Realizing Efficient Lead-Free Formamidinium Tin Triiodide Perovskite Solar Cells via a Sequential Deposition Route

Zonglong Zhu, Chu-Chen Chueh, Nan Li, Chengyi Mao, Alex K.-Y. Jen*

*Corresponding author for this work

Research output: Journal Publications and ReviewsRGC 21 - Publication in refereed journalpeer-review

224 Citations (Scopus)

Abstract

Recently, the evolved intermediate phase based on iodoplumbate anions that mediates perovskite crystallization has been embodied as the Lewis acid–base adduct formed by metal halides (serve as Lewis acid) and polar aprotic solvents (serve as Lewis base). Based on this principle, it is proposed to constitute efficient Lewis acid–base adduct in the SnI2 deposition step to modulate its volume expansion and fast reaction with methylammonium iodide (MAI)/formamidinium iodide (FAI) (FAI is studied hereafter). Herein, trimethylamine (TMA) is employed as the additional Lewis base in the tin halide solution to form SnY2–TMA complexes (Y = I, F) in the first-step deposition, followed by intercalating with FAI to convert into FASnI. It is shown that TMA can facilitate homogeneous film formation of a SnI2 (+SnF2) layer by effectively forming intermediate SnY2–TMA complexes. Meanwhile, its relatively larger size and weaker affinity with SnI2 than FA+ ions will facilitate the intramolecular exchange with FA+ ions, thereby enabling the formation of dense and compact FASnI3 film with large crystalline domain (>1 µm). As a result, high power conversion efficiencies of 4.34% and 7.09% with decent stability are successfully accomplished in both conventional and inverted perovskite solar cells, respectively. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Original languageEnglish
Article number1703800
JournalAdvanced Materials
Volume30
Issue number6
Online published18 Dec 2017
DOIs
Publication statusPublished - 8 Feb 2018

Funding

This work was supported by the National Science Foundation (DMR-1608279), the Office of Naval Research (N00014-17-1-2260), the Asian Office of Aerospace R&D (FA2386-15-1-4106), and the Department of Energy SunShot program (DE-EE0006710). A.K.-Y.J. thanks the Boeing-Johnson Foundation for financial support.

Research Keywords

  • formamidinium
  • morphology control
  • sequential deposition
  • solar cells
  • tin-based perovskites

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