Tuning CdSeTe/Sb stack properties through optimized pre-treatment processes

This work explores the impact of pre-treatment strategies on the compositional, structural, and electrical characteristics of CdSeTe/Sb stacks subjected to heat treatment prior to Sb incorporation. As-deposited and thermally pre-annealed CdSeTe/Sb samples retain near-target Se/(Se+Te) ratios (~0.19), whereas CdCl2 treatment induces partial Se redistribution (Se/(Se+Te)≈0.16), suggesting enhanced interdiffusion that may affect chalcogen-related defect states. Microstructural analysis shows that CdCl2 activation promotes recrystallization, enlarges grain size up to 6.4 µm, and drives a texture change from (220) to the thermodynamically stable (111) orientation, with minor oxide formation. Band gap values remain around 1.4 eV for all samples. Electrical measurements reveal that carrier dynamics are strongly affected by defect-mediated activation: the as-deposited sample exhibits high carrier concentration (NCV=1.5×1016 cm-3) but moderate mobility (µ=3.5×102 cm2/V.s), whereas pre-annealing enhances mobility and lowers carrier concentration (µ=3.6×103 cm2/V.s, NCV=1.7×1015 cm-3). Interestingly, CdCl2 pre-treatment slightly reduces carrier mobility while simultaneously increasing the carrier concentration (NCV =2.6×1015 cm-3), highlighting a trade-off between mobility and carrier activation. These results demonstrate that pre-treatment prior to Sb deposition in CdSeTe/Sb stacks critically governs carrier transport and electrical behavior, with direct implications for enhancing potential photovoltaic performance.