Narrow bandgap CIGS solar cells on flexible, light weight glass

Abstract

CIGS absorbers with a near-infrared bandgap make excellent candidates for a bottom cell in multi-junction solar cell designs. These devices, available in flexible and lightweight form factors, have the potential to fuel numerous integrated solar cell applications. We successfully utilized a two-step method to synthesize CIGS on ultra-thin bendable glass with a bandgap ranging from 1.00 to 1.13 eV. Our process is homogenous, repeatable, and produces minority carrier lifetimes of up to 100 ns. We have also developed both conventional and alternative fabrication methods that have low waste and toxic footprints. Our champion solar cells, based on absorbers with a graded bandgap between 1.05 and 1.1 eV, have an open circuit voltage of nearly 600 mV. Our results demonstrate a scalable method for producing all thin-film, flexible tandem solar cells utilizing cost-effective and sustainable processing steps.