Tailoring charge transport in perovskite photovoltaics via chalcogen-thiophene molecular bridges

We present in this research the theoretical design and development of a Lewis base molecule, n-Bu4S, formed of fused thiophene units bridged by tetra-pyridine, as a versatile interfacial passivation layer for perovskite solar cells (PSCs). Strong host-guest interactions between n-Bu4S and under-coordinated Pb²⁺ essentially reduce interfacial recombination, hence improving charge extraction and device stability. Then, a typical structure based on ITO/SnO₂/perovskite/n-Bu4S/Spiro-OMeTAD/Au PSCs is proposed and simulated. Using SCAPS-1D numerical simulations shows that adding n-Bu4S greatly enhances the built-in potential, charge carrier kinetics, and overall device performance. The best-performing devices attained a simulated power conversion efficiency (PCE) of 24%. Furthermore, device-level investigations displayed the important effect of adjusting parameters such as perovskite thickness, defect density, carrier mobility, and shallow acceptor concentration. The simulated Nyquist analysis confirmed enhanced recombination resistance for the n-Bu4S-treated device. The results underline the need for interfacial and bulk engineering to obtain efficient and thermally stable PSCs, hence positioning n-Bu4S as a potential method for next-generation perovskite photovoltaics.