Improved environmental stability of organic lead trihalide perovskite-based photoactive-layers in the presence of mesoporous TiO2

Abstract

Impressive hybrid photovoltaic device performances have been realised with the methylammonium lead triiodide (MAPbI₃) perovskite absorber in a wide range of device architectures. However, the question as to which of these systems represents the most commercially viable long-term prospect is yet to be answered conclusively. Here, we report on the photoinduced charge transfer processes in MAPbI₃ based films measured under inert and ambient conditions. When exposed to ambient conditions, the coated mesoporous Al₂O₃ and bilayer systems show a rapid and significant degradation in the yield of long-lived charge separation. This process, which does not affect sensitized-mesoporous TiO₂ films, is only found to occur when both light and oxygen are present. These observations indicate that the presence of a mesostructured TiO₂ electron acceptor to rapidly extract the photoexcited electron from the perovskite sensitizer may be crucial for fundamental photovoltaic stability and significantly increases innate tolerance to environmental conditions. This work highlights a significant advantage of retaining mesoscale morphological control in the design of perovskite photovoltaics.