Monolithically interconnected lamellar Cu(In,Ga)Se2 micro solar cells under full white light concentration

Abstract

Thin film solar cells already benefit from significant material and energy savings. By using photon management, the conversion efficiency and the power density can be enhanced further, including a reduction of material costs. In this work, micrometer-sized Cu(In,Ga)Se2 (CIGS) thin film solar cells were investigated under concentrated white light illumination (1–50×). The cell design is based on industrially standardized, lamellar shaped solar cells with monolithic interconnects (P-scribe). In order to characterize the shunt and serial resistance profiles and their impact on the device performance the cell width was reduced stepwise from 1900 to 200 µm and the P1-scribe thickness was varied between 45 and 320 µm. The results are compared to macroscopic solar cells in standard geometry and dot-shaped microcells with ring contacts. Under concentrated white light, the maximal conversion efficiency could be increased by more than 3.8% absolute for the lamellar microcells and more than 4.8% absolute in case of dot-shaped microcells compared to their initial values at 1 sun illumination. The power density could be raised by a factor of 51 and 70, respectively. But apparently, the optimum concentration level and the improvement in performance strongly depend on the chosen cell geometry, the used contact method and the electrical material properties. It turns out, that the widely used industrial thin film solar cell design pattern cannot simply be adapted to prepare micro-concentrator CIGS solar modules, without significant optimization. Based on the experimental and simulated results, modifications for the cell design are proposed.