Interfacial Voids Trigger Carbon-Based, All-Inorganic Cs Pb IBr2 Perovskite Solar Cells with Photovoltage Exceeding 1.33 V

A novel interface design is proposed for carbon-based,all-inorganic CsPbIBr2 perovskite solar cells(PSCs)by introducing interfacial voids between TiO2 electron transport layer and CsPbIBr2 absorber.Compared with the general interfacial engineering strategies,this design exempts any extra modification layer in final PSC.More importantly,the interfacial voids produced by thermal decomposition of 2-phenylethylammonium iodide trigger three beneficial e ects.First,they promote the light scattering in CsPbIBr2 film and thereby boost absorption ability of the resulting CsPbIBr2 PSCs.Second,they suppress recombination of charge carriers and thus reduce dark saturation current density(J0)of the PSCs.Third,interfacial voids enlarge built-in potential(Vbi)of the PSCs,awarding increased driving force for dissociating photo-generated charge carriers.Consequently,the PSC yields the optimized e ciency of 10.20%coupled with an open-circuit voltage(Voc)of 1.338 V.The Voc achieved herein represents the best value among CsPbIBr2 PSCs reported earlier.Meanwhile,the non-encapsulated PSCs exhibit an excellent stability against light,thermal,and humidity stresses,since it remains^97%or^94%of its initial e ciency after being heated at 85℃for 12 h or stored in ambient atmosphere with relative humidity of 30–40%for 60 days,respectively.

Graded Heterojunction Improves Wide-Bandgap Perovskite for Highly Efficient 4-Terminal Perovskite/Silicon Tandem Solar Cells

Wide-bandgap(WBG)perovskite solar cells(PSCs)are essential for highly efficient and stable silicon/perovskite tandem solar cells.In this study,we adopted a synthetic strategy with lead thiocyanate(Pb(SCN)_(2))additive and methylammonium chloride(MACl)posttreatment to enhance the crystallinity and improve the interface of WBG perovskite films with a bandgap of 1.68 eV.The excessive PbI_(2)was formed at grain boundaries and converted into MAPbI_(3-x)Cl_(x)perovskites,which are utilized to form the graded heterojunction(GHJ)and compressive strain.This is beneficial for passivating nonradiative recombination defects,suppressing halide phase segregation,and facilitating carrier extraction.Subsequently,the device with GHJ delivered a champion efficiency of 20.30%and superior stability in ambient air and under 85℃.Finally,we achieved a recorded efficiency of 30.91%for 4-terminal WBG perovskite/TOPCon tandem silicon solar cells.Our findings demonstrate a promising approach for fabricating efficient and stable WBG PSCs through the formation of GHJ.

基于缓慢卤素交换处理CsPbIBr_(2)薄膜制备高性能碳基全无机钙钛矿太阳电池

卤素交换反应为调变卤化物钙钛矿材料的光电学性质提供了一种通用途径.但是,如何降低此类反应的速率,进而抑制缺陷的生长,仍然是一个突出难题.本研究中,我们提出了一种缓慢的卤素交换策略,通过将已制备的CsPbIBr_(2)和CH3NH3PbI3薄膜面对面放置于热台上以进行卤素交换反应,其中Br-和I-各自向CH3NH3PbI3和CsPbIBr_(2)薄膜扩散.实验研究发现通过改变反应参数如温度、时间等,可以精细控制薄膜间的卤素交换速率.例如,较高的温度可以加速卤素交换反应,而较低的温度则可使之减缓或使之完全停止.因此,通过优化卤素交换温度和时间分别为110℃和2 h时,制得了高质量的CsPbI1+xBr_(2)-x薄膜.薄膜的光吸收截止边由590 nm红移至625 nm,有效地拓宽了薄膜的光吸收范围.同时,CsPbI1+xBr_(2)-x薄膜的结晶质量也得到了明显改善,其晶粒尺寸有所增加、结晶性提高、表面粗糙度降低、相分离得到抑制,并且仍然保持原有薄膜优异的湿、热稳定性.因此,基于此类CsPbI1+xBr_(2)-x薄膜制备的碳基全无机钙钛矿太阳电池的效率高达10.94%,远优于基于原始CsPbIBr_(2)薄膜组装的器件(8.21%).另外,制备的高效率电池在85℃氮气环境中加热15小时后,可保持其初始效率的96%;在温、湿度分别为25±3℃和40%±10%的环境中放置45天可保持其初始效率的80%.表明基于缓慢卤素交换策略制备的碳基全无机钙钛矿太阳电池也具有优异的湿、热耐受能力.