A Modified Close-Spaced Sublimation Strategy Enabling Orientation Control and Defect Healing of Sb2S3 Indoor Photovoltaics.

Indoor photovoltaics (IPVs) offer a promising solution to the sustainable energy demand of Internet of Things (IoT) terminal devices. Among various IPV candidate absorbers, Sb2S3 stands out due to its ideal bandgap of approximately 1.75 eV, well-matching the spectral distributions of commonly used indoor light sources. Moreover, Sb2S3 has a high absorption coefficient, is eco-friendly, and has low-cost components, as well as a quasi-one-dimensional crystal structure that could offer high carrier transport if the crystal orientation could be well controlled. However, the performance of Sb2S3 solar cells has been limited by difficulty in controlling orientations and suppressing defects of Sb2S3 absorber films. In this work, a modified close-spaced sublimation strategy is explored to fabricate high-quality Sb2S3 films. Through systematic characterization of crystal structure, surface morphology, carrier dynamics, and photovoltaic performance, it is revealed that the resultant Sb2S3 films exhibit enhanced [hkl, l ≠ 0] preferred orientation and suppressed detrimental defects. Due to facilitated charge transport and suppressed carrier recombination, the all-vacuum processed planar heterojunction Sb2S3 solar cells yield a power conversion efficiency (PCE) of 4.09% under one-sun illumination and an indoor PCE of 10.04% under a 3000 K 1000 lux white light-emitting diode (WLED). This work proposes a facile strategy that allows effective orientation control and defect healing for vacuum processed Sb2S3 films and highlights great application potential of Sb2S3 IPVs for self-powered IoT systems.