Rahul Dewan - Jacobs University

Contents
Contents
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1 Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Outline of the Thesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 Fundamental Concepts 5
2.1 Characteristic Parameters of Solar Cells . . . . . . . . . . . . . . . . . . . 5
2.1.1 Shockley-Queisser Efficiency Limit . . . . . . . . . . . . . . . . . 7
2.2 Thin-film silicon solar cells . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3 Solar Cell Material Properties . . . . . . . . . . . . . . . . . . . . . . . . 18
2.3.1 Optical Properties of a-Si:H and µc-Si:H . . . . . . . . . . . . . . 19
2.3.2 Optical Properties of ZnO:Al . . . . . . . . . . . . . . . . . . . . . 20
2.4 Light Confinement in Thin-film Silicon Solar Cells . . . . . . . . . . . . . 22
2.4.1 Light Trapping Limits . . . . . . . . . . . . . . . . . . . . . . . . . 25
3 Computational Modeling of Optical Wave Propagation 29
3.1 Optics in Textured Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.2 Review of Electromagnetics Theory . . . . . . . . . . . . . . . . . . . . . 31
3.3 Maxwell’s Equations Solver . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.3.1 Finite Difference Time Domain Method . . . . . . . . . . . . . . . 36
3.3.2 Rigorous Coupled-Wave Analysis . . . . . . . . . . . . . . . . . . 40
4 µc-Si Solar Cells with Integrated Lamellar Gratings 43
4.1 Optical Simulation Model . . . . . . . . . . . . . . . . . . . . . . . . . . 43
4.2 Solar Cells on Smooth Substrates . . . . . . . . . . . . . . . . . . . . . . 45
4.3 Solar Cells with Integrated Gratings Couplers . . . . . . . . . . . . . . . 47
4.3.1 Influence of Grating Height on the Absorption in Solar Cells . . . 48
4.3.2 Influence of Grating Dimensions on the Short Circuit Current . . 53
4.3.3 Comparison of Optical Simulations and Experimental Results . . . 56
4.4 Toward an Optimal Grating Structure . . . . . . . . . . . . . . . . . . . . 57
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