Grain growth enhancing through preheating treatment of a sputtered stacked metallic precursor for Cu(In, Al)Se₂ thin film solar cells application

The influence of preheating treatment of a sputtered stacked metallic precursor on structural property of the CuInAl precursor and detailed structural, morphological and optical analyses as well as in the finally obtained Cu(In, Al)Se₂ (CIAS) thin film solar cell device characterization are investigated systematically. These results indicate that this preheating process exhibits a strong beneficial impact on crystal growth and eventually produces a substantial improvement in photovoltaic properties. However, further increase of the preheating temperature, despite enhancing grain growth, clustering of grains loosely distribute on the surface of the CIAS thin film, forming a rather rough morphology. Thus, an accurate control of the preheating temperature during grain growth process may be necessary. Here, when optimizing the preheating temperature to 300 °C, the largest grain size and the best photovoltaic performance achieved. The findings provide an important insight into the understanding of fundamental research of current chalcopyrite solar cell application.