A critical review on flexible Cu(In, Ga)Se2 (CIGS) solar cells

The development of flexible Cu(In, Ga)Se2 (CIGS) solar cells opens new markets for indoor and outdoor applications, and thus has become one of the major directions for present research. Although the efficiency gap between glass and flexible substrates can now be reduced on a flexible polyimide through KF post-deposition treatment, it still seems difficult to transfer research-level technologies to industrial applications. Therefore, in this article, except for the progress made on different flexible materials, we discuss the feasibility of laser scribing and durability of transparent electrodes on flexible substrates. Finally, we provide an overview of the emerging technologies including cracked selenium sources and lift-off processes that may be applied for other flexible low-temperature substrates in the future. •Laser scribing techniques for flexible CIGS modules are discussed.•The progresses of CIGS solar cells on different flexible substrates has been summarized.•Alternative transparent electrodes for flexible CIGS solar cells have been reviewed.•With selenium radicals or lift-off processes, the temperature limitation can be overcome.