Zhao Jiashang, Caselli Valentina M, Bus Marcel, Boshuizen Bart, Savenije Tom J
Department of Chemical Engineering, Delft University of Technology, 2629 HZ Delft, The Netherlands.
ACS Appl Mater Interfaces. 2021 Apr 14;13(14):16309-16316. doi: 10.1021/acsami.1c00714. Epub 2021 Mar 31.
Wide-band-gap perovskites such as methylammonium lead bromide (MAPB) are promising materials for tandem solar cells because of their potentially high open-circuit voltage, which is yet still far below the maximum limit. The relatively short charge-carrier lifetimes deduced from time-resolved photoluminescence (TRPL) measurements seem in strong contrast with the long lifetimes observed with time-resolved photoconductance measurements. This is explained by a large amount of hole defect states, > 10 cm, in spin-coated layers of MAPB residing at or near the grain boundaries. The introduction of hypophosphorous acid (HPA) increases the average grain size by a factor of 3 and reduces the total concentration of the trap states by a factor of 10. The introduction of HPA also increases the fraction of initially generated holes that undergo charge transfer to the selective contact, Spiro-OMeTAD (SO), by an order of magnitude. In contrast to methylammonium lead iodide (MAPI)/SO bilayers, a reduction of the carrier lifetime is observed in MAPB/SO bilayers, which is attributed to the fact that injected holes undergo interfacial recombination via these trap states. Our findings provide valuable insight into the optoelectronic properties of bromide-containing lead halide perovskites essential for designing efficient tandem solar cells.
诸如甲基溴化铅（MAPB）之类的宽带隙钙钛矿因其潜在的高开路电压而成为串联太阳能电池的有前景的材料，不过该开路电压仍远低于最大极限。从时间分辨光致发光（TRPL）测量得出的相对较短的电荷载流子寿命似乎与时间分辨光电导测量所观察到的长寿命形成强烈对比。这可以通过存在于MAPB旋涂层中晶界处或附近的大量空穴缺陷态（>10 cm）来解释。次磷酸（HPA）的引入使平均晶粒尺寸增大了3倍，并使陷阱态的总浓度降低了10倍。HPA的引入还使最初产生的经历电荷转移至选择性接触材料Spiro-OMeTAD（SO）的空穴比例增加了一个数量级。与甲基碘化铅（MAPI）/SO双层结构相反，在MAPB/SO双层结构中观察到载流子寿命缩短，这归因于注入的空穴通过这些陷阱态发生界面复合。我们的研究结果为设计高效串联太阳能电池所必需的含溴化铅卤化物钙钛矿的光电特性提供了有价值的见解。
