Optimizing Solar Cell Performance: Hybrid Planar-Si/Organic Heterojunction Solar Cells Achieve 14.75% Efficiency Through Dibenzothiophene-Spirobifluorene-Dithienothiophene Insertion Layer Integration

Hybrid planar-Si/organic heterojunction solar cells have garnered substantial interest due to their potential for producing cost-effective, high-efficiency devices. This study investigates the photophysical properties and application of dibenzothiophene-spirobifluorene-dithienothiophene (DBBT-mCbz-DBT) in enhancing the efficiency of photovoltaic devices. Utilizing ultraviolet–visible and fluorescence spectroscopy, DBBT-mCbz-DBT is analyzed in solutions and doped films, showing maximum absorption at 380 nm and emission at 440 nm. Notably, the photoluminescence intensity in 4,4′-di(9H-carbazol-9-yl)-1,1′-biphenyl films peaks at 40–50% DBBT-mCbz-DBT concentrations, which are selected for solar cell fabrication. Enhanced light absorption and charge transport are observed with a DBBT-mCbz-DBT layer on silicon, significantly improving device performance. The planar silicon/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (Si/PEDOT:PSS) heterojunction solar cells with DBBT-mCbz-DBT exhibit a power conversion efficiency of 14.75%, demonstrating substantial gains over baseline structures. The DBBT-mCbz-DBT layer optimizes energy band alignment, reduces recombination losses, and enhances electron transport, improving overall device efficiency. This research underscores the potential of integrating DBBT-mCbz-DBT in solar cells to achieve higher performance through simple, scalable fabrication methods.