Enhanced efficiency of organic solar cells through trans-cinnamic acid doped cathode interface layer

Within organic solar cells (OSCs), the cathode interface layer (CIL) is indispensable for promoting the transport and extraction of charges. In this research, an environmentally friendly and cost-effective trans-cinnamic acid (TCA) is doped into PFN-Br to serve as the CIL in OSCs. The molecular structure and electronic structure of TCA were studied in this article using density functional theory (DFT) calculations executed with the Gaussian'16W software. The calculation results based on DFT indicate that TCA exhibits excellent planarity and the lowest unoccupied molecular orbital (LUMO) matching with PFN-Br. Excellent planarity and matched energy levels are advantageous for charge transport and harvesting. Doping TCA into the PFN-Br cathode interface layer improved charge extraction efficiency, and reduced charge recombination phenomena. Consequently, this led to a notable amplification in the maximum power conversion efficiency (PCE) of PBDB-T: IT-M -based non-fullerene devices, achieving an impressive 11.32%. This study furnishes an uncomplicated and cost-effective strategy for improving the PCE in OSCs.