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Stability of perovskite films: a comparison between 2D-stabilized and rubidium-based perovskites studied by imaging and spectroscopic techniques

Grant number: 19/17170-2
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): December 01, 2019
Effective date (End): April 30, 2021
Field of knowledge:Physical Sciences and Mathematics - Chemistry
Principal Investigator:Ana Flávia Nogueira
Grantee:Eduardo Giangrossi Machado
Home Institution: Instituto de Química (IQ). Universidade Estadual de Campinas (UNICAMP). Campinas , SP, Brazil
Associated research grant:17/11986-5 - Research Division 1 - dense energy carriers, AP.PCPE

Abstract

The Photoconversion Efficiency (PCE) of solar cells containing hybrid perovskites, using organic cations such as formamidinium and cesium, has approached the 25.6% mark, reaching an important milestone of being close to the commercially available silicon cell. However, the stability of these devices is still not suited for commercial application as they still present degradation facing environmental conditions, which elevates the cost of using such technology. This project proposes a physicochemical investigation of the degradation mechanisms by means of imaging and spectroscopic techniques. The goal is to achieve a comprehension of how those films decompose and possibly to propose alternatives to increase their stability. More specifically, pure phase 2D-stabilized FAxCs1-xPb(IyBr1-y)3 and a multication rubidium incorporated RbaCsbFA(1-a-b)PbI3 will be tested as they are considered frontier perovskites regarding their PCE and their chemical stability. To gain insight into the mechanisms ruling this unwanted process, the Ellipso-Microscopy for Surface Imaging (EMSI) will be employed as it allows an in situ monitoring of the surface, while changing the desired parameters. From this technique, changes in the refractive index can be related to changes in composition while the spatial resolution will allow the determination of specific sites where the degradation would be taking place. In order to make a macro/microscopic correspondence, other characterization techniques will be employed such as in situ X-ray diffraction, in situ scanning electron microscopy, synchrotron nano-FTIR and photophysics characterization of the material comparing the response before and after the exposition to changes in temperature, humidity and light. It is expected from this project to deepen our understanding of the mechanisms and processes by which the most stable perovskites decompose, facing environmental conditions, aiming at proposing an alternative to increase their stability. (AU)