Surface-Orientation Elimination of Vapor-Deposited PbI2 Flakes for Efficient Perovskite Synthesis on Curved Solar Cells

Ziyi Li; Jinzhao Li; Huanqi Cao; Yicheng Qian; Jianyong Zhai; Yuan Qiu; Liying Yang; Shougen Yin

doi:10.1021/acsami.1c12283

Surface-Orientation Elimination of Vapor-Deposited PbI₂ Flakes for Efficient Perovskite Synthesis on Curved Solar Cells

ACS Appl Mater Interfaces. 2021 Sep 29;13(38):45496-45504. doi: 10.1021/acsami.1c12283. Epub 2021 Sep 14.

Authors

Ziyi Li¹, Jinzhao Li², Huanqi Cao¹, Yicheng Qian¹, Jianyong Zhai¹, Yuan Qiu¹, Liying Yang¹, Shougen Yin¹

Affiliations

¹ Key Laboratory of Display Materials and Photoelectric Devices (Ministry of Education), Tianjin Key Laboratory for Photoelectric Materials and Devices, School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384, P. R. China.
² HySPRINT Innovation Lab: Young Investigator Group Hybrid Materials Formation and Scaling, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin 12489, Germany.

PMID: 34521200
DOI: 10.1021/acsami.1c12283

Abstract

Vapor deposition of perovskite solar cells (PSCs) has attracted considerable interest for its dry processing characteristics. However, a two-step sequential vapor deposition method suffers from ineffective conversion of PbI₂ to perovskite with reasons still unclear. In this report, we carefully investigated the crystallization orientation of PbI₂ films deposited by physical vapor deposition via synchrotron grazing-incidence wide-angle X-ray scattering (GIWAXS) and observed an asymmetric scattering pattern with respect to the q_z-axis. The observed oriented morphology and texture hinder the diffusion of MAI molecules in the PbI₂ films synthesized by vapor deposition, resulting in over 15% PbI₂ remaining at the buried interface after reaction with MAI vapor. As a result, the MAPbI₃ synthesized in this way was also highly oriented, especially in the surface layers. Surface fumigation (SF) step was introduced to decrease the orientational anisotropy of PbI₂, which successfully breaks the diffusion barriers of MAI molecules by forming a complex layer on the PbI₂ surface with polar solvent vapors, like dimethyl sulfoxide or 1,3-dimethyl-2-imidazolidinone. We infer that the SF treatment changes the vapor-solid reaction mechanism from reaction-crystallization to dissolution-recrystallization, which largely promotes the conversion of PbI₂ to perovskite. Defects were reduced in perovskite synthesized in this way, and a p-i-n device with 19.56% efficiency was fabricated, which is among the highest efficiencies reported for sequential-vapor-deposited PSCs. Notably, this method enables the fabrication of conformal perovskite layers on uneven substrates. An exemplary PSC showing efficiency of 8.93% was fabricated on a precurved substrate. We believe that the method is applicable to the fabrication of tandem or curved PSCs that are compatible with wearable or building/autocar-integrated photovoltaics in the future.

Keywords: conformal coverage; curved perovskite solar cell; surface fumigation; tandem solar cell; vapor−solid reaction.