Light trapping for a-Si:H/µc-Si:H tandem solar cells using direct pulsed laser interference texturing

We present a-Si:H/µc-Si:H tandem solar cells on laser textured ZnO:Al front contact layers. Direct pulsed laser interference patterning (DLIP) was used for writing arrays of one-dimensional micro gratings of submicron period into ZnO:Al films. The laser texture provides good light trapping which is indicated by an increase in short-circuit current density of 20% of the bottom cell limited device compared to cells on planar ZnO:Al. The open-circuit voltage of the cells on laser textured ZnO:Al is almost the same as for cells on planar substrates, indicating excellent growth conditions for amorphous and microcrystalline silicon on the U-shaped grating grooves. DLIP is a simple, single step and industrially applicable method for large area periodic texturing of ZnO:Al thin films. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)