A Tailored PbS/PbSe Double Hole Transport Layer for High-Performance Full-Inorganic Sb2S3 Indoor Photovoltaics

Abstract

The severe nonradiative recombination at the back-contact (BC) interface significantly hinders the enhancement of device performance in antimony sulfide (Sb₂S₃) solar cells. One of the attributable issues is the insufficient coverage rate of a single-layer hole transport layer (SHTL) and the energy-level mismatch at the back interface. To tackle the above challenges, this work proposes innovative bilayer hole transport layers (BHTLs) consisting of PbS and PbSe films. The BHTLs are sequentially deposited via continuous vacuum evaporation (CVE). Benefiting from the quantum size effect, their bandgaps are precisely tuned to 2.6 and 2.06 eV, respectively. Such a design greatly mitigates interfacial energy level mismatch and forms a well-optimized stepwise band alignment between the Sb₂S₃ light-absorbing layer and the carbon electrode. Moreover, the integration of the PbS/PbSe layers significantly enhances the device’s surface morphology to ensure high-quality interface contact with the carbon electrode. The adoption of this dual HTL can also effectively reduce the interface defect density of the device from 1.9 × 10¹⁶ to 9.7 × 10¹⁵ cm^–3, thereby suppressing nonradiative recombination. Ultimately, the solar cell with the FTO/TiO₂/CdS/Sb₂S₃/PbS/PbSe/Carbon architecture has attained a remarkable power conversion efficiency (PCE) of 7.62%, which is the record efficiency for carbon-based Sb₂S₃ solar cells. Notably, the device achieves an excellent PCE of 17.34% under indoor illumination of 1000 lx and exhibits outstanding stability. A series-connected module composed of 8 Sb₂S₃ cells delivers a high open-circuit voltage of 3.43 V under 1000 lx, fully meeting the operating voltage requirements of commercial EM4325 RFID sensor tags.