Molecular Engineering of Tetraphenylbenzidine-Based Hole Transport Material for Perovskite Solar Cell.

Experimental and theoretical HOMO energy correlation of tetraphenylbenzidine (TPB)-based hole transport materials (HTMs) was successfully achieved through adiabatic ground-state oxidation potential calculation using LC-ωPBE. Similarly, trends in the computed excitation energies and hole reorganization energies of the HTMs are in agreement with the experimental band gaps and hole mobilities, respectively. Using these established correlations, the calculated properties of novel TPB-based HTMs were analyzed, and among the derivatives, TPB with attached fluorene (Fl) has less absorption in the visible region, a lower hole reorganization energy, and a deeper HOMO level compared to the reference. These properties signify that Fl could be a promising HTM in perovskite solar cells because this material will not compete with the perovskite absorption, will be efficient for hole transport due to its better hole mobility, and will eventually enhance the open-circuit voltage of the device. All of these factors could improve the efficiency of the perovskite solar cell.