Self-assembled Cu(In,Ga)Se2 nanocrystals formed by Ar ion beam irradiation

We developed a simple and effective method for the large scale formation of self-assembled Cu(In,Ga)Se2 (CIGS) nanocrystals by ion beam irradiation. The compositional changes and morphological evolution were observed as a function of the irradiation time. As the ion irradiation time increased, the nano-dots were transformed into a nano-ridge structure due to the competition between sputtering and diffusion processes during irradiation. In terms of the stoichiometry of the CIGS nano-dots, an increase in the Cu content was observed while the Se content decreased. The PL peak of the nano-dots formed CIGS thin film exhibited a blue-shift. Uniformly formed crystalline CIGS nano-dots can be adopted to increase the p–n junction area and the size confinement effect between the CdS and CIGS film in solar cell systems. This simple method can be exploited for band-gap engineering and enhancing photovoltaic properties.