Patterned honeycomb-like ZnO cavities for Cu(In,Ga)Se2 thin film solar cells with omnidirectionally enhanced light harvesting

•Patterned honeycomb-like ZnO cavities fabricated by NSL.•Light harvesting through scattering and coupling of the incident light.•Omnidirectional behavior in a wide incident angle range.•10.6% enhancement in the energy conversion efficiency is achieved.

A novel idea was presented by using patterned honeycomb-like ZnO cavities to enhance the light harvesting of Cu(In,Ga)Se2 (CIGS) thin film solar cells in a broadband wavelength range. Large-scale patterned honeycomb-like ZnO cavities were fabricated through the versatile colloidal lithograhpy technique combined with the subsquent hydrothermal growth reaction. The growth mechanism was proposed based on the structural evolution of the patterned ZnO cavities. By introducing the patterned honeycomb-like ZnO cavities into CIGS solar cells, the performances of the device can be remarkabley improved due to the enhanced light harvesting. Photovoltaic device with a standard soda lime glass (SLG)/Mo/CIGS/CdS/i-ZnO/AZO/ZnO cavities/Ag grid structure exhibited a maximum power conversion efficiency of 11.4% under the standard AM 1.5 global illumination with a light intensity of 100 mW/cm2. An improvement of over 9.0% in the short-circuit photocurrent density and a 10.6% enhancement in the energy conversion efficiency were achieved compared with the standard reference device without ZnO cavities. More importantly, the device with patterned ZnO cavities exhibited omnidirectional behavior within a wide incident angle range. The enhancement of light harvesting is originating from the novel “negative” configuration of patterned ZnO cavities, which can realize high-efficient light trapping by multiple scattering and light coupling.

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