Xianzhong Lin

Defect study of Cu2ZnSn(SxSe1−x)4 thin film absorbers using photoluminescence and modulated surface photovoltage spectroscopy

Defect states in Cu2ZnSn(SxSe1� x)4 thin films with x ¼0.28, 0.36, and 1 were studied by combining photoluminescence (PL) and modulated surface photovoltage (SPV) spectroscopy. A single broad band emission in the PL spectra was observed and can be related to quasi-donor-acceptor pair transitions. The analysis of the temperature dependent quenching of the PL band (x ¼0.28, 0.36, and 1) and SPV (x ¼0.28) signals resulted in activation energies below 150meV for PL and about 90 and 300meV for SPV. Possible intrinsic point defects that might be associated with these observed activation energies are discussed. V C 2015 AIP Publishing LLC.

Lattice positions of Sn in Cu2ZnSnS4 nanoparticles and thin films studied by synchrotron X-ray absorption near edge structure analysis

Lattice positions of Sn in kesterite Cu2ZnSnS4 and Cu2SnS3 nanoparticles and thin films were investigated by XANES (x-ray absorption near edge structure) analysis at the S K-edge. XANES spectra were analyzed by comparison with simulations taking into account anti-site defects and vacancies. Annealing of Cu2ZnSnS4 nanoparticle thin films led to a decrease of Sn at its native and defect sites. The results show that XANES analysis at the S K-edge is a sensitive tool for the investigation of defect sites, being critical in kesterite thin film solar cells.

Correlation between processing conditions of Cu2ZnSn(SxSe1−x)4 and modulated surface photovoltage

Cu2ZnSn(SxSe1−x)4 (CZTSSe) layers deposited from multi-component nanoparticle inks were characterized by modulated surface photovoltage (SPV) spectroscopy to investigate the effect of annealing conditions. The SPV signals increased strongly with decreasing sulfur content. Band gaps were obtained in terms of SPV onset energy. A diffusion length of above 1 μm was estimated for photo-generated electrons at x = 0.28. The band gap increased with increasing x showing an anomaly in the range of 0.5 < x < 1. The results suggested that an excess of selenium is required for the formation of a photo-active phase reliable for efficient Cu2ZnSn(SxSe1−x)4-based solar cells.