Enhancing PCE above 16.03% via linker engineering of donor layer: A DFT study of binary all-small-molecule organic solar cells

Abstract

This study investigates the optical and photovoltaic properties of small molecule donors (SMDs) designed by the linker group replacement of a reported SMD (16.03 %) for use in the binary all-small-molecule organic solar cells (ASM-OSCs). The molecular geometries and reactivity parameters confirmed the ideal planarity, stability, and reactivity of designed SMDs. Using UV–Vis spectroscopy, the absorption spectra of these SMDs were analyzed in solvent and gaseous state to assess the optical properties. The study also evaluates transition state properties, revealing efficient charge transfer from donor to acceptor segments. Factors affecting charge mobility were calculated, demonstrating that all new SMDs, particularly H7, exhibit lower binding energy and favorable charge mobility compared to the original donor. The photovoltaic parameters show that all the designed SMDs, especially H7, achieve higher open circuit voltage, fill factor, and current density, suggesting improved PCE. Moreover, H7:PC71 BM, H7:ITIC, and H7:Y6 blends were assessed, confirming the efficient charge transfer characteristics. Overall, the study confirms that the structural modifications in the original SMD led to enhanced optoelectronic properties, and all the designed SMDs, particularly H7, would have a PCE greater than 16.03 %.