Gao Lili, Li Xiaotong, Liu Yan, Fang Junjie, Huang Sheng, Spanopoulos Ioannis, Li Xiaolei, Wang Yao, Chen Lin, Yang Guanjun, Kanatzidis Mercouri G
State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, PR China.
Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States.
ACS Appl Mater Interfaces. 2020 Sep 30;12(39):43885-43891. doi: 10.1021/acsami.0c14925. Epub 2020 Sep 15.
Guanidinium (GA) has been widely used as an additive in solar cells for enhanced performance. However, the size of the guanidinium cation is too large to be incorporated in the cage of the perovskite structure. Instead, GA forms a variety of structures with lead iodide, where its role in the perovskite crystal as well as solar cell devices is unclear. In this study, we demonstrate that GA can be incorporated into the structure of MAPbI as (GA)(MA)PbI. From single-crystal X-ray crystallographic refinement, we observe lattice expansion and Pb-I bond elongation with GA incorporation similar to exerting "negative pressure", which weakens orbital overlap and widens the band gap from 1.49 to 1.53 eV. We find that the highest percentage of GA that can be incorporated into the 3D MAPbI structure is 5.26%, as confirmed by nuclear magnetic resonance. The alloyed (GA)(MA)PbI exhibits increased PL lifetimes from 154.4 to 266.3 ns after GA incorporation while the of (GA)(MA)PbI devices enlarges from 1.05 to 1.11 V. High efficiencies in solar cell devices up to 20.38% with a of 23.55 mA cm, of 1.11 V, and FF of 0.78 have been achieved, with stable photovoltaic performance for 900 h in air.
胍盐（GA）作为一种添加剂已被广泛应用于太阳能电池中以提高其性能。然而，胍盐阳离子的尺寸太大，无法纳入钙钛矿结构的笼状结构中。相反，GA与碘化铅形成了多种结构，其在钙钛矿晶体以及太阳能电池器件中的作用尚不清楚。在本研究中，我们证明GA可以以（GA）（MA）PbI的形式纳入MAPbI的结构中。通过单晶X射线晶体学精修，我们观察到随着GA的掺入，晶格膨胀和Pb-I键伸长，这类似于施加“负压”，削弱了轨道重叠并使带隙从1.49 eV扩大到1.53 eV。我们发现，通过核磁共振证实，能够纳入3D MAPbI结构的GA的最高百分比为5.26%。掺入GA后，合金化的（GA）（MA）PbI的PL寿命从154.4 ns增加到266.3 ns，而（GA）（MA）PbI器件的开路电压从1.05 V扩大到1.11 V。在太阳能电池器件中实现了高达20.38%的高效率，其中短路电流密度为23.55 mA cm，开路电压为1.11 V，填充因子为0.78，并且在空气中具有900小时的稳定光伏性能。
