In-situ gas cell heating of FAPbI3 (FA-based perovskite) in argon leads to the formation (T<175˚C) and then segregation (T> 175˚C) of Pb precipitates at the grain boundaries (bright contrast). Upon optimization of synthesis procedures (e.g. stable T of 175˚C), device efficiencies of up to 17.09% obtained.
Left: Sequential atomic contrast STEM images accompanied by normalized histograms showing the evolution of grain interiors (blue curve) and multiple grain boundaries (red curve).
Reference: Jeffery A. Aguiar, Sarah Wozny, Terry G. Holesinger, Toshihiro Aoki, Maulik K. Patel, Mengjin Yang, Joseph J. Berry, Mowafak Al-Jassim, Weilie Zhou and Kai Zhu. “In situ investigation of the formation and metastability of formamidinium lead tri-iodide perovskite solar cells,” Energy & Environmental Science (2016) . Abstract
Image Copyright © The Royal Society of Chemistry 2016.