Armaroli Giovanni, Maserati Lorenzo, Ciavatti Andrea, Vecchi Pierpaolo, Piccioni Alberto, Foschi Martina, Van der Meer Valentina, Cortese Chiara, Feldman Matias, Foderà Vito, Lemercier Thibault, Zaccaro Julien, Guillén Javier Mayén, Gros-Daillon Eric, Fraboni Beatrice, Cavalcoli Daniela
Department of Physics and Astronomy, University of Bologna, 40127 Bologna, Italy.
University Grenoble Alpes, CNRS, Grenoble INP, Institut Néel, F38042 Grenoble, France.
ACS Energy Lett. 2023 Sep 26;8(10):4371-4379. doi: 10.1021/acsenergylett.3c01429. eCollection 2023 Oct 13.
Metal halide perovskites (MHPs) are disruptive materials for a vast class of optoelectronic devices. The presence of electronic trap states has been a tough challenge in terms of characterization and thus mitigation. Many attempts based on electronic spectroscopies have been tested, but due to the mixed electronic-ionic nature of MHP conductivity, many experimental results retain a large ambiguity in resolving electronic and ionic charge contributions. Here we adapt a method, previously used in highly resistive inorganic semiconductors, called photoinduced current transient spectroscopy (PICTS) on lead bromide 2D-like ((PEA)PbBr) and standard "3D" (MAPbBr) MHP single crystals. We present two conceptually different outcomes of the PICTS measurements, distinguishing the different electronic and ionic contributions to the photocurrents based on the different ion drift of the two materials. Our experiments unveil deep level trap states on the 2D, "ion-frozen" (PEA)PbBr and set new boundaries for the applicability of PICTS on 3D MHPs.
金属卤化物钙钛矿（MHPs）是一类对众多光电器件具有颠覆性的材料。电子陷阱态的存在在表征以及缓解方面一直是一个严峻的挑战。基于电子光谱学的许多尝试都已进行测试，但由于MHP导电性的电子 - 离子混合性质，许多实验结果在分辨电子和离子电荷贡献方面仍存在很大的模糊性。在此，我们采用一种先前用于高电阻无机半导体的方法，即对类二维溴化铅（(PEA)PbBr）和标准“三维”（MAPbBr）MHP单晶进行光致电流瞬态光谱（PICTS）。我们展示了PICTS测量的两个概念上不同的结果，基于两种材料不同的离子漂移区分了对光电流的不同电子和离子贡献。我们的实验揭示了二维“离子冻结”（PEA）PbBr上的深能级陷阱态，并为PICTS在三维MHPs上的适用性设定了新的界限。
