Electron-selective contact design for pnictogen chalcohalide photovoltaics

Identify an electron-selective contact material, or engineer the conduction-band offset of CdS, V₂O₅, or MoSe₂ through approaches such as doping or interfacial dipole modification, to enable electron extraction from BiₓSb₁₋ₓSᵧSe₁₋ᵧI_zBr₁₋z solid-solution absorbers in photovoltaic devices with either the (010) or (011) surface orientation.

Background

The paper evaluates CdS, V₂O₅, and MoSe₂ as selective contacts for BiₓSb₁₋ₓSᵧSe₁₋ᵧI_zBr₁₋z solid-solution absorbers. Across both the (010) and (011) surface orientations, these materials are found to provide viable valence-band alignments only as hole-transport layers; no compatible electron-transport-layer alignment is identified.

Consequently, a functional photovoltaic architecture requires either discovering a genuinely electron-selective contact outside the three reference materials or modifying the conduction-band offset of one of them, for example through doping or interfacial dipole engineering. The authors explicitly identify this unresolved requirement as an open problem.