Interdiffusion of CdS and Zn2SnO4 layers and its application in CdS/CdTe polycrystalline thin-film solar cells

Abstract

Toward a high Cu2ZnSnS4 solar cell efficiency processed by spray pyrolysis method J. Renewable Sustainable Energy 5, 053137 (2013); 10.1063/1.4825253 Dependence of efficiency of thin-film CdS/CdTe solar cell on optical and recombination losses J. Appl. Phys. 113, 093105 (2013); 10.1063/1.4794201 Impedance spectroscopy of thin-film CdTe/CdS solar cells under varied illuminationIn this work, we found that the interdiffusion of the CdS and Zn 2 SnO 4 ͑ZTO͒ layers can occur either at high temperature (550-650°C) in Ar or at lower temperature (400-420°C) in a CdCl 2 atmosphere. By integrating a Zn 2 SnO 4 film into a CdS/CdTe solar cell as a buffer layer, this interdiffusion feature can solve several critical issues and improve device performance and reproducibility of both SnO 2 -based and Cd 2 SnO 4 -based CdTe cells. Interdiffusion consumes the CdS film from both the ZTO and CdTe sides during the device fabrication process and improves quantum efficiency at short wavelengths. The ZTO film acts as a Zn source to alloy with the CdS film, which results in increases in the band gap of the window layer and in short-circuit current density J sc . Interdiffusion can also significantly improve device adhesion after CdCl 2 treatment, thus providing much greater process latitude when optimizing the CdCl 2 process step. The optimum CdCl 2 -treated CdTe device has high quantum efficiency at long wavelength, because of its good junction properties and well-passivated CdTe film. We have fabricated a Cd 2 SnO 4 /Zn 2 SnO 4 / CdS/CdTe cell demonstrating an NREL-confirmed total-area efficiency of 15.8% (V oc ϭ844.3 mV, J sc ϭ25.00 mA/cm 2 , and fill factorϭ74.82%). This high-performance cell is one of the best thin-film CdTe solar cells in the world.

Synthesis and photoluminescence of Zn2SnO4 nanowires

“…Up to now, most researches have focused on the synthesis and application of Zn 2 SnO 4 films and nanoparticles. For example, integration of Zn 2 SnO 4 thin film in CdS/CdTe solar cell as buffer resulted in improved device performance [13]. Zn 2 SnO 4 nanoparticles have been used as photocatalysts for degradating organic pollutant [14,15] and as anode in Li-ion batteries [16,17].…”

Nanostructured CdS:O film: preparation, properties, and application

“…However, reducing the CdS thickness can adversely impact device open-circuit voltage (V oc ) and fill factor (FF). We have previously reported that by integrating a high-resistivity zinc stannate (ZTO) buffer layer between the poly-CdS and poly-CdTe films, we can minimize these detrimental effects [4]. Third, there is a nearly 10% lattice mismatch between the poly-CdTe film and the poly-CdS film, which causes the high defect density at the junction region.…”

Structural, electrical and surface morphological studies of Cd2SnO4 and Mg doped Cd2SnO4 thin films

“…The most popular TCO, tin-doped indium oxide (ITO) has some shortcomings limiting its applications in PVs and OLED structures [2,3]. This stimulated an intense research on alternative TCO materials and is now the subject of numerous investigations for alternative material to ITO for PVs device structures [4]. From the literatures, Cd 2 SnO 4 thin films are an n-type defect semiconductor material exhibiting promising properties such as low metallike electrical resistivity (10 -6 :m) and high transmission (>90%) in the visible range of the light spectrum and high reflectivity in the IR range.…”