After more than 20 years of research on rear side gratings for light trapping in solar cells, we have been able to demonstrate enhanced efficiencies for crystalline silicon solar cells with two different grating concepts and solar cell architectures. In both cases planar front sides have been used. With hexagonal sphere gratings and the tunnel oxide passivated contact (TOPCon) concept, a grating induced J_sc increase of 1.4 mA/cm² and an efficiency increase of 0.8%absolute could be achieved. With binary crossed gratings fabricated by a nanoimprint based process chain, a grating induced J_sc gain of 1.2 mA/cm² and an efficiency gain of 0.7% absolute could be achieved. For the binary grating concept, cell thickness variations have also been performed. The increasing importance of the light trapping properties towards low solar cell thicknesses could be confirmed by an enhanced EQE in the long wavelength region (J_sc increase: 1.6 mA/cm² for 150 μm and 1.8 mA/cm² for 100 μm thick solar cells). The results are in very good agreement with simulations using the OPTOS modeling formalism. OPTOS enables the further analysis and optimization of grating concepts in silicon solar cells and modules. So a grating induced J_sc gain of 0.8 mA/cm² is forecast for solar cells with pyramidal front side texture. On module level, still a grating induced J_sc gain of 0.6 mA/cm² can be expected.

Date Published: 29 April 2016
PDF: 9 pages
Proc. SPIE 9898, Photonics for Solar Energy Systems VI, 98980A (29 April 2016); doi: 10.1117/12.2228713

Published in SPIE Proceedings Vol. 9898:
Photonics for Solar Energy Systems VI
Ralf B. Wehrspohn; Andreas Gombert, Editor(s)