Forming Gas Annealing Improves the Performance of Ex Situ Sb-Doped CdSeTe Thin-Film Solar Cells

Group V doping in cadmium-selenide-telluride (CdSeTe) polycrystalline thin-film solar cells has demonstrated improved power conversion efficiencies (PCEs) and long-term stabilities as compared to the traditional Cu doping in the last decade. The dopants can be successfully incorporated by either in situ or ex situ doping. Here, we report that forming gas (FG) annealing enhances the efficiencies of CdSeTe polycrystalline thin-film solar cells utilizing ex situ antimony (Sb) doping via close-space sublimation of SbCl₃ at ambient pressure. The FG annealing increases the hole density and carrier lifetime, reduces the back barrier height, and, therefore, leads to improved open-circuit voltages (V_OCs) and fill factors (FFs). The champion device achieves a PCE of 19.2% with a V_OC of 877 mV, a current density (J_SC) of 30.2 mA/cm², and an FF of 72.4%. Importantly, the Sb-doped devices showed improved stability under stress tests as compared to Cu-doped devices.