Impact of End-capped Acceptor Modification in Anthanthrone-Based D-π-A Type Donor Materials for Organic and as Hole...

Efficient hole-transporting materials (HTMs) are important for improving the stability and performance of all-small-molecules organic solar cells (ASM-OSCs) and perovskite solar cells (PSCs). However, low photovoltaic efficiencies, due to challenges in the designing of small molecular electron donors (SMEDs) with ideal energy levels, light absorption, and optoelectronic properties, hinder their widespread usage. This study presents an end-capped molecular engineering strategy to develop highly efficient HTMs for PSCs and donor materials for OSCs. The approach involves integrating acceptor-anchor groups via a thiophene spacer into the anthanthrone (ANT) core with triphenylamine side groups, leading to a series of six newly designed HTMs (AZU1-AZU6). Quantum simulations employing density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods were conducted to analyze their electronic and photophysical properties. The designed HTMs exhibit an impressive intrinsic charge transfer of 90% and small exciton binding energy (0.11-0.44 eV), facilitating efficient charge separation. The HOMO energy levels of the designed HTMs (- 4.96 to - 5.01 eV) show significant stabilization compared to the reference molecule (- 4.82 eV), promoting better energy level alignment with the perovskite absorber and PCBM polymer. Optical analysis reveals a broad and transparent absorption profile across the visible spectrum (573-737 nm in solvent), minimizing thermalization losses and optimizing light harvesting. The designed HTMs also exhibit smaller hole reorganization energies (0.1427-0.1513 eV) and higher transfer integrals (0.2251-0.2484), suggesting superior hole mobility. Moreover, their higher solvation-free energy values (-22.54 to -32 kJ/mol) indicate enhanced solubility and surface-wetting properties. Notably, the designed HTMs achieve higher open-circuit voltage (V_OC) values (1.57-1.62 V) compared to the reference (1.42 V), underscoring their potential for improved photovoltaic performance. Overall, this study highlights the promising role of ANT-based HTMs in advancing PSC and OSC technology through enhanced charge dynamics and optimized energy levels.