is reported as an interlayer between C60 and perovskite, and the interlayer further is optimized by introducing an additional oxygen atom on the opposite side of the NH2+. This results in morpholinium bromide (MLBr) with increased dipole moment. Because of this, MLBr is highly effective in minimizing the energy band mismatch between perovskite and C60 layer for electron extraction while at the same time passivating defects. The champion single junction 1.67 eV MLBr solar cell produced a PCE of 21.9% and the champion monolithic MLBr perovskite‐Si tandem cell produced a PCE of 28.8%. Most importantly, both encapsulated MLBr and PpBr devices retain over 97% of their initial efficiency after 400 thermal cycles (between −40 and 85 °C), twice the number of cycles specified by the International Electrotechnical Commission (IEC) 61215 photovoltaic module standard.

Novel dual absorber configuration for eco-friendly perovskite solar cells: design, numerical investigations and performance of ITO-C60-MASnI3-RbGeI3-Cu2O-Au

Perovskite solar cells (PSCs) are increasingly being used as the foundation of the worldwide photovoltaic (PV) industry because of their cost-effective production and durable stability. Perovskite materials, both organic and inorganic, possess distinct optical, mechanical, and electrical properties, such as a high absorption coefficient, a customizable band gap, and a synthesis method based on solutions. This study employed numerical investigations to devise and propose innovative solar cell configurations utilizing the SCAPS-1D simulator. This research presents a Perovskite solar cell design comprising an ITO-C60-MASnI3-RbGeI3-Cu2O-Au solar cell configuration. The unique arrangement of this setup incorporates the use of Indium Tin-oxide (ITO) as the upper contact layer, which is directly exposed to light. The electron transport layer (ETL) is composed of a 0.030 μm thick layer of C60, while the light-harvesting/absorber layers are made up of MASnI3 and RbGeI3, each with a thickness of 0.4 µm. A layer of Cu2O with a thickness of 0.12 μm is employed as the hole transport layer (HTL), whereas the back-contact layer consists of Au. A comparison research was conducted to examine the optimal device configuration. Comprehensive studies are performed to assess the effects of different variables on optimized device performance and power conversion efficiency (PCE). These factors include interface defect densities, thicknesses of different structural layers, band gaps, series and shunt resistance, and operational temperature. The current density (Jsc) is calculated as 32.7 mA/cm2 at an open circuit voltage (Voc) of 0.914 V. Additionally, we observed a power conservation efficiency (PCE) of 20.19 % and an improved fill factor (FF) value of 65.49 %. The ongoing investigations are likely to be valuable for the development and production of cost-effective and high-performance PSCs.

Analysis of lead free CsSnBr3 based perovskite solar cells utilizing numerical modeling

In this study, we propose several CsSnBr3-based PSC configurations using the Solar Cell Capacitance Simulator (SCAPS-1D), incorporating various efficient Electron transport layers (ETLs) such as TiO2, PCBM, WS2, SnO2, ZnO, IGZO, C60, and Hole transport layers (HTLs) like CBTS, CFTS, CuO, CuI, Spiro-OMeTAD, PEDOT:PSS, P3HT, CuSbS2, CuSCN, and Cu2O. Numerical simulation results reveal that the device structure ITO/WS2/CsSnBr3/Cu2O/Au exhibits outstanding power conversion efficiency (PCE), retaining the closest photovoltaic parameter values among 70 different configurations. In this configuration, WS2 served as the ETL, and Cu2O acted as the HTL. This device achieved an outstanding peak PCE of 20.02%. It also boasted a high open circuit voltage (Voc) of 1.23 V, a short circuit current density (Jsc) of 19.32 mA cm−2, and an impressive fill factor (FF) of 84.18%. In comparison, devices utilizing materials like TiO2, PCBM, SnO2, ZnO, IGZO, and C60 yielded PCE values of 19.72, 19.73, 19.72, 19.73, 19.72, and 15.60%, respectively. Furthermore, for the seven best-performing configurations, we investigated the effects of CsSnBr3 absorber thickness, absorber-acceptor doping density (NA), conduction band offset (CBO), ETL doping density (ND), Capacitance–Voltage (C-V), Mott–Schottky (M-S) characteristics, generation and recombination rates, series resistance (Rse), shunt resistance (Rsh), temperature, current–voltage characteristics (J-V), and quantum efficiency (QE) on performance metrics. Our findings indicate that all seven ETLs, when combined with Cu2O HTL, can serve as excellent materials for fabricating high-efficiency CsSnBr3-based PSCs with the ITO/ETL/CsSnBr3/Cu2O/Au structure. To validate our results, we compared the simulation outcomes obtained with SCAPS-1D for the best seven CsSnBr3-PSC configurations with previously published research works. This comprehensive simulation study opens a promising avenue for the cost-effective production of high-performance, lead-free CsSnBr3-based PSCs, contributing to a greener and pollution-free environment.

Interface Reactive Sputtering of Transparent Electrode for High-Performance Monolithic and Stacked Perovskite Tandem Solar Cells.

Sputtered indium tin oxide (ITO) fulfills the requirements of top transparent electrodes (TTEs) in semitransparent perovskite solar cells (PSCs) and stacked tandem solar cells (TSCs), as well as of the recombination layers in monolithic TSCs. However, the high-energy ITO particles will cause damage to the devices. Herein, the interface reactive sputtering strategy is proposed to construct cost-effective TTEs with high transmittance and excellent carrier transporting ability. Polyethylenimine (PEI) is chosen as the interface reactant that can react with sputtered ITO nanoparticles,so that, coordination compounds can be formed during the deposition process, facilitating the carrier transport at the interface of C60/PEI/ITO. Besides, the impact force of energetic ITO particles is greatly alleviated, and the intactness of the underlying C60 layer and perovskite layer is guaranteed. Thus, the prepared semitransparent subcells achieve a significantly enhanced power conversion efficiency (PCE) of 19.17%, surpassing those based on C60/ITO (11.64%). Moreover, the PEI-based devices demonstrate excellent storage stability, which maintains 98% of their original PCEs after 2000 h. On the strength of the interface reactive sputtering ITO electrode, a stacked all-perovskite TSC with a PCE of 26.89% and a monolithic perovskite-organic TSC with a PCE of 24.33% are successfully fabricated.

A Crystalline 2D Fullerene‐Based Metal Halide Semiconductor for Efficient and Stable Ideal‐bandgap Perovskite Solar Cells

AbstractDespite advances in mixed tin‐lead (Sn‐Pb) perovskite‐based solar cells, achieving both high‐efficiency and long‐term device stability remains a major challenge. Current device deficiencies stem partly from inefficient carrier transport, originating from defects and improper band energy alignment among the device's interfaces. Developing multifunctional interlayer materials simultaneously addressing the above concerns poses an excellent strategy. Herein, through molecular and crystal engineering, an amine‐functionalized C60 mono‐adduct derivative (C60‐2NH3 = bis(2‐aminoethyl) malonate‐C60) is utilized for the synthesis of the first crystalline fullerene‐based 2D metal halide semiconductor, namely (C60‐2NH3)Pb2I6. Single crystal XRD studies elucidated the structure of the new material, while DFT calculations highlighted the strong contribution of C60‐2NH3 to the electronic density of states of the conduction band of (C60‐2NH3)Pb2I6. Utilization of C60‐2NH3 as an interlayer between a FA0.6MA0.4Pb0.7Sn0.3I3 perovskite and a C60 layer offered superior band energy alignment, reduced nonradiative recombination, and enhanced carrier mobility. The corresponding perovskite solar cell (PSC) device achieved a power conversion efficiency (PCE) value of 21.64%, maintaining 90% of its initial efficiency, after being stored under a N2 atmosphere for 2400 h. This work sets the foundation for developing a new family of functional materials, namely Fullerene Metal Halide Semiconductors, targeting applications from photovoltaics to catalysis, transistors, and supercapacitors.

Improved performance of inorganic CsPbI3 perovskite solar cells with WO3/C60 UTL bilayer as an ETL structure: a computational study

CsPbI3, also known as cesium lead iodide, has garnered significant attention as a potential absorber in perovskite solar cells (PSCs). CsPbI3-PSCs have not matched the high performance of hybrid PSCs. This study aimed to identify an effective combination of charge transport layers. Six-hole transporting layers (HTLs) including Spiro-OMeTAD, Cu2O, CuO, CuAlO2, CuSbS2, and SrCu2O2, as well as five electron transporting layers (ETLs) such as TiO2, WO3, ZnO, IGZO, and CdZnS, were tested separately in 30 PSCs. The findings of this research indicate that CuAlO2 as the HTL and WO3 as the ETL that are the most appropriate materials among the options examined, so we use FTO/WO3/CsPbI3/CuAlO2/Au as a required PSC. In this research, we used SCAPS (Solar Cell Capacitance Simulator)−1D device modeling to investigate the bilayer ETL of inorganic CsPbI3-PSC and discover the methods to improve their efficiency. In planar PSCs, optimizing electron–hole pair extraction and recombination at the ETL/perovskite interface is crucial for achieving high performance. The key concept is to enhance the WO3/perovskite interface properties by adding a 5 nm ultra-thin layer (UTL) of C60. The bilayer structure WO3/C60 was found to have the advantage of high electron extraction and low interfacial recombination, primarily due to more effective energy level alignment and defect passivation. To achieve the superior efficiency of PSC, various factors such as defect and doping densities in all layers, the energy level alteration of ETL and HTL, interface defect densities on both ETL and HTL sides, back metal contact, operating temperature, and parasitic resistances were optimized. After optimizing these parameters, the efficiency of the system containing WO3/C60 bilayer ETL was found to be 29.39%. The current work proposes a straightforward and promising method to create photovoltaic devices, especially for many types of perovskites, with desirable charge transport layers and recombination properties.

Precise control of hole transport layer integration on PDTS-DTTFBT: PC71BM organic solar cells

Efforts to enhance the commercial viability of organic solar cells (OSCs) prioritize high power conversion efficiency(PCE). This study proposes precision tuning of the photoactive layer thickness in the nanoscale as an innovative method to boost efficiency. Utilizing PDTS-DTTFBT: PC71BM, an organic blend, as the active layer aims to capture a broad photon range while addressing optical losses due to low-energy photons rather than mere absorption. The study integrates PEDOT: PSS and molybdenum trioxide (MoO3) as hole transport layers, alongside C60, PC60BM, and ZnO electron transport layers. Meticulous analysis of their photon absorption, reflectance, charge carrier generation, and localized energy variance emphasizes their impact on the efficiency of PDTS-DTFFBT: PC71BM active films. Notably, incorporating MoO3 as the hole transport layer significantly mitigated losses and altered localized energy, culminating in an impressive 17.69% efficiency at an optimized blend thickness of 120 nm. Augmenting blend thickness directly boosts PCE and current density until reaching optimal thickness, while diminishing fill factor, with minimal effect on open-circuit voltage. These results highlight the efficacy of this methodology in enhancing the performance of organic solar cells.

Numerical simulation and performance optimization of all-inorganic CsGeI3 perovskite solar cells with stacked ETLs/C60 by SCAPS device simulation

Perovskite solar cells, particularly those featuring CsGeI3 as the absorption layer, are distinguished by their non-toxicity and inherent stability. In this work, to optimize the interface contact of the cells, enhance their built-in electric field, and consequently augment the power conversion efficiency, a C60 layer was incorporated into the electronic transport layer. This incorporation led to the formation of a novel dual-electron transport layer structure. Employing SCAPS-1D simulation software, a range of electron and hole transport layer combinations was explored. The optimal configuration was determined to be FTO/SnO2/C60/IDL1/CsGeI3/IDL2/Cu2O/Au. The absorption layer's thickness, doping concentration, defect density, and bandgap were optimized. Furthermore, an investigation was conducted on the performance implications arising from alterations in the dual electron conduction layer SnO2/C60's thickness, bandgap, and doping concentration. Concurrently, adjustments were made to refine the defect density in the interface defect layer, and an investigation was carried out to determine the optimal operational temperature. These endeavors culminated in the achievement of an impressive 30.34% optimal power conversion efficiency, representing a significant 54.25% enhancement over the pre-optimization efficiency of 19.67%. This work stands as a valuable reference for subsequent investigations into the dual electron transport layer structure in Ge-based perovskite solar cells.

Photoemission spectroscopy and microscopy for Ta@Si16 superatoms and their assembled layers.

Superatoms (SAs) with specific compositions have the potential to significantly advance the field of nanomaterials science, leading to next-generation nanoscale functionalities. In this study, we fabricated assembled layers with tantalum metal-atom encapsulating silicon cage (Ta@Si16) SAs on an organic C60 substrate through deposition, and we characterized their electronic and optical properties by photoelectron spectroscopy and microscopy. The alkaline nature of Ta@Si16 SAs reveals their electronic behaviors, such as charge transfer and electromagnetic near-field sensing, through two-photon photoemission (2PPE) spectroscopy and microscopy with a femtosecond laser. The evolution of the work function for Ta@Si16 SAs on C60, observed by 2PPE spectroscopy, demonstrates charge transfer complexation between the topmost C60 layer and the first Ta@Si16 layer, consistent with the electron-donating alkaline characteristics of Ta@Si16 SAs. Specifically, a small amount of Ta@Si16 SA deposition leads to a dramatic increase in 2PPE intensity, attributable to electromagnetic near-field enhancements, suggesting applications as sensitizers for nonlinear imaging in photoemission microscopy. For the assembled Ta@Si16 SA layers, a plasmonic response of hνp = 17.9 eV is spectroscopically identified, including their valence and conduction band structures, and the plasmonic energetics are discussed in the context of metal doping in bulk silicon.

Efficient and Stable Perovskite/Silicon Tandem Solar Cells Modulated with Triple‐Functional Passivator

AbstractPerovskite/silicon tandem solar cells (TSCs) have aroused much attentions in recent years. One of keys for achieving highly efficient and stable TSCs is to guarantee effective charge transfer, especially on the rough textured silicon substrate due to the poor adhesion between interlayers. Here, a 2‐fluoroisonicotinic acid (2‐FNA) additive that possesses fluorine (‐F), carboxylic acid (‐COOH), and pyridine nitrogen as functional groups in the perovskite precursor to assist the crystallization process is utilized. It shows that 2‐FNA can efficiently reduce the defects and suppress non‐radiative recombination of perovskite layers by bonding with the uncoordinated Pb2+ ions, formamidinium (FA+), and halide vacancies, leading to notably prolonged carrier lifetime. Most importantly, this found that 2‐FNA aids in the formation of better interfacial contact between the perovskite and C60 layer on top, thus enhancing the interfacial electron extraction therein, eventually leading to an increased power conversion efficiency (PCE) of 28.61% on champion perovskite/silicon TSCs from 27.08% on control counterparts. This work provides a practical route to further advance the PV performance and applicability of perovskite/silicon TSCs.

Efficiency-enhancement of lead-free ASnI2Br perovskite solar cells by phenyltrihydrosilane passivation effective for Sn4+ reduction and hydrophobization

The efficiency enhancement of the tin perovskite solar cell consisting of ASnI2Br (ASnI2Br-PVK-PV) is discussed. The ASnI2Br-PVK-PV has a bandgap wider than 1.6 eV and is applicable to the top layer of Pb free perovskite/Si tandem solar cells. The low efficiency of the ASnI2Br-PVK-PV is due to the presence of Sn4+ and defects at the hetero interfaces. We found that PhSiH3 solution treatment (passivation) of the film surface decreases the Sn4+ concentrated on the surface of the perovskite film. At the same time, PhSiH3 treatment (passivation) made the surface of the perovskite layer hydrophobic, resulting in giving better contacts between the perovskite layer and the hydrophobic C60 layer. The efficiency was enhanced from 3.65% to 5.50% after the passivation, proving the effectiveness of the PhSiH3 treatment. The mechanism of the passivation is discussed.

Design, optimization and enhancement of power conversion efficiency exceeding 30% for lead-free all-inorganic double perovskite-based solar cells using dual active layers

Here, we present a comprehensive simulation study focused on the design and optimization of power conversion efficiency (η) for lead-free, all-inorganic double perovskite-based solar cell (DPSC) device using SCAPS 1D. A non-toxic halide double perovskite layer, Cs2AgSb0.25Bi0.75Br6 is employed as absorber layer in designed solar cell along with various electron transport layers like ZnO, TiO2, C60, PCBM, IGZO and hole transport layers including NiO, Cu2O, MoO3, CuI, spiro-OMeTAD in n-i-p heterostructure configuration, aiming to achieve eco-friendly device with optimized efficiency and enhanced stability. The optimal configuration, FTO/C60/ Cs2AgSb0.25Bi0.75Br6/Cu2O/C, achieves a η ∼ 25.32% with Voc ∼ 1.58 V, Jsc ∼ 17.48 mA/cm2 and FF ∼ 91.4%. To further enhance the device performance, double active layers combining CsSnCl3 (band gap ∼ 1.52 eV) and Cs2AgSb0.25Bi0.75Br6 (band gap ∼ 1.80 eV) are introduced into the optimized device to leverage optical absorption for wide range of solar spectrum due to the graded optical band gap. Consequently, the power conversion efficiency of the cell elevated to ∼ 32.23% accompanied by Voc ∼ 1.36 V, Jsc ∼ 26.34 mA/cm2 and FF ∼ 90.3%, with a promise of creating high-efficiency solar cell devices, driving substantial progress in green energy technology.

Modulation of Charge Transport from Two-Dimensional Perovskites to Industrial Charge Transport Layers by the Organic Spacer-Dependent Exciton-Phonon Interactions.

In the past decade, two-dimensional (2D) perovskite surface treatment has emerged as a promising strategy to improve the performance of three-dimensional (3D) perovskite solar cells (PSCs). However, systematic studies on the impact of organic spacers of 2D perovskites on charge transport in 2D/3D PSCs are still lacking. Here, using 2D perovskite film/C60 heterostructures with different organic spacers [butylamine (BA), phenylethylamine (PEA), and 3-fluorophenethylamine (m-F-PEA)], we systematically investigated the carrier diffusion and interfacial transfer process. Using a 2D perovskite film with a thickness of ∼7 nm, we observed subtle differences in electron transfer time between 2D perovskites and C60 layers, which can be attributed to limited thickness and similar electron coupling strength. However, with the thickness of 2D perovskite increasing, electron transfer efficiency in the (BA)2PbI4/C60 heterostructure exhibits the most rapid decrease due to poor carrier diffusion of (BA)2PbI4 caused by stronger exciton-phonon interactions compared to (PEA)2PbI4 and (m-F-PEA)2PbI4 in thickness-dependent charge transfer research. Meanwhile, the fill factor of 2D/3D PSC treated with BAI exhibits the most rapid decrease compared to PEAI- and m-F-PEAI-treated 2D/3D PSCs with the concentration increase of passivators. This study indicates that it is easier to enhance open-circuit voltages and minimize the decrease of fill factor by increasing the concentration of passivators in 2D/3D PSCs when using passivators with a rigid molecular structure.

Effects of the Electrical Properties of SnO2 and C60 on the Carrier Transport Characteristics of p-i-n-Structured Semitransparent Perovskite Solar Cells.

Recently, metal halide perovskite-based top cells have shown significant potential for use in inexpensive and high-performance tandem solar cells. In state-of-the-art p-i-n perovskite/Si tandem devices, atomic-layer-deposited SnO2 has been widely used as a buffer layer in the top cells because it enables conformal, pinhole-free, and highly transparent buffer layer formation. In this work, the effects of various electrical properties of SnO2 and C60 layers on the carrier transport characteristics and the performance of the final devices were investigated using a numerical simulation method, which was established based on real experimental data to increase the validity of the model. It was found that the band alignment at the SnO2/C60 interface does, indeed, have a significant impact on the electron transport. In addition, as a general design rule, it was suggested that at first, the conduction band offset (CBO) between C60 and SnO2 should be chosen so as not to be too negative. However, even in a case in which this CBO condition is not met, we would still have the means to improve the electron transport characteristics by increasing the doping density of at least one of the two layers of C60 and/or SnO2, which would enhance the built-in potential across the perovskite layer and the electron extraction at the C60/SnO2 interface.

Organic Phototransistor with Light-Induced Contact Modulation and Sensitivity Enhancement Using a C60/C70:TAPC Hybrid Channel.

Organic phototransistors (OPTs) are attracting a significant degree of interest as devices that have the potential to play multiple roles, including light sensing, signal amplification, and switching for addressing when they are used for matrix arrays. However, it has been challenging to realize OPTs that can perform all of these roles simultaneously at a sufficient performance level because the channel materials with high carrier mobility often exhibit relatively low photoabsorption. In this work, we propose OPTs with a hybrid bilayer channel consisting of a neat C60 layer and a bulk-heterojunction layer of C70 and 1,1-bis(4-bis(4-methyl-phenyl)-amino-phenyl)-cyclohexane (TAPC) as a possible solution to this issue. While the C60 layer serves as the main carrier-transporting layer with high mobility, the C70:TAPC layer operates as a photoactive layer wherein the photogenerated carriers provide photoinduced contact modulation that leads to a significant enhancement in photosensitivity. With the optimal design maximizing the absorption, the proposed hybrid-channel OPTs show a responsivity of ca. 180 A/W, which is 4.5 times higher than that of the control OPT with a C70:TAPC single channel. The operation mechanism and the origin for the improvement are verified by an in-depth analysis of the photoinduced modulation of the channel and contact resistances of the OPTs.

Extending on-surface synthesis from 2D to 3D by cycloaddition with C60

As an efficient molecular engineering approach, on-surface synthesis (OSS) defines a special opportunity to investigate intermolecular coupling at the sub-molecular level and has delivered many appealing polymers. So far, all OSS is based on the lateral covalent bonding of molecular precursors within a single molecular layer; extending OSS from two to three dimensions is yet to be realized. Herein, we address this challenge by cycloaddition between C60 and an aromatic compound. The C60 layer is assembled on the well-defined molecular network, allowing appropriate molecular orbital hybridization. Upon thermal activation, covalent coupling perpendicular to the surface via [4 + 2] cycloaddition between C60 and the phenyl ring of the molecule is realized; the resultant adduct shows frozen orientation and distinct sub-molecular feature at room temperature and further enables lateral covalent bonding via [2 + 2] cycloaddition. This work unlocks an unconventional route for bottom-up precise synthesis of three-dimensional covalently-bonded organic architectures/devices on surfaces.