Molybdenum cluster iodides for improved CsPbBr3 perovskite photoelectrodes: a superatomic approach to stability, passivation, and optoelectronic performance.

Abstract

Lead halide perovskite solar cells, despite their outstanding optoelectronic properties, suffer from poor long-term stability under environmental stressors, limiting their industrial scalability. To address this issue, we explored photoelectrodes composed of FTO/TiO2 substrates coated with hybrid heterostructures. The latter combine ligated molybdenum clusters (MCs), [{Mo6Ii8}La6] (Ii = face-capping iodine; La = terminal iodine or H2O), integrated with CsPbBr3 (CPB). Two strategies were explored: (i) one-step spin-coating to form MC@CPB composites and (ii) two-step electrophoretic deposition (EPD) to create large CPB/MCEPD interfaces by overlaying MCs onto a predeposited CPB film. Photoelectrochemical analysis showed that MC-integrated photoelectrodes exhibit (i) extended absorption, (ii) enhanced chemical stability, and (iii) improved photocurrent stability compared to pristine CPB. The MCs act as passivation agents, limiting surface reactivity and halide migration. DFT calculations were used to model the MC/CPB interfaces, revealing mechanistic insights into the observed performance enhancements such as a strong anchoring of MCs via Mo-I-Pb bonds and a bandgap mainly governed by the MC contribution. This combined experimental and computational study demonstrates that MC integration offers a robust strategy to enhance both the stability and the performance of perovskite solar cells.