Spectrum-Splitting Diffractive Optical Element of High Concentration Factor and High Optical Efficiency for Three-Junction Photovoltaics

Abstract

A spectrum-splitting and beam-concentrating (SSBC) diffractive optical element (DOE) for three-junction photovoltaics (PV) system is designed and fabricated by five-circle micro-fabrication. The incident solar light is efficiently split into three sub-spectrum ranges and strongly concentrated on the focal plane, which can be directly utilized by suitable spectrum-matching solar cells. The system concentration factor reaches 12×. Moreover, the designed wavelengths (450 nm, 550 nm and 650 nm) are spatially distributed on the focal plane, in good agreement with the theoretical results. The average optical efficiency of all the cells over the three designed wavelengths is 60.07%. The SSBC DOE with a high concentration factor and a high optical efficiency provides a cost-effective approach to achieve higher PV conversion efficiencies.

Effective bandwidth approach for the spectral splitting of solar spectrum using diffractive optical elements

“…By increasing the resolution in thickness of each pixel (similar to Ref. [7,18,19]) we can obtain greater SOE and enhancement values. By introducing the bandwidth approach, we designed a single broadband DOE that performs spectral splitting and concentration of broadband light.…”

“…Besides, the number of design wavelength causes an expensive computational load. In addition to computational calculations, thanks to microfabrication technologies these structures can be fabricated at high precision and low cost [7,18,19]. As expected better precision in fabrication results in greater spectral splitting efficiency and beam concentration.…”