Quantum designing of alkyl-silyl benzodithiophene-based hole transport materials for organic and perovskite solar cells

Rational discovery of hole‐transport materials (HTMs) for OSCs/PSCs benefits from prescreening that links molecular structure to energy alignment and intrinsic transport before synthesis. This study reports a computational prescreening of five benzodithiophene (BDT)-based HTMs, BDTP1–BDTP5, obtained by bridging-unit engineering of a reported BDTP scaffold for viable photovoltaics. Comprehensive molecular characterization of the designed HTMs was achieved through DFT/TD-DFT simulations to investigate their structural, electronic, photophysical, and charge transport properties. Computational results show that the molecular design strategy tunes highest occupied molecular orbitals (HOMO) from –5.953 to –5.430 eV and lowest unoccupied molecular orbitals (LUMO) from –3.740 to –3.081 eV, maintaining LUMOs well above typical perovskite conduction band maxima and enabling HOMO placement relative to representative valence band maxima by acceptor choice. Band gaps follow BDTP5 (1.69 eV) < BDTP4 (1.89 eV) < BDTP1 (2.17 eV) < BDTP2 (2.35 eV) < BDTP (2.45 eV) < BDTP3 (2.52 eV). In chloroform solvent, BDTP4/BDTP5 exhibit strong, red-shifted bands absorption maxima at 824/899 nm and reduced lower exciton binding energy (0.4207/0.3282 eV), consistent with backbone-spanning HOMO delocalization seen in FMO/TDM analyses. Transport descriptors identify low hole reorganization energy for the new HTMs and corresponding enhanced hole transfer rate of up to 4.85 × 10¹² s⁻¹, outperforming the BDTP reference and comparing favorably with the Spiro-OMeTAD benchmark under a uniform model. Overall, BDTP4 and BDTP5 emerge as the most promising HTMs by jointly optimizing energy-level alignment, optical response, and intrinsic hole-transport propensity within a single, synthetically modular motif. As a DFT/TD-DFT pre-screen, these results prioritize targets for future experimental synthesis and device testing.