Multiarm and Substituent Effects on Charge Transport of Organic Hole Transport Materials

We explore several potential dopant-free triphenylamine-based hole transport materials for perovskite solar cells by combining two design strategies: (1) incorporation of multiple arms for mobility enhancement and (2) including Lewis bases that assist in defect passivation. Through multiscale computations along with the analysis of the electronic structure, molecular transport network, and data clustering, we established the relationship among hole mobility, transport parameters, intrinsic molecular properties, and molecular packing. Our results showed that multiarm design can be an effective strategy for 4-fold hole mobility enhancement (from 7 x 10(-6) to 3 x 10(-5) cm(2) V-1 s(-1)) through reducing the reorganization energy and energetic disorder. Furthermore, ionization potential (IP) optimization by changing substituents was performed because the IP decreases with an increasing number of arms. Via an adequate choice of substituents, the IP approaches the minus valence band maximum of MAPbI(3) and the hole mobility is further increased similar to 3-fold. The simulated mobility is in fair agreement with that obtained from field-effect transistors, supporting our computational protocols.