The calculation of D-A-π-A-D hole transfer materials containing fluoranthene core for efficient perovskite solar cells

Abstract

In this work, an inexpensive, effective, and dopant-free hole transport material (HTM) of D-A-π-A-D (D=donor, A=acceptor) molecular configuration, called DTB-FL was selected as the basis and then different substitutes were introduced (SO3H, SiCl3, PO3H2, OC2F3, F, CO2H, CH2OH and H) on its central five-membered ring to replace C8H17 alkyl groups. These materials were applied as HTMs for ammonium-free Cs0.05FA0.95PbI3 perovskite solar cells (PSCs). Several properties of the designed HTMs were explored by density functional theory (DFT) and time-dependent DFT (TD-DFT) computations combined with Marcus theory for electron transfer, such as absorption and emission spectra, solubility, stability, reorganization energy, and hole mobility. Results showed that each designed HTM had a higher HOMO level than the perovskite valence band, allowing holes to be successfully injected into the HTM from perovskite. Moreover, theoretical results proved that all HTMs had LUMO energies very upper compared to perovskite conduction band, guaranteeing blocked electron flow effect from CsPbI3−xBrx towards cathode. In terms of VOC amounts, DTB-PO3H2 and DTB-SO3H were found to have the highest power conversion efficiency (PCE), open-circuit voltage (VOC), and fill factor (FF) amounts, which verified they were promising HTMs for the fabrication of PSC devices. Overall, it could be concluded that the designed HTMs had great potentials for PSC fabrication.