High‐Resistance Metal Oxide Window Layers for Optimal Front Contact Interfaces in Sb₂Se₃ Solar Cells

Herein, an in‐depth experimental investigation into the effect of employing different high resistance metal oxide (HRMO) layers on the quality of the front contact in solar cells with an fluorine‐doped tin oxide (FTO)/(HRMO)/CdS/Sb₂Se₃/Au device architecture is presented. The application of ZnO or TiO₂ HRMO layers between FTO substrates and CdS improves the overall device performance. Short‐circuit current gains of ≈20%, orders of magnitude higher shunt resistances (≈10⁴ Ω cm²), and greatly improved device stabilities—maintaining over 95% of their initial efficiency over 137 days are observed. A suppression of the unfavorable (120) orientation of the photoactive Sb₂Se₃ layer is observed in devices with HRMO interlayers. The application of HRMO layers is crucial to prevent both ohmic and non‐ohmic current leaks and maintain device stability over time. Cross‐over in the current‐voltage (JV) curves observed in the case of TiO₂ indicates the presence of a high barrier for the diode current in these devices. Wavelength‐dependent JV curves coupled with capacitance measurements and simulations show that this barrier can be attributed to a high density of interfacial acceptor states. In contrast, ZnO deposition is found to reduce interface defects and enhance the quality of the front contact, while boosting performance and increasing device longevity.