Modelling Insights of Sb₂(S,Se)₃ Solar Cells Using Triazatruxene Hole Transport Layers

Sb₂(S,Se)₃ is a promising thin-film solar absorber with a tunable bandgap (1.3–1.7 eV) and earth-abundant composition, yet its maximum reported efficiency (10.75%) in FTO/CdS/Sb₂(S,Se)₃/Spiro-OMeTAD/Au remains below the Shockley-Queisser limit. Moreover, the high cost of Spiro-OMeTAD as an HTL limits commercialization. Herein cost-effective triazatruxene-based HTLs (CI-B2, CI-B3, TAT-H, TAT-TY1, TAT-TY2) are introduced for the first time in Sb₂(S,Se)₃ solar cells and optimize device performance using SCAPS-1D. After replicating the experimental efficiency, optimization of HTL, ETL, and absorber parameters results in V_OC (≈1 V), J_SC >30 mA cm⁻²), and FF (72–74%). Overall, efficiencies of 22.97%, 23.09%, 22.47%, 21.08%, 23.24%, and 23.11% are achieved for Spiro-OMeTAD, CI-B2, CI-B3, TAT-H, TAT-TY1, and TAT-TY2, respectively, owing to the reduced V_OC loss (≈0.4 V), enhanced QE (>70%), reduced recombination (by a factor of 3 × 10¹⁸ cm⁻³s⁻¹), and stronger electric fields, positioning triazatruxene-based HTLs as a cost-effective alternative to Spiro-OMeTAD, significantly boosting Sb₂(S,Se)₃ solar cell performance.