Improvement of the conversion efficiency and power of thin film silicon solar cells by embedding metallic nanostructures in depletion region

Abstract

In this paper we present a full wave 3D-finite difference time domain (FDTD) optical and electrical simulation study of ultra thin silicon solar cell. We have analyzed the optical generation rate and absorption enhancement in thin film solar cell in which silver nanoparticles are embedded in the depletion region of p-n junction in the active layer of solar cell. Then we investigate efficiency and power output of solar cell by solving the Poisson and drift diffusion equations on a finite element mesh, by considering the extracted generation rate data from FDTD simulations. In this work localized surface plasmons (LSPs) are the key factor for absorption and electron-hole generation rate enhancement in thin film solar cell. We show that these enhancements result from dense near field provided by LSPs and ensuring that a large fraction of the incident optical power (which is considered to be AM1.5) dissipates in the absorbing active layer rather than in the MNPs. We study in detail the effect of metal nanoparticle (MNP) geometry in solar cell performance and optimize geometrical parameters of MNPs through particle swarm (PS) optimization algorithm. The optimized structure of spherical MNPs with a diameter of 70nm and spacing of 180nm, and optimized structure of nanorod MNPs with a diameter of 70nm and center to center spacing of 190nm and length of 150nm which are imbedded in depletion layer, provided 32.83% and 39% improvements in the efficiency relative to the reference cell, respectively.