Cadmium and Zinc‐Doped p‐type Sb₂Se₃ Single Crystals and Solar Cells

Achieving controlled p‐type doping in Sb₂Se₃ is critical for its development as a photovoltaic absorber. In this work, the incorporation of Cd and Zn as extrinsic dopants in Sb₂Se₃ single crystals and thin films, with concentrations ranging from 10¹⁶ to 10²⁰ cm⁻³, is investigated. Both dopants successfully induce p‐type conductivity, but Cd consistently yields lower resistivities and avoids compensation over a wider range of dopant concentrations. Cd‐doped Sb₂Se₃ single crystals exhibit hole densities exceeding 10¹⁵ cm⁻³, while thin films achieve over 10¹⁶ cm⁻³, values suitable for efficient solar cell operation. A shallow 22 meV Cd_Sb acceptor level appears to be compensated by a deeper lying state around 389 meV, which is intrinsic to Sb₂Se₃ and limits the achievable free hole concentration. Despite this, solar cells fabricated using Cd‐doped Sb₂Se₃ (at 10¹⁸ cm⁻³) show enhancements in open‐circuit voltage by ≈60 and ≈20 mV for devices prepared via thermal evaporation and close‐spaced sublimation respectively, relative to n‐type Cl‐doped Sb₂Se₃. These results establish Cd as a promising dopant for enabling robust p‐type conductivity and enhancing the photovoltaic performance of Sb₂Se₃‐based devices.