Multi-arm and Substituent Effects on Charge Transport of Organic Hole Transport Materials

We explore several potential dopant-free triphenylamine-based HTMs for perovskite solar cells by combining two design strategies: (1) the incorporation of multi-arm for mobility enhancement and (2) including Lewis bases that assist in defect passivation. Through multi-scale computations along with the analysis of electronic structure, molecular transport network and data clustering, we established the relationship between hole mobility, transport parameters, intrinsic molecular properties and molecular packing. Our results showed that multi-arm design can be an effective strategy for four-fold hole mobility enhancement (from 7×10-6 to 3×10-5 cm2V-1s-1) through reducing the reorganization energy and energetic disorder. Furthermore, ionization potential (IP) optimization by changing substituents was performed since the IP decreases with increasing number of arms. By adequate choice of substituents, the IP approaches the minus valence band maximum of MAPbI3 and the hole mobility is further increased by ~3 ti...