Enhanced antibonding coupling enables optical transparency in p-type semiconductors by orbital engineering

Abstract

Developing high-performance p-type transparent conducting materials (TCMs) remains challenging due to the intrinsic trade-off between a high valence band maximum (VBM), required for efficient acceptor ionization, and a wide bandgap for optical transparency. Motivated by the strongly p-type photovoltaic absorber Cu2ZnSnS4 (CZTS), we find that replacing Sn-5s with Si-3s orbital forming Cu2ZnSiS4 (CZSiS) significantly elevates the conduction band minimum through enhanced Si-3s/S-3p antibonding interaction, thereby enabling optical transparency. Meanwhile, CZSiS preserves the high VBM of CZTS, arising from Cu-3d/S-3p antibonding states, which facilitates the formation of CuZn− acceptors, analogous to CZTS. First-principles calculations demonstrate that CZSiS exhibits intrinsic p-type transparent conductivity with an electrical conductivity of 6.53 S/cm along with an optical transmittance of ∼80%. The isostructural compound Cu2MgSiS4 (CMSiS) further confirms the generality of this approach. This study proposes CZSiS and CMSiS as promising candidates for high-performance p-type TCMs and highlights orbital engineering as an effective strategy for transforming p-type semiconductors into efficient TCMs.