Phenothiazine-Based Hole-Transporting Materials toward Eco-friendly Perovskite Solar Cells

Abstract

Organic hole-transporting materials (HTMs), AZO-I and AZO-II, were synthesized via Schiff base chemistry by functionalizing a phenothiazine core with triarylamine(s) through azomethine bridges. Substantial enhancements in the power conversion efficiency (PCE = 12.6% and 14% for AZO-I and AZO-II, respectively) and stability (68% or 91% of PCE retained after 60 days for AZO-I or AZO-II, respectively) of perovskite solar cells (PSCs) were achieved when switching from mono- (AZO-I) to disubstituted (AZO-II) HTMs. The extremely low production costs (9 and 12 $/g for AZO-I and AZO-II, respectively), together with the Pd-catalyst-free synthesis, make these materials excellent candidates for low-cost and eco-friendly PSCs.