In-depth study of degradation in scalable wide bandgap perovskite cells

Abstract

Perovskite solar cells with a wide bandgap (WBG) perovskite absorber of 1.68 eV are fabricated and their performance evolution under accelerated stressing conditions are compared with 1.61 eV reference devices. The cells are processed entirely with scalable deposition methods, to guarantee their relevance for industrial application. Different stress tests, following the International Summit on Organic Photovoltaic Stability (ISOS) protocols, are performed, namely prolonged exposure to light (ISOS-L1), heat (ISOS-D2) and a combination of these (ISOS-L2). First, the ISOS-L1 test highlights the excellent stability of the chosen WBG composition, with minimal degradation after 60 h. Secondly, the ISOS-D2 test led to a more significant degradation of the WBG cells, with only 80% efficiency retained after 95 h. The main cause of degradation was found to be interface-related, specifically the formation of a charge transport barrier at the perovskite/electron transport layer interface, while the perovskite absorption properties remained unaffected by the stress test. Finally, the ISOS-L2 test led to an even faster degradation, with only 80% efficiency retained after 35 h. There, the perovskite absorber itself was found to be significantly degraded due to the combined action of light and heat. Altogether, this study highlights the main degradation pathways in WBG perovskite cells while showing the importance of diversified and combined stresses in evaluating their stability.