Ultrafast self-trapping of photoexcited carriers sets the upper limit on antimony trisulfide photovoltaic devices

• Published in: Nature communications Vol. 10; no. 1; pp. 4540 - 8
• Main Authors: Yang, Zhaoliang, Wang, Xiaomin, Chen, Yuzhong, Zheng, Zhenfa, Chen, Zeng, Xu, Wenqi, Liu, Weimin, Yang, Yang (Michael), Zhao, Jin, Chen, Tao, Zhu, Haiming
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 04.10.2019; Nature Publishing Group; Nature Portfolio
• Subjects: 140/125; 639/301/299/946; 639/638/440/949; Antimony; Carrier density; Crystal defects; Efficiency; Energy conversion efficiency; Humanities and Social Sciences; multidisciplinary; Open circuit voltage; Photoluminescence; Photons; Photovoltaic cells; Photovoltaics; Science; Science (multidisciplinary); Single crystals; Solar cells; Spectroscopy; Thin films; Trapping; Voltage
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-019-12445-6

Antimony trisulfide (Sb 2 S 3 ) is considered to be a promising photovoltaic material; however, the performance is yet to be satisfactory. Poor power conversion efficiency and large open circuit voltage loss have been usually ascribed to interface and bulk extrinsic defects By performing a spectroscopy study on Sb 2 S 3 polycrystalline films and single crystal, we show commonly existed characteristics including redshifted photoluminescence with 0.6 eV Stokes shift, and a few picosecond carrier trapping without saturation at carrier density as high as approximately 10 20  cm −3 . These features, together with polarized trap emission from Sb 2 S 3 single crystal, strongly suggest that photoexcited carriers in Sb 2 S 3 are intrinsically self-trapped by lattice deformation, instead of by extrinsic defects. The proposed self-trapping explains spectroscopic results and rationalizes the large open circuit voltage loss and near-unity carrier collection efficiency in Sb 2 S 3 thin film solar cells. Self-trapping sets the upper limit on maximum open circuit voltage (approximately 0.8 V) and thus power conversion efficiency (approximately 16 %) for Sb 2 S 3 solar cells. Antimony trisulfide has a proper bandgap of 1.7 eV for making solar cells but the devices suffer from severe voltage loss. Here Yang et al. propose that the photoexcited carriers are self-trapped by lattice deformation, which places a thermodynamic limit of only 0.8 V for the open circuit voltage.