A simple system of grating lines can markedly improve the light trapping capabilities of solar cells, as demonstrated researchers from the University of York (U.K.), NOVA University of Lisbon (Portugal) and University of São Paulo (Brazil).

A checkerboard design tested on a 1 µm slab of crystalline silicon was observed to improve diffraction, enhance light absorption and boost electricity output. The bulk current of the silicon cell was increased by 125%.A checkerboard system of grating lines improves light trapping capabilities of solar cells. Source: Davide Zecca et al.

The design principle is based on criteria that link the Fourier series of a structure to its implied photocurrent. These parameters include the structural feature size, their periodicity and the etching depth. The researchers also emphasized the importance of the photonic domain size, or the region within a photonic structure in which a basic diffractive element is periodically arranged in a one-dimensional fashion, in achieving light trapping and efficiency gains.

The checkerboard design light trapping performance approached that of a super-cell design based on the superposition of multiple gratings that control the phase shift between different diffraction orders. The new arrangement is less complex and incurs much lower loss in light trapping performance.

The research is published in Optica.