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CdTe Solar Cells: Processing Limits and Defect Chemistry Effects on Open Circuit Voltage
Published online by Cambridge University Press: 28 August 2013
Abstract
The role of CdTe solar cell processing on the defect chemistry that limits open circuit voltage (VOC) is addressed in the thermochemical processing regimes commonly encountered in present-generation CdTe devices. The highest VOC is 0.91 V for a bulk CdTe crystal with ITO which is only marginally higher than VOC = 0.86 V obtained for polycrystalline CdTe films with CdS. Both fall ∼0.4 V short of the VOC expected for CdTe, having band gap EG = 1.5 eV. The present >16% efficient superstrate CdTe cell uses a process based on high-temperature, T > 500°C, CdTe growth on CdS, coupled with optimized methods for incorporating oxygen, sulfur, copper, and chloride species in the CdTe film. Pushing cell conversion efficiencies beyond 20% will require increasing VOC beyond 1V. However the present pathway of processing optimization will likely yield VOC and efficiency converging on 0.9 V and <20%, respectively.
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- Copyright © Materials Research Society 2013
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