Antimony selenide (Sb₂Se₃) has recently made considerable advancements in photovoltaic, photoelectrochemical, and photodetector research scenarios, owing to its advantageous material merits and superior optoelectronic properties. By contrast, the exploration of flexible Sb₂Se₃ photoelectric devices are less attempted, though it possesses unique one-dimensional (1D) crystal structure to enable large deformation tolerance. Here, we develop a flexible Sb₂Se₃ thin-film photodetector on polyimide substrate. Thanks to the high-quality Sb₂Se₃ light absorber and benign interfaces at both back contact and heterojunction regions, the carrier dynamics are effectively optimized. The leading flexible Sb₂Se₃ photodetector showcases self-powered and broadband features, with exceptional responsivity of 0.51 A·W^–1 and realistic detectivity up to 1.32 × 10¹³ Jones, ultra-fast response speed of 49 ns/351 ns of rise and decay times, and remarkable mechanical deformation stability, flourishing the high-level development for flexible Sb₂Se₃ photodetectors. Interestingly, a tunable single/dual-color flexible imaging system under band alignment modulation, along with a wearable and accurate heart rate/arterial blood oxygen saturation photoplethysmography detection system highlights the great application potential for flexible Sb₂Se₃ photodetectors.

Antimony selenide (Sb₂Se₃) semiconducting material possesses a band gap of 1.05–1.2 eV and has been widely applied in single-junction solar cells. Based on its band gap, Sb₂Se₃ can also be used as the bottom cell absorber material in tandem solar cells. More importantly, Sb₂Se₃ solar cells exhibit excellent stability with nontoxic compositional elements. The band gap of organic–inorganic hybrid perovskite is tunable over a wide range. In this work, we demonstrate for the first time a perovskite/antimony selenide four-terminal tandem solar cell with a specially designed and fabricated transparent electrode for an optimized spectral response. By adjusting the thickness of the transparent electrode layer of the top cell, the wide-band-gap perovskite top solar cell achieves an efficiency of 17.88%, while the optimized antimony selenide bottom cell delivers a power conversion efficiency of 7.85% by introducing a double electron transport layer. Finally, the four-terminal tandem solar cell achieves an impressive efficiency exceeding 20%. This work provides a new tandem device structure and demonstrates that antimony selenide is a promising absorber material for bottom cell applications in tandem solar cells.

Poly(3-hexylthiophene) (P3HT), as a traditional organic hole-transporting material (HTM), is widely used in thin-film solar cells due to its high charge mobility and good thermal stability. However, the P3HT films obtained by the traditional method are amorphous, which is unfavorable to hole extraction and transport. Here, a low-toxicity solvent 1,2,4-trimethylbenzene (TMB) was used as the solvent instead of the commonly used halogen solvent chlorobenzene (CB) to dissolve P3HT. Thus, the self-assembled nanofibrous P3HT film was prepared and applied as HTM in the newly emerged Sb₂S₃ solar cells. According to the density functional theory calculations, the interface contact between TMB-P3HT and Sb₂S₃ was enhanced via the bonding interaction of S in P3HT and Sb in Sb₂S₃. Through transient absorption spectroscopy characterization, the enhanced interface contact improves the charge extraction ability of TMB-P3HT when compared to the CB-P3HT film. Thus, the TMB-P3HT-based Sb₂S₃ solar cell delivers a power conversion efficiency of 6.21%, which is 9.7% higher than that of the CB-P3HT-based device. Furthermore, the dopant-free TMB-P3HT-based Sb₂S₃ devices exhibit excellent environmental stability compared with Spiro-OMeTAD-based devices. This work demonstrates that the application of P3HT and the solvent engineering of HTM are applicable strategies for developing Sb₂S₃ solar cells with high efficiency and stability.