Improving the Stability of Ambient Processed, SnO<sub>2</sub>‐Based, Perovskite Solar Cells by the UV‐Treatment of Sub‐Cells
Gayathri Mathiazhagan, Aaron Seeber, Thomas R. Gengenbach, Simone Mastroianni, Doojin Vak, Anthony S. R. Chesman, Mei Gao, Dechan Angmo, Andreas Hinsch
Abstract
SnO 2 is nowadays the widely preferred material as an electron transport layer (ETL) in most n‐i‐p planar perovskite solar cells (PSCs) due to its facility for ambient, low temperature processing, and ultraviolet (UV) stability. Most reports published so far study device stability on full cells. Herein, the role of slot‐die‐coated SnO 2 on air‐processed planar PSCs by analyzing sub‐cells (indium tin oxide [ITO]/SnO 2 /perovskite) under UV exposure is investigated. Results from UV–vis spectroscopy, depth profiling using X‐ray diffraction measurement in grazing incidence mode (GIXRD), X‐ray photoelectron spectroscopy (XPS), and photoluminescence spectroscopy measurements show that UV treatment of ITO/SnO 2 /perovskite leads to a reduced electron transfer to the SnO 2 layer and a gradual increase in the amount of PbI 2 toward the perovskite surfaces. Subsequently, hole transport layer (HTL) and electrodes are applied on SnO 2 /perovskite interfaces (UV‐treated and non‐UV‐treated) and complete devices are fabricated. Device performance is compared and analyzed through J – V curves and maximum power point (MPP) tracking. Results show that devices built on a UV‐treated SnO 2 /perovskite interface show better stability attributed to the presence of excess PbI 2 resulting in a passivation effect. Challenges in uniform film formation of slot‐die‐coated SnO 2 and potential solutions using a polymeric additive are also highlighted.