Semitransparent and bifacial ultrathin Cu(In,Ga)Se2 solar cells via a single-stage process and light-management strategy

Abstract

Semitransparent and bifacial photovoltaic (PV) technology has received considerable attention recently owing to its potential for energy-harvesting window applications. Ultrathin Cu(In,Ga)Se2 (CIGS) solar cells with transparent conducting front and rear electrodes, which enable partial visible light transmission, are considered promising candidates for this purpose. However, to realize improved performance, a variety of challenges, including fabrication processes, material selection, and device structure design, remain to be addressed. Here, the material properties and performance characteristics of semitransparent ultrathin CIGS solar cells prepared on two types of transparent conducting oxide (TCO) rear contacts, namely, textured SnO2:F and flat In2O3:Sn films, using a single-stage co-evaporation method, are reported. Comparative performance evaluations of devices with the different TCO rear contacts reveal that the single-stage process is a very effective method for fabricating high-performance semitransparent CIGS solar devices, and that light management plays an important role in devices with ultrathin CIGS absorbers. A textured polydimethylsiloxane (PDMS) layer with light-scattering and antireflection properties enhances the light absorption properties of the devices. The device (absorber thickness: 322 nm) prepared on the flat In2O3:Sn rear contact with the textured PDMS layer exhibits superior performance as compared to other state-of-the-art solar devices, with a conversion efficiency of 10.5% and an average visible transmittance of 12.3%.