Diffuse Solar Micro-Concentrators Using Dielectric Total Internal Reflection with Tunable Side and Top Profiles

Photovoltaics (PV) is one of the most promising and fast-developing renewable energy technologies thanks to the ubiquitous access to solar radiation around the globe, the nearly inexhaustible amount of solar energy, as well as the development in multi-junction PV that has increased the power conversion efficiency (PCE) above the single junction limits in the last half century. As traditional silicon solar cells have been widely utilized and commercialized, new efforts are focused on investigating the potential of PV in the use of various scenarios besides large, rigid and heavy rooftop solar panels. Lightweight and high-efficiency solar technologies could serve as ideal candidates for building-integrated photovoltaics (BIPV) and mobile power applications, which could be a strong complement to or even substitution for current installations. However, these next-generation solar technologies usually suffer from difficulty in making large-area uniform materials, high materials costs, and insufficient collection of the non-normal-incidence solar radiation.<br/>New solar concentrator designs that are able to collect non-normal-incidence radiation and diffuse light while maintaining high concentration factors are therefore a promising technology for realizing high-efficiency low-cost photovoltaic systems without the need for extra active tracking components. In this work, we develop a novel design for dielectric total internal reflection concentrators (DTIRCs) that utilizes a piecewise smooth sidewall profile, where an intermediate segment is inserted between two otherwise smooth segments. Coupled with a turning point in the top entrance surface, this design allows for a tunable phase shift between the two single segments. By tuning the phase shift and shape of the intermediate segment, both the acceptance angle and concentration ratio can be increased, potentially exceeding the limit imposed by etendue conservation. In addition, we calculate the annual collectible sun power for a realistic latitudinal position on the earth and prove that our new design receives more power compared to traditional direct concentrator and standard DTIRC designs, making it a good candidate for scalable micro-concentrator systems that can be integrated directly into a solar cell package.<br/>We then validate our new optical designs by manufacturing a mold via 3D printing technology and fabricate the concentrator out of molded Polydimethylsiloxane (PDMS). We measure its optical performance and integrate it with a commercial III-V solar cell to test ist concentrating power. Both the concentration ratio and the angular acceptance measurement results verify our simulation results. Our modified DTIRCs are therefore a promising enabling technology for the deployment of high-efficiency small-area solar cells for power generation in the practical circumstances found throughout the world outside of the tropics, where the majority of Earth’s population lives. The mechanical flexibility of our DTIRCs also paves the way to implementing solar technologies on a variety of complicated surfaces, as well as integrating them with multiple types of novel optoelectronic devices.