Modulation of carrier dynamics via dual-hole transport layers in high-efficiency antimony selenide thin-film solar cells

Abstract

Antimony selenide (Sb₂Se₃) is a promising absorber material for thin-film solar cells due to its suitable bandgap and low cost. However, Spiro-OMeTAD (the commonly used organic hole transport layer) is expensive and unstable. Nickel oxide (NiO_X) has emerged as a more stable and cost-effective alternative and has demonstrated excellent applicability across various thin-film solar cells, including perovskite-based devices. Nevertheless, NiO_X exhibits poor hole transport capability and forms substantial back-contact barriers when interfaced with Sb₂Se₃ and gold electrodes. To overcome these limitations, we propose a dual-hole transport structure composed of phthalocyanine (Pc)/NiO_X. Pc exhibits a high carrier mobility and a valence band that aligns well with NiO_X, thereby facilitating efficient hole transfer and reducing interfacial barriers. NiO_X has a wide bandgap, which blocks electrons and suppresses recombination. This dual structure improves device performance, yielding a power conversion efficiency of 7.27% which outperforms single-layer NiO_X devices and demonstrates the advantages of our dual design.