Anchoring Charge Selective Self-Assembled Monolayers for Tin-Lead Perovskite Solar Cells.

Self-assembled monolayers (SAMs) have displayed great potential for improving efficiency and stability in p-i-n perovskite solar cells. The anchoring of SAMs at the conduction metal oxide substrates and their interaction with perovskite materials must be rationally tailored to ensure efficient charge carrier extraction and improved quality of the perovskite films. Herein, we selected SAM molecules with different anchoring groups and spacers to control the interaction with perovskite in the p-i-n mixed Sn-Pb perovskite solar cells. We found that the monolayer with the carboxylate group exhibits appropriate interaction and has a more favourable orientation and arrangement than that of the phosphate group. This resulted in reduced non-radiative recombination and enhanced crystallinity. In addition, the short chain length led to an improved energy level alignment of SAMs with perovskite, improving hole extraction. As a result, the narrow bandgap (∼1.25 eV) Sn-Pb perovskite solar cell devices showed efficiencies of up to 23.1% with an open circuit voltage of up to 0.89 V. Unencapsulated devices retained 93% of their initial efficiency after storage in N 2 atmosphere for over 2500 hours. Overall, this work highlights the underexplored potential of SAMs for perovskite photovoltaics and provides essential findings on the influence of their structural modification. This article is protected by copyright. All rights reserved.