Photodetectors (PDs) for weak light signal detection have wide applications for optical communication and imaging. Antimony sulfide (Sb2S3) as a nontoxic and stable light-sensitive material becomes a promising candidate for weak light PDs, which are developing in the direction of high response, high speed, and low cost. Herein, a self-powered Sb2S3 PD with the structure of FTO/TiO2/Sb2S3/Au is developed to achieve weak light detection for 300–750 nm visible light. We control the Sb2S3 thickness with about 460 nm to match depletion region width (438 nm) and obtain an excellent photoresponsivity and 3 dB bandwidth. Furtherly, we prepare pyramid structure polydimethylsiloxane (PDMS) on the illuminating surface to enhance the performance of weak light detection by light-trapping effects. The photocurrent of Sb2S3 PD with 20 μm-sized PDMS texture achieves 13.6% improvement compared with the control one. Under weak 530 nm light illumination of 1 μW cm–2, the self-powered Sb2S3 PD with PDMS achieves high responsivity (3.41 A W–1), large detectivity (2.84 × 1013 Jones), and ultrafast speed (15 μs). The present Sb2S3 PD and light-trapping strategy are expected to provide an alternative to future commercial weak light detection applications.

Sb2S3 has emerged as a promising light‐absorbing material due to its nontoxicity, low cost, high stability, and absorption coefficient. However, the absorption spectrum ranges and back‐contact barrier between Sb2S3 and Au strongly limit the device performance. p‐type Sb2Se3 has a similar lattice structure and properties as Sb2S3, obtaining absorption expansion and ohmic back contact. Herein, efficient all‐inorganic planar Sb2S3 solar cells with the addition of Sb2Se3 layers are fabricated. The functions of Sb2Se3 as cooperative absorber (400 nm) and hole transport layers (HTL, 80 nm) are further explored. Systematic characterizations indicate that the junction quality and depletion widths of the device with the addition of Sb2Se3 are improved by forming a p–i–n structure. As a result, the all‐inorganic Sb2S3 solar cell with a Sb2Se3 HTL greatly increases the power conversion efficiency from 2.7% to 5.8% and the fill factor from 40% to 55.4%. The additional Sb2Se3/Au interface with matched energy‐level alignments reduces the back‐contact barrier and facilitates hole transport and collection. The present design and methods promote the development of Sb2S3 solar cells.

Antimony sulfide (Sb2S3) with a 1D molecular structure has strong bending characteristics, showing great application potential in flexible devices. Herein, the flexible substrate‐structured Sb2S3 solar cells is developed and improve device performances by the back interface selenization. The high‐quality Sb2S3 film with an optimal thickness of 1.8 µm, ensuring efficient spectra utilization, is deposited on flexible Mo foils by the rapid thermal evaporation technique. To solve the issues of back interfacial recombination and charge transport, the 20 nm MoSe2 layer between Sb2S3 film and Mo foil is fabricated by substrate selenization in the tube furnace. Further investigations indicate that the MoSe2 layer improves the interfacial energy band alignments and induces the [hk1] orientation of Sb2S3 film, thereby passivating defects and enhancing the carrier transport capacity. The flexible solar cell in the structure of Mo foil/MoSe2/Sb2S3/CdS/ITO/Ag, exhibiting good flexibility to stand thousands of bending, achieves an efficiency of 3.75%, which is the highest for Sb2S3 devices in substrate configuration. The presented flexible structure and back interfacial selenization study will provide new prospects for inorganic Sb2S3 thin film solar cells.