Current advancements on charge selective contact interfacial layers and electrodes in flexible hybrid perovskite photovoltaics

Perovskite-based photovoltaic materials have been attracting attention for their strikingly improved performance at converting sunlight into electricity.The beneficial and unique optoelectronic characteristics of perovskite structures enable researchers to achieve an incredibly remarkable power conversion efficiency.Flexible hybrid perovskite photovoltaics promise emerging applications in a myriad of optoelectronic and wearable/portable device applications owing to their inherent intriguing physicochemical and photophysical properties which enabled researchers to take forward advanced research in this growing field.Flexible perovskite photovoltaics have attracted significant attention owing to their fascinating material properties with combined merits of high efficiency,light-weight,flexibility,semitransparency,compatibility towards roll-to-roll printing,and large-area mass-scale production.Flexible perovskite-based solar cells comprise of 4 key components that include a flexible substrate,semi-transparent bottom contact electrode,perovskite(light absorber layer)and charge transport(electron/hole)layers and top(usually metal)electrode.Among these components,interfacial layers and contact electrodes play a pivotal role in influencing the overall photovoltaic performance.In this comprehensive review article,we focus on the current developments and latest progress achieved in perovskite photovoltaics concerning the charge selective transport layers/electrodes toward the fabrication of highly stable,efficient flexible devices.As a concluding remark,we briefly summarize the highlights of the review article and make recommendations for future outlook and investigation with perspectives on the perovskite-based optoelectronic functional devices that can be potentially utilized in smart wearable and portable devices.

Influence of charge transport layer on the crystallinity and charge extraction of pure tin-based halide perovskite film

As one of the most compelling photovoltaic devices, halide perovskite (PVK) solar cells have achieved a new surprising record power conversion efficiency (PCE) of 25.8%in 2021 [1]. This demonstrates the great potential of halide PVK solar cells as a highly competitive substitute to replace silicon-based solar cells in the photovoltaic market [2–6].

Recent advances in Pb-Sn mixed perovskite solar cells

Organic-inorganic hybrid lead-tin perovskite solar cells(Pb-Sn PSCs)have attracted much attention because of their advantages of low toxicity,variable bandgap,and feasibility for all-perovskite tandem solar cells,and the current power conversion efficiency(PCE)has exceeded 23%.However,due to the rambunctious crystallization process,easily oxidized Sn(Ⅱ)and inadequate energy level arrangement,there are many defects in perovskite films resulting in serious carrier recombination,which makes PCE still lag Pb-based PSCs.The quality of perovskite films is an important factor affecting the overall device performance.The selection and optimization of transport layers not only determines the interface energy level arrangement but also affects the carrier transport.In this paper,the research progress in improving performance of Pb-Sn PSCs in recent years is reviewed from aspects of perovskite layer and transport layers.The profound understanding of different promotion methods is summarized as well.These results have certain guiding significance for the future development and commercial application of Pb-Sn PSCs.

Recent advances of interface engineering in inverted perovskite solar cells

Perovskite solar cells(PSCs)have witnessed great achievement in the past decade.Most of previous researches focus on the n-i-p structure of PSCs with ultra-high efficiency.While the n-i-p devices usually used the unstable charge transport layers,such as the hygroscopic doped spiro-OMe TAD,which affect the long-term stability.The inverted device with the p-i-n structure owns better stability when using stable undoped organic molecular or metal oxide materials.There are significant progresses in inverted PSCs,most of them related to charge transport or interface engineering.In this review,we will mainly summarize the inverted PSCs progresses related to the interface engineering.After that,we prospect the future direction on inverted PSCs.

Simplified Compact Perovskite Solar Cells with Efficiency of 19.6% via Interface Engineering

For the commercialization of perovskite solar cells(PSCs), it is more appealing to develop high-performance simplified PSCs where perovskite films are just sandwiched between the back and front electrodes, in order to simplify the fabrication process and to reduce the cost. However, to date, this kind of devices shows rather low performance, and there are few researches on this subject.Herein, we report on a kind of compact PSCs(CPSCs) that are free of independent charge transport layers(CTLs). The devices are realized by the use of organic monolayer-modified effective electrodes, along with the use of [6,6]-phenyl-C61-butyric acid methyl ester(PCBM)-assisted anti-solvent technique to obtain ultra-thin(~10 nm) PCBM-embedded perovskite films. Compared to control devices, CPSCs achieve a promising champion power conversion efficiency of 19.6% with largely reduced hysteresis. Moreover, the unencapsulated CPSC shows good stability under ambient atmosphere, with only 10% efficiency loss after 60 days’ storage. This work indicates that, by delicate design, CPSCs with smaller materials consumption in device architecture can perform competitively as conventional PSCs. Further reduction in the actual usage of costly CTL materials can be expected upon our CPSCs by developing more facile and economic methods to prepare ultra-thin CTLs.

基于氯化物处理的钙钛矿自供电无电荷传输层光电探测器用于弱光检测

有机-无机卤化物钙钛矿因其可溶液加工和优异的光电特性而在光电探测器(PD)中得到了广泛应用.然而,基于钙钛矿的PD一般需要电荷传输层提供足够的分离和传输驱动力,这会增加钙钛矿PD的材料成本.本研究通过溶液法制备了基于苯基三甲基氯化铵(PTACl)处理的无电荷传输层钙钛矿自供电PD.以(CsFAMA)Pb(BrI)3作为光活性层,这种三元阳离子混合卤化物钙钛矿沉积后的垂直分布差异为电荷分离和传输提供了驱动力,PTACl处理能加强电荷分离和运输.这种PD在自供电模式下表现出优异的光电探测性能,其中光暗电流比为1.8×10^(5),响应度为198 mA W^(−1),探测率为1.48×10^(13)/1.24×10^(11) Jones(暗/噪声电流法计算).没有封装的PD在700 h的测试中也表现出良好的空气稳定性,且该PD对0.64 nW cm^(−2)的弱光仍有明显的响应,PD阵列也验证了这种弱光检测能力.本工作制备的钙钛矿自供电PD为弱光检测的发展提供了一种简单可行的途径.