Abstract
Antimony trisulfide (Sb2S3) 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 Sb2S3 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 1020 cm−3. These features, together with polarized trap emission from Sb2S3 single crystal, strongly suggest that photoexcited carriers in Sb2S3 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 Sb2S3 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 Sb2S3 solar cells.
Highlights
Antimony trisulfide (Sb2S3) is considered to be a promising photovoltaic material; the performance is yet to be satisfactory
The exploration of semiconductor material for low-cost, stable, and efficient thin-film photovoltaics has been a key target for solar energy conversion
Together with polarized trap emission from single crystals, these results strongly suggest that photoexcited carriers are self-trapped by lattice distortion in Sb2S3
Summary
Antimony trisulfide (Sb2S3) is considered to be a promising photovoltaic material; 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 Sb2S3 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 1020 cm−3. Binary semiconductors antimony chalcogenides including Sb2S3 and Sb2Se3 emerge as promising materials due to their ideal bandgaps (Eg of 1.7 eV for Sb2S3 and 1.2 eV for Sb2Se3), large absorption cross-section, earth-abundance and environmentalfriendly and stable characters[1,2,3] They have fixed orthorhombic phase with infinite one-dimensional (1D) ribbons along the [001]. While fill factor (FF) up to 70% and near-unity internal quantum efficiency have been achieved, the open-circuit voltage (Voc) is surprisingly low, regardless of fabrication and pre/post-treatment methods[1,2,3]
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