Performance Enhancement of Thin Film Solar Cell Using Two-Dimensional Plasmonic Grating in Rear Electrode

An effective scheme is proposed and investigated to improve the performance of thin film solar cells using a two-dimensional (2-D) plasmonic grating structure at the rear electrode or back metal contact. The proposed light trapping scheme replaces the conventional flat rear electrode by a corrugated electrode with a square mesh of periodic grooves forming a 2-D plasmonic grating. The grating surface diffracts the light and increases the path for reflected light. Further, the energy of surface plasmons excited inside the grooves gets coupled to the absorber layer. An efficient light trapping scheme and surface plasmons resonance conjointly increase the absorption in the absorber layer of solar cell, which results as enhanced efficiency. Maximum contribution of light path enhancement and surface plasmons is achieved by optimizing the periodicity, width, and depth of the grooves. The proposed design is compared with the conventional simple solar cell as well as with the solar cell having the rear electrode with 1-D plasmonic grating structure to demonstrate the effectiveness of the scheme. Finally, the optimized design is proposed which exhibits 92% absorption, 43% enhanced light path and more than 200% increase in the short circuit current as well as conversion efficiency.