Author(s)

Z. P. Ling, J. Ge, R. Stangl, A. G. Aberle, T. Mueller

Solar Energy Research Institute of Singapore, National University of Singapore, Singapore.
Solar Energy Research Institute of Singapore, National University of Singapore, Singapore;Department of Electrical and Computer Engineering, National University of Singapore, Singapore.
Solar Energy Research Institute of Singapore, National University of Singapore, Singapore;National University of Singapore Graduate School for Integrative Sciences and Engineering, Singapore.

Hydrogenated doped silicon thin films deposited using RF (13.56 MHz) PECVD were studied in detail using micro Raman spectroscopy to investigate the impact of doping gas flow, film thickness, and substrate type on the film characteristics. In particular, by deconvoluting the micro Raman spectra into amorphous and crystalline components, qualitative and quantitative information such as bond angle disorder, bond length, film stress, and film crystallinity can be determined. By selecting the optimum doped silicon thin film deposition conditions, and combining our p-doped and n-doped silicon thin films in different heterojunction structures, we demonstrate both (i) an efficient field effect passivation and (ii) further improvement to c-Si/a-Si:H(i) interface defect density with observed improvement in implied open-circuit voltage V_OC and minority carrier lifetimes across all injections levels of interest. In particular, the heterojunction structure (a-Si:H(p)/a-Si:H(i)/c-Si(n)/a-Si:H(i)/a-Si:H(p)) demonstrates a minority carrier lifetime of 2.4 ms at an injection level of 10¹⁵ cm^-3, and a high implied open-circuit voltage of 725 mV. Simulation studies reveal a strong dependence of the interface defect density D_it on the heterojunction silicon wafer solar cell performance, affected by the deposition conditions of the overlying doped silicon thin film layers. Using our films, and a fitted D_it of 5 × 10¹⁰ cm^-2·eV^-1, we demonstrate that a solar cell efficiency of ~22.5% can be potentially achievable.

Raman Spectroscopy; Heterojunction Silicon Wafer Solar Cells; Doped Silicon; Simulation; Passivation

Ling, Z. , Ge, J. , Stangl, R. , Aberle, A. and Mueller, T. (2013) Detailed Micro Raman Spectroscopy Analysis of Doped Silicon Thin Film Layers and Its Feasibility for Heterojunction Silicon Wafer Solar Cells. Journal of Materials Science and Chemical Engineering, 1, 1-14. doi: 10.4236/msce.2013.15A001.