Optical Microconcentrator System for Enhancing Solar Cell Photovoltaic Performances

In this paper, we present two optical microconcentrator systems consisting of an array of microlenses formed with an intermediate layer deposited between a textured glass plate and the front surface of a silicon solar cell and polydimethylsiloxane (PDMS) microlenses based on replication of molds etched on glass. The optical coupling microlenses are fabricated using simple photolithography techniques that make the design compatible with silicon technology and large-scale manufacturing.We experimented with a honeycomb texturization on Corning glass plate having an area of 2x2 cm2. A wet etching process that led to a transparent surface with micro-cavities of 20 μm diameter and a depth of 6 μm was used. The intermediate layer was chosen depending on the refractive index. Materials with the refractive index in the range of 1 - 1.43 were experimented. The structures of silicon solar cells covered with the intermediate layer and texturized glass were characterized by illuminating and measuring the short-circuit photocurrent. It was obtained an improvement of 6.7 % of the short-circuit photocurrent for the optical microconcentrator system solar cells as compared to a structure covered with an untextured glass plate without intermediate layer. The microconcentrator consisting of the PDMS microlenses gave better results, an increase of the photocurrent of over 9%.The simulations of this system were done by using an OptiFTDT software. The aim of the simulations was to establish the distribution of the radiation which crosses the optical microconcentrator system and hits the solar cells surface. The simulation results are in agreement with the obtained experimental data.