Plasmon Enhanced Light Trapping for Thin Film Silicon Solar Cells Application Pushpa Ra j Pudasaini 1* and Arturo A Ayon MEMS Research Lab, Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, Texas, 78249, USA ABSTRCT -In this paper, the localized surface plasmon effect of gold (Au) nanoparticles deposited on the silicon nanohole (SiNH) array textured surface is studied via simulation for better light trapping purpose for thin flm silicon solar cells application. The ultimate efciency of the optimized SiNH array textured surface is increased by 27.5% with the inclusion of Au nanoparticles on its surface. The highest ultimate efciency of the proposed geometry herein (39.67 %) is still 12.8% greater than the single layer antirefection (AR) coating of Si3N4 on SiNH array textured surface without Au nanoparticles. The forward scattering of incident radiation by the Au nanoparticles near their localized plasmon resonance is responsible for the strong feld enhancement in the substrate and hence the higher ultimate efciency of the solar cell. Inde Tem - Light trapping, thin flm, silicon solar cells, antirefection coating. I. INTRODUCTION Single junction, crystalline silicon (c-Si) solar cell, in spite of their relatively high cost (�$5.50 per watt) has captured more than eighty percent of the current solar cell market, due to their relatively high efciency. But, cost is the main impediment for solar cells to capture a larger market share. Thus, identifing and demonstrating practical schemes to achieve device efciencies comparable to c-Si while reducing manufacturing costs is considered the greatest challenge that needs to be overcome. The high cost of c-Si structures originates on its poor infared absorption that arises fom its indirect band gap, which has driven the geometry of wafer based silicon solar cells to include a c-Si active layer of thickness 180-300 f.m. This relatively thick layer is employed as the means to absorb light effectively and, hence, increase device efciency, but it also accounts for nearly forty percent of the total device cost. In order to address the challenge of bringing the cost down while attempting to achieve reasonable effciencies, thin flm solar cells have been extensively characterized mostly because they are considered an alterative low cost photovoltaic choice of, approximately, less than $ 1 per watt. However, thin-flm structures routinely exhibit a lower efciency than their traditional wafer based c Si counterparts. Thus, to increase the optical absorption of thin-flm solar cells, various geometry confgurations including randomly [ 1] or periodically [2-8] textured surfaces, nanoparticle arrays and plasmonic structures [9- 12] have been intensively studied. Furthermore, noble metal nanopatricles 978-1-4673-0066-7/12/$26.00©2011 IEEE like gold (Au), silver (Ag) etc. have been used for light trapping purpose in thin flm solar cells [9, 10]. Metal nanoparticles interact strongly with visible and infared photons due to the excitation of localized surface plasmons (LSPs). LSPs are the collective oscillation of fee electron in the metal nanoparticles. The strongest optical interaction occurs at a resonance, with the resonance condition being a fnction of nanopaticles size, shape and type of metal, as well as the local dielectric environment. Upon excitation the LPSs can decay radiatively, resulting in scattering, or non radiatively, resulting in absorption. The resonance scattering peak can be tune by optimizing the size of the particle and by changing surrounding medium. This approach has the potential to confne and guide the incident radiation into the substrate. In this letter, we studied the localized surface plasmon effect of the Au nanoparticles deposited on the SiNH array textured surface for the thin flm solar cells application. II. THEROY AND SIMULAITON MODEL Fig. 1 depicts the schematic of the SiNH arrays textured surface with the periodicity P, diameter D and nanohole depth H for the optical simulation. To include the localized surface plasmon effect, Au nanoparticles are kept on the surface of the SiNH structure. This can be done experimentally by the thermal dewetting of thin gold flms deposited on the SiNH structure as in [ 13]. The plane electromagnetic wave is assumed to be normally incident on the sample. The energy (a) PML H -- j --  P PML (b) Fig. 1. (Color online) Three dimensional structure of SiNH arrays textured surface. (b) Two dimensional unit cell structure of SiNH arrays textured surface with periodicity P, diameter D and nanohole depth H. 000360