Cross-linkable fluorene-based hole transporting materials for perovskite solar cells

Cross-linkable hole transporting materials (HTMs) based on fluorene core containing vinyl groups were synthesized and analyzed. It has been demonstrated that these HTMs are cross-linkable at temperatures above 200 °C and they are thermally stable at up to 400 °C. Cross-linking has little effect on energy level (HOMO) and causes only slight changes in the hole drift mobility values at room temperature, due to changes in spatial and energetic disorder. While employing cross-linked fluorene-diphenylamine derivative (V1145) as an HTM layer between perovskite and indium-tin oxide (ITO) in inverted perovskite solar cells (PSCs), the power conversion efficiency (PCE) of the cell was 11.42% (under AM 1.5G 100 mW cm−2 illumination), demonstrating the potential of the presented class of dopant-free organic HTMs.