Performance of a 4-Terminals Spectral Splitting Asymmetric Solar Concentrator in Diffuse Sunlight: a Numerical Study

We numerically analyze the performance of a spectral splitting low concentrator under diffuse sunlight. The optics is the core of a 4-Terminal (4T) dual-junction PV architecture, with a wedged right-angled prism asymmetric concentrator and NIR and VIS cells respectively coupled to the bottom and the rear sides of the wedge. The spectral splitting approach relaxes the geometrical and technological constraints typical of tandem configurations. Light guiding is achieved by combining Total Internal Reflection and dichroic reflection, and skew incident rays become fully confined. Perfect optical coupling is supposed. Optical performance depends on the concentration ratio, set by the value of the apex angle of the wedge, on the input spectral content and on the spectral selection performed by the dichroic mirrors. Optical power ratio exceeding 60% can be achieved for diffuse input light. In the case of a HJT silicon cells and a GaAs single junction reference cell, by using license plate data for the electrical parameters of the cells, the Power Conversion Efficiency of the diffuse component in clear sky conditions amounts to around 30%, reaching up to 45% in case of overcast conditions. This geometry also minimizes self-shading and appeals to integrated and bifacial PV applications.