Self-assembled hollow nanosphere arrays used as low Q whispering gallery mode resonators on thin film solar cells for light trapping.

Optical micro/nano-spherical cavities can be designed to confine light by generating resonances in whispering gallery modes (WGM) and then couple them into the substrate through leaky modes, which can be potentially used in thin film solar cells for absorption enhancements. In this work, the transparent ZnO electrodes in a hollow nanosphere (HNS) structure were proposed as WGM resonators to trap sunlight for the absorption enhancement in silicon thin film solar cells. A low cost and high throughput template based technology was developed to fabricate the ZnO HNS arrays on the Si substrates. Significant simulated absorption enhancement has been demonstrated on the ZnO HNS arrays decorated thin film solar cell with an active layer down to 250 nm in thickness. A 9.3% enhancement in the short circuit current density can be achieved theoretically by comparing the ZnO HNS array modified amorphous Si thin film solar cell with an anti-reflection layer configured cell.