P3HT为空穴传输层的碳基钙钛矿太阳电池

碳电极具有成本低、印刷方便、可有效隔离水氧等优点,因此有望利用碳电极材料实现低成本、高稳定性的钙钛矿太阳电池。无空穴传输层的传统碳基钙钛矿太阳电池面临着空穴提取率低、电子逆向传输,钙钛矿和碳电极界面的载流子复合等问题。文章引入聚(3-己基噻吩)(P3HT)作为器件的空穴传输层,使碳基钙钛矿太阳电池ITO/SnO₂/MAPbI₃/P3HT/Carbon的光伏性能得到了显著改善:器件的光电转化效率从11.16% 提高到13.37%。在氮气环境下,连续光照1000h,太阳电池的光电转化效率可保持初始值的87%,而传统器件在光照500h后,其光电转化效率已下降至初始值的60%。     

Simple and Low-Cost Vanadyl Oxalate as Hole Transporting Layer Enables Efficient Organic Solar Cells

Organic solar cells (OSCs) with the conventional configuration usually use polyethylenedioxythiophene:polystyrene sulfonate (PEDOT:PSS) as the hole-transporting layer (HTL); however, its acidity tends to affect the performance and long-term stability of the devices. Therefore, replacing PEDOT:PSS with other more stable HTLs is essential for realizing the practical applications of OSCs. To achieve this goal, a simple and low-cost vanadyl oxalate (VOC₂O₄) is identified as a HTL to facilitate high power conversion efficiencies (PCEs), good stability, and high thickness tolerance to be achieved in OSCs. The VOC₂O₄ thin film can be easily prepared by spin-coating from its aqueous solution onto ITO/glass substrate and thermally annealed at 100 °C to exhibit high transmittance, conductivity, and work function. It can be applied as a robust HTL with wide processing conditions, especially after being heated at 200 °C and treated with UV-ozone (UVO) to afford a very high PCE of 18.94% in OSCs. This value is among the highest PCEs obtained for binary OSCs. In addition, the derived OSCs exhibit high thickness tolerance and better stability than those based on PEDOT:PSS as HTL. These results reveal that VOC₂O₄ is an excellent HTL for OSCs, having great potential for large-area device applications.     

Self‐Assembled Quasi‐3D Nanocomposite: A Novel p‐Type Hole Transport Layer for High Performance Inverted Organic Solar Cells

Hole transport layer (HTL) plays a critical role for achieving high performance solution‐processed optoelectronics including organic electronics. For organic solar cells (OSCs), the inverted structure has been widely adopted to achieve prolonged stability. However, there are limited studies of p‐type effective HTL on top of the organic active layer (hereafter named as top HTL) for inverted OSCs. Currently, p‐type top HTLs are mainly 2D materials, which have an intrinsic vertical conduction limitation and are too thin to function as practical HTL for large area optoelectronic applications. In the present study, a novel self‐assembled quasi‐3D nanocomposite is demonstrated as a p‐type top HTL. Remarkably, the novel HTL achieves ≈15 times enhanced conductivity and ≈16 times extended thickness compared to the 2D counterpart. By applying this novel HTL in inverted OSCs covering fullerene and non‐fullerene systems, device performance is significantly improved. The champion power conversion efficiency reaches 12.13%, which is the highest reported performance of solution processed HTL based inverted OSCs. Furthermore, the stability of OSCs is dramatically enhanced compared with conventional devices. The work contributes to not only evolving the highly stable and large scale OSCs for practical applications but also diversifying the strategies to improve device performance.     

Versatile Self-Assembled Hole Transport Monolayer Enables Facile Processing Organic Solar Cells over 18% Efficiency with Good Generality

Simplifying solution-processing of bulk-heterojunction (BHJ) organic solar cells (OSCs) via efficient interfacial layers with good generality is in great demand for pushing their large-scale applications. In this study, such a novel and cost-effective self-assembled monolayer (SAM) is reported herein as efficient hole transport layer (HTL) for high efficiency OSCs. The SAM-structured 4-(5,9-dibromo-7H-dibenzo[c,g]carbazol-7-yl)butyl)phosphonic acid (DCB-BPA) enables not only enhanced photon harvesting in the active layer but also minimized nonradiative recombination losses to improve interface charge extraction/transport. As a consequence, high short-circuit current (≈28.07 mA cm⁻²) is achieved for PM6:BTP-eC9 based OSCs to deliver a champion power conversion efficiency of 18.16%, among the highest values for OSCs using small organic HTLs to date. Importantly, good generality of this SAMs is demonstrated for representative high-efficiency BHJ OSCs systems like PM6:Y6 and PM6:PC₆₁BM, outperforming conventional poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)-based counterparts. Excitingly, the SAM is applicable for large-area HTL processing via immersion method, affording 16.59% efficiency for PM6:BTP-BO-4Cl based OSCs. This study highlights the great potential of engineered SAMs for facile large-scale fabrication of high performance OSCs.     

Imaging the Electric Potential within Organic Solar Cells

The charge transport in organic solar cells is investigated by surface potential measurements via scanning Kelvin probe microscopy. Access to the solar cell's cross‐section is gained by milling holes with a focused ion beam which enables the direct scan along the charge transport path. In a study of poly(3‐hexylthiophene):1‐(3‐methoxycarbonyl)propyl‐1‐phenyl[6,6]C61 (P3HT:PCBM) bulk heterojunction solar cells, the open circuit voltage is built up at the top contact. A comparison of the potential distribution within normal and inverted solar cells under operation exhibits strongly different behaviors, which can be assigned to a difference in interface properties.     

有机层／阴极界面修饰对体异质结聚合物太阳能电池性能的影响

通过制备四种不同结构的器件,详细分析研究了活性层／阴极界面修饰对P3HT:PCBM聚合物体异质结太阳能电池性能的影响。当在P3HT:PCBM薄膜上旋涂一层PCBM,并蒸镀0.5 nm LiF时所制备的器件的填充因子和光电转换效率都得到较大的提高。对器件的光电性能和薄膜的形貌进行深入分析,阐明界面修饰的作用机理。     

Identifying a Threshold Impurity Level for Organic Solar Cells: Enhanced First‐Order Recombination Via Well‐Defined PC84BM Traps in Organic Bulk Heterojunction Solar Cells

Small amounts of impurity, even one part in one thousand, in polymer bulk heterojunction solar cells can alter the electronic properties of the device, including reducing the open circuit voltage, the short circuit current and the fill factor. Steady state studies show a dramatic increase in the trap‐assisted recombination rate when [6,6]‐phenyl C₈₄ butyric acid methyl ester (PC₈₄BM) is introduced as a trap site in polymer bulk heterojunction solar cells made of a blend of the copolymer poly[N‐9″‐hepta‐decanyl‐2,7‐carbazole‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole) (PCDTBT) and the fullerene derivative [6,6]‐phenyl C₆₁ butyric acid methyl ester (PC₆₀BM). The trap density dependent recombination studied here can be described as a combination of bimolecular and Shockley–Read–Hall recombination; the latter is dramatically enhanced by the addition of the PC₈₄BM traps. This study reveals the importance of impurities in limiting the efficiency of organic solar cell devices and gives insight into the mechanism of the trap‐induced recombination loss.     

Gaining Insight into the Effect of Organic Interface Layer on Suppressing Ion Migration Induced Interfacial Degradation in Perovskite Solar Cells

Ion migration induced interfacial degradation is a detrimental factor for the stability of perovskite solar cells (PSCs) and hence requires special attention to address this issue for the development of efficient PSCs with improved stability. Here, an “S‐shaped, hook‐like” organic small molecule, naphthalene diimide derivative (NDI‐BN), is employed as a cathode interface layer (CIL) to tailor the [6,6]‐phenylC61‐butyric acid methylester (PCBM)/Ag interface in inverted PSCs. By realizing enhanced electron extraction capability via the incorporation of NDI‐BN, a peak power conversion efficiency of 21.32% is achieved. Capacitance–voltage measurements and X‐ray photoelectron spectroscopy analysis confirmed an obvious role of this new organic CIL in successfully blocking ionic diffusion pathways toward the Ag cathode, thereby preventing interfacial degradation and improving device stability. The molecular packing motif of NDI‐BN further unveils its densely packed structure with π–π stacking force which has the ability to effectually hinder ion migration. Furthermore, theoretical calculations reveal that intercalation of decomposed perovskite species into the NDI clusters is considerably more difficult compared with the PCBM counterparts. This substantial contrast between NDI‐BN and PCBM molecules in terms of their structures and packing fashion determines the different tendencies of ion migration and unveils the superior potential of NDI‐BN in curtailing interfacial degradation.     

Mitigating Detrimental Effect of Self-Doping Near the Anode in Highly Efficient Organic Solar Cells

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) has been one of the most established hole transport layers (HTL) in organic solar cells (OSCs) for several decades. However, the presence of PSS⁻ ions is known to deteriorate device performance via a number of mechanisms including diffusion to the HTL-active layer interface and unwanted local chemical reactions. In this study, it is shown that PSS⁻ ions can also result in local p-doping in the high efficiency donor:non-fullerene acceptor blends – resulting in photocurrent loss. To address these issues, a facile and effective approach is reported to improve the OSC performance through a two-component hole transport layer (HTL) consisting of a self-assembled monolayer of 2PACz ([2-(9H-Carbazol-9-yl)ethyl]phosphonic acid) and PEDOT:PSS. The power conversion efficiency (PCE) of 17.1% using devices with PEDOT:PSS HTL improved to 17.7% when the PEDOT:PSS/2PACz two-component HTL is used. The improved performance is attributed to the overlaid 2PACz layer preventing the formation of an intermixed p-doped PSS⁻ ion rich region (≈5–10 nm) at the bulk heterojunction-HTL contact interface, resulting in decreased recombination losses and improved stability. Moreover, the 2PACz monolayer is also found to reduce electrical shunts that ultimately yield improved performance in large area devices with PCE enhanced from 12.3% to 13.3% in 1 cm² cells.     

Conjugated Small Molecule for Efficient Hole Transport in High‐Performance p‐i‐n Type Perovskite Solar Cells

The π‐conjugated organic small molecule 4,4′‐cyclohexylidenebis[N,N‐bis(4‐methylphenyl) benzenamine] (TAPC) has been explored as an efficient hole transport material to replace poly(3,4‐ethylenedio‐xythiophene):poly(styrenesulfonate) (PEDOT:PSS) in the preparation of p‐i‐n type CH₃NH₃PbI₃ perovskite solar cells. Smooth, uniform, and hydrophobic TAPC hole transport layers can be facilely deposited through solution casting without the need for any dopants. The power conversion efficiency of perovskite solar cells shows very weak TAPC layer thickness dependence across the range from 5 to 90 nm. Thermal annealing enables improved hole conductivity and efficient charge transport through an increase in TAPC crystallinity. The perovskite photoactive layer cast onto thermally annealed TAPC displays large grains and low residual PbI₂, leading to a high charge recombination resistance. After optimization, a stabilized power conversion efficiency of 18.80% is achieved with marginal hysteresis, much higher than the value of 12.90% achieved using PEDOT:PSS. The TAPC‐based devices also demonstrate superior stability compared with the PEDOT:PSS‐based devices when stored in ambient circumstances, with a relatively high humidity ranging from 50 to 85%.     

Accurate Measurement and Characterization of Organic Solar Cells

Methods to accurately measure the current–voltage characteristics of organic solar cells under standard reporting conditions are presented. Four types of organic test cells and two types of silicon reference cells (unfiltered and with a KG5 color filter) are selected to calculate spectral‐mismatch factors for different test‐cell/reference‐cell combinations. The test devices include both polymer/fullerene‐based bulk‐heterojunction solar cells and small‐molecule‐based heterojunction solar cells. The spectral responsivities of test cells are measured as per American Society for Testing and Materials Standard E1021, and their dependence on light‐bias intensity is reported. The current–voltage curves are measured under 100 mW cm^–2 standard AM 1.5 G (AM: air mass) spectrum (International Electrotechnical Commission 69094‐1) generated from a source set with a reference cell and corrected for spectral error.     

Organic Ionic Plastic Crystals as Hole Transporting Layer for Stable and Efficient Perovskite Solar Cells

Organic ionic plastic crystals (OIPCs) are synthesized through a simple metal‐free, cost‐effective approach. The strategized synchronization of electron‐rich phenoxazine with benzimidazolium iodide (OIPC‐I) and bromide (OIPC‐Br) salts lead to enhanced hole mobility and conductivity of OIPCs which is suitable for an efficient alternative to conventional organic hole transporting materials (HTMs) for stable perovskite solar cells (PSCs). The fabricated PSCs with OIPC‐I as hole transporting layer yielded a power conversion efficiency of 15.0% and 18.1% without and with additive (Li salt) respectively, which are comparable with spiro‐OMeTAD based devices prepared under similar conditions. Furthermore, the PSCs with OIPCs show good stability compared to the spiro‐OMeTAD with or without additives. Here, first time benzimidazolium‐based OIPCs have been used as an alternative organic HTM for perovskite solar cells, which opens a window for the design of effective OIPCs for highly efficient PSCs with long‐term stability.     

A Universal Method to Enhance Flexibility and Stability of Organic Solar Cells by Constructing Insulating Matrices in Active Layers

With the rapid development of power conversion efficiency (PCE), flexibility–stability of organic solar cells (OSCs) are becoming one of the primary barriers for commercialization. This work shows that insulating poly(aryl ether) (PAE) resins have highly twisted‐stiff backbones without any side chains, which possess excellent mechanical stability, thermal stability, and good compatibility with organic photovoltaic materials. After introducing 5 wt% PAE resin as supporting matrices into the bulk heterojunction (BHJ) layer, the device yields a high PCE of 16.13%. Importantly, the devices show impressive flexibility and improved stability with passivated morphology, such as PM6/Y6‐based devices with 30 wt% PAE retains the PCE of 15.17% and exhibits enhanced 4.4‐fold elongation at break (25.07%). This is the recorded stretchability of the BHJ layer for OSCs with PCE > 8%, and morphological changes during tensile deformation are first investigated by in situ wide‐angle X‐ray scattering measurements. The PAE matrices strategy exhibits good universality in the other four photovoltaic systems. These results demonstrate that heat‐resistant PAE resins serve as supporting matrices with a tunneling effect into OSCs without sacrificing photovoltaic performance and simultaneously improve the flexibility and stability of devices, which can play an important role in promoting the development of stable and wearable electronics.     

空穴传输层厚度对有机发光二极管性能的影响

采用聚乙烯基咔唑(PVK)作为空穴传输层,8-羟基喹啉铝(Alq3)作为发光层,制备了结构为ITO/PVK/Alq3/Mg∶Ag/Al的有机发光二极管(OLED),通过测试器件的电流-电压-发光亮度特性,研究了空穴传输层厚度对OLED器件性能的影响,优化了器件功能层的厚度匹配.实验结果表明,OLED的光电性能与空穴传输层的厚度密切相关,空穴传输层厚度为15nm时,OLED器件具有最低的启亮电压,最高的发光亮度和最大的发光效率.     

Determining the Dielectric Constants of Organic Photovoltaic Materials Using Impedance Spectroscopy

The photovoltaic and electrical properties of organic semiconductors are characterized by their low dielectric constant, which leads to the formation of polarons and Frenkel excitons. The low dielectric constant of organic semiconductors has been suggested to be significantly influential in geminate and bimolecular recombination losses in organic photovoltaics (OPVs). However, despite the critical attention that the dielectric constant has received in literature discussions, there has not yet been a thorough study of the dielectric constant in common organic semiconductors and how it changes when blended. In fact, there have been some inconsistent and contradictory reports on such dielectric constants, making it difficult to identify trends. Herein, at first a detailed explanation of a specific methodology to determine the dielectric constant in OPV materials with impedance spectroscopy is provided, including guidelines for possible experimental pitfalls. Using this methodology, the analysis for the dielectric constant of 17 common neat organic semiconductors is carried out. Furthermore, the relationship between the dielectric constant and blend morphology are studied and determined. It is found that the dielectric constant of a blend system can be very accurately predicted solely based on the dielectric constants of the neat materials, scaled by their respective weight ratios in the blend film.     

有机薄膜太阳电池的研究进展

有机薄膜太阳电池作为一种新型光伏电池,近年来得到了迅猛发展。其制备工艺简单、价格低廉、柔性、质轻,为人类解决能源问题提供了一种崭新的途径。文章综述了近年来有机薄膜太阳电池的发展状况,结合有机薄膜太阳电池的发展历史,分析了单异质结、体异质结和叠层三种典型结构器件的工作原理和研究成果,探讨了各种器件结构的优缺点,并对有机薄膜太阳电池的发展趋势作了展望。     

Tuning Hole Transport Layer Using Urea for High‐Performance Perovskite Solar Cells

Interface engineering is critical to the development of highly efficient perovskite solar cells. Here, urea treatment of hole transport layer (e.g., poly(3,4‐ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS)) is reported to effectively tune its morphology, conductivity, and work function for improving the efficiency and stability of inverted MAPbI₃ perovskite solar cells (PSCs). This treatment has significantly increased MAPbI₃ photovoltaic performance to 18.8% for the urea treated PEDOT:PSS PSCs from 14.4% for pristine PEDOT:PSS devices. The use of urea controls phase separation between PEDOT and PSS segments, leading to the formation of a unique fiber‐shaped PEDOT:PSS film morphology with well‐organized charge transport pathways for improved conductivity from 0.2 S cm^?1 for pristine PEDOT:PSS to 12.75 S cm^?1 for 5 wt% urea treated PEDOT:PSS. The urea‐treatment also addresses a general challenge associated with the acidic nature of PEDOT:PSS, leading to a much improved ambient stability of PSCs. In addition, the device hysteresis is significantly minimized by optimizing the urea content in the treatment.     

Multifunctional Synthesis Approach of In:CuCrO2 Nanoparticles for Hole Transport Layer in High‐Performance Perovskite Solar Cells

While there are very limited studies of doped ternary metal oxide based hole transport materials, a multifunctional synthesis approach of In doped CuCrO₂ nanoparticles (NPs) as efficient hole transport layers (HTLs) including simplifying the synthesis requirements is proposed, enabling doping and achievement of treatment‐free HTLs. Remarkably, compared with conventional methods for synthesizing CuCrO₂ NPs, the newly proposed azeotropic promoted approach dramatically reduces the reaction time by 90% and the calcination temperature by one‐third, which not only promotes high throughput production but also reduces power consumption and cost in synthesis. Equally important, indium is successfully doped into CuCrO₂, which is fundamentally difficult in low temperature processes. The In doping offers less d–d transition of Cr³⁺ and p‐type doping characteristics for improving HTL transmittance and conductivity, respectively. Interestingly, In doped CuCrO₂ HTL with these improvements can be achieved by a simple ambient‐condition process and exhibits thermal stability up to 200 °C, which allows perovskite solar cells (PSCs) to achieve a power conversion efficiency of 20.54%. Meanwhile, the devices show good repeatability and photostability. Consequently, the work contributes to establishing a simple approach to realize pristine and doped multinary oxides based HTL for the development of practical and high performing PSCs.     

Copper (I) Selenocyanate (CuSeCN) as a Novel Hole‐Transport Layer for Transistors,Organic Solar Cells,and Light‐Emitting Diodes

The synthesis and characterization of copper (I) selenocyanate (CuSeCN) and its application as a solution‐processable hole‐transport layer (HTL) material in transistors, organic light‐emitting diodes, and solar cells are reported. Density‐functional theory calculations combined with X‐ray photoelectron spectroscopy are used to elucidate the electronic band structure, density of states, and microstructure of CuSeCN. Solution‐processed layers are found to be nanocrystalline and optically transparent (>94%), due to the large bandgap of ≥3.1 eV, with a valence band maximum located at ?5.1 eV. Hole‐transport analysis performed using field‐effect measurements confirms the p‐type character of CuSeCN yielding a hole mobility of 0.002 cm² V^?1 s^?1. When CuSeCN is incorporated as the HTL material in organic light‐emitting diodes and organic solar cells, the resulting devices exhibit comparable or improved performance to control devices based on commercially available poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate as the HTL. This is the first report on the semiconducting character of CuSeCN and it highlights the tremendous potential for further developments in the area of metal pseudohalides.