Interfacial Engineering with a Hole-Selective Self-Assembled Monolayer for Tin Perovskite Solar Cells via a Two-Step Fabrication

This work is the first report on a hole-selective tin-based perovskite solar cell (PSC) using the concept of a self-assembled monolayer (SAM) to modify the ITO surface to fabricate a uniform tin perovskite layer via a two-step sequential deposition method. Herein, we developed a preheating procedure to diminish effectively the amounts of hydroxyl groups and oxygen vacancies on the ITO surface to produce a uniform SAM. The ITO substrate preheated at 400 °C gave the best device performance for an efficiency of power conversion (PCE) reaching 6.5%, and 80% of the initial PCE was maintained in a glovebox for ∼1900 h. Electrochemical impedance spectra and time-resolved spectra were used to understand the interfacial charge recombination and hole-extraction kinetics in relation to the observed device performance. The present work thus provides a new direction for the development of SAM-based lead-free perovskite solar cells for their future scaled-up production.