Hole-Transport Layer Molecular Weight and Doping Effects on Perovskite Solar Cell Efficiency and Mechanical Behavior

The effect of tuning molecular weight (M_n) in poly­[bis­(4-phenyl)­(2,4,6-trimethylphenyl)­amine] (PTAA) to increase both mechanical properties of the film and electrical properties of perovskite solar cells is reported. Perovskite solar cell devices are fabricated to investigate the effect of M_n on power conversion efficiency. Moisture stability for various M_n is also studied in PTAA films exposed to mechanical loads in humid environments. Furthermore, cohesion and tensile tests are employed to determine the mechanical properties of PTAA, where higher M_n leads to more robust films. To elucidate the effect of M_n on the debonding kinetics, a viscoelastic fracture kinetic model is proposed as a function of M_n, and the debonding mechanism is found to be dependent on M_n. Finally, the effect of small-molecule-based dopants on the mechanical stability of PTAA is investigated.