Sb2S3 indoor photovoltaics with a charge-transport-layer-free sandwich-structure

Indoor photovoltaics (IPVs) attract tremendous attention for powering low-power electronics through harvesting light energy from indoor ambient environments. Sb2S3 is a promising IPV light-harvesting material with a theoretical power conversion efficiency (PCE) exceeding 47% under white LED (WLED) illumination. Here, we report a simple charge-transport-layer-free (CTL-free) sandwich-structure for Sb2S3 solar cells, featuring an innovative fluorine-doped tin oxide/Sb2S3/Au configuration that eliminates traditional planar heterojunction components like the commonly used CdS electron transport layer and Spiro-OMeTAD hole transport layer. Leveraging close-spaced sublimation technology combined with a seed-mediated two-step deposition strategy, high-quality Sb2S3 absorber layers with preferential [hk1] crystallographic orientations, compact surface morphology, and suppressed interfacial defects were obtained, confirmed by systematic structural, morphological, band structure, and transient spectroscopy characterization. Benefitting from the favorable charge-carrier transport and collection, the as-obtained CTL-free Sb2S3 solar cells yield an impressive PCE of 5.24% under 3000 K 1000 lux WLED illumination with superior long-term performance stability. This work reveals the possibility of designing CTL-free antimony chalcogenide solar cells with decent device efficiencies as well as the great potential for acting as indoor energy harvesting for sustainable Internet of Things systems.