Abstract
To date, 21.7 % is the highest reported efficiency for inorganic Cu(In,Ga)Se2 (CIGS) thin-film photovoltaic solar cells (PV). However, the high temperature post-selenization process used in the fabrication of CIGS restricts its application on variety of low cost and flexible device substrates; in turn impeding the use of CIGS based PV in the next generation of consumer electronic products. In this work, a process enabling the direct transfer of conventional soda-lime glass (SLG) based CIGS devices onto arbitrary substrates has been developed and demonstrated. Raman analysis is performed to examine the material characteristics after the transfer process showing no significant differences, while Photoluminescence (PL) and X-ray Diffraction (XRD) show little distortion in the film crystallinity. Between the pre and post-transferred CIGS devices, 70% of power conversion efficiency is maintained. This approach utilizes a chemical-mechanical polishing (CMP)-like procedure to etch away the SLG used in the regular CIGS device structure, thus allowing the remaining device to be transferred to arbitrary substrates. SEM revealed the quality of CIGS films remain the same after the etching procedure. We demonstrate the transfer of our CIGS devices onto three different kinds of flexible substrate (Stainless steel, polyimide (PI) and paper) to establish the flexibility of our method. We believe that this approach can not only further stimulate the development of low cost flexible thin film solar cells, but also benefit the broader field of flexible electronics in general.