Exceeding 19% efficiency for inverted perovskite solar cells used conventional organic small molecule TPD as hole transport layer

In the fabrication of inverted perovskite solar cells (PeSCs), it is necessary to select an appropriate p-type semiconductive material as hole transport layer (HTL), which will determine the crystallization quality of the subsequent perovskite films and hole charge extraction at the perovskite/HTL interface. Herein, a low-cost, low-temperature processed, and hydrophobic organic small molecule, N,N-bis(3-methylphenyl)-N,N-bis(phenyl) benzidine (TPD), is utilized as HTL in fabricating inverted PeSCs. It achieves a peak power conversion efficiency of 19.77% by optimizing the thickness, which is about 1.4 times higher than the PeSCs employing poly(3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT:PSS) as HTL. Compared with PEDOT:PSS-based PeSCs, the outstanding performance of PeSCs-based TPD derives from that of the employment of TPD as the HTL produced perovskite films with larger grain size and higher crystallinity. Owing to the hydrophobicity of TPD, TPD-based PeSCs exhibited longer stability. After storage of 700 h, the PeCE of TPD-based PeSCs retains 84.1%.