Surface texturing of Cu2ZnSnSe4 thin films for enhanced optical absorbance

Thin-film solar absorber layer presenting its surface with periodically patterned structures or with random roughness are considered one of the ways to increase the incident light absorption and thereby enhance the performance of the solar cell. This surface modification in the absorber layer reduces the reflection loss and leads to multiple reflections of the photons that fall on the absorber layer, leading to improved absorbance. In this present work, optical lithography process has been adapted to achieve periodic micro patterning of Cu2ZnSnSe4(CZTSe) solar absorber thin film surface and the changes in optical absorbance is studied. Optimization of the lithography process is undertaken to upscale the area of patterning up to (similar to 20 mm x 20 mm) in CZTSe absorber thin films. CZTSe films were grown using e-beam evaporation and surface patterning is integrated through lithography process. Patterning integrity was examined through optical and scanning electron microscopes. Phase integrity was studied using XRD and Raman spectroscopy tools. The optical absorbance of the flat and patterned CZTSe thin films are measured using UV-Vis-NIR spectrophotometer.