Light trapping in Si thin film solar cell

Hamed Ahmadpanahi

Research output: ThesisDissertation (TU Delft)

41 Downloads (Pure)


This thesis is structured in six distinct chapters. In Chapter 1 a general introduction is given to address the main challenge in thin-film silicon solar cells and to motivate the need for light trapping. This chapter also describes the main focus of this thesis and the urge to understand the light behaviour inside a periodic waveguide thin film. This is followed by Chapter 2, which provides the mathematical background and the frame work which has been used throughout the thesis. This chapter presents some practical details and calculation techniques which have been used to obtain our result. In Chapter 3, a semi-analytical approach is introduced to calculate the contribution of guided and nonguided resonances to total absorption of a grating waveguide structure under normal incidence. In this approach, we use Fourier expansion to calculate the energy spectral density of the electric field inside the absorber. In this way, the weight of each resonance in total absorption is defined for a large wavelength range for TM and TE polarization. Additionally, the proposed mathematical model is supported by numerical and rigorous calculations, using a software based on the finite element method. This approach is extended for oblique incidence in Chapter 4. In this chapter it is explained howthe variation of tangential and normal components for TM electric field under oblique incidence influences the accuracy of numerical calculation. The correlation between the density of modes and the absorption peaks due to guided mode excitation is also presented in this chapter. Chapter 5 focuses on calculating the maximum absorption enhancement achieved by each type of resonance in a waveguide structure with symmetric and asymmetric gratings. In this chapter a different approach is introduced to count the number of resonances in a grating waveguide structure, at each frequency. Then, temporal coupledmode theory is used to calculate the maximum absorption enhancement for each diffraction order. This approach is extended for a thin film with double-side texturing. Chapter 6 provides the conclusion of the thesis.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Delft University of Technology
  • Isabella, O., Supervisor
  • Zeman, M., Advisor
Thesis sponsors
Award date16 Sep 2019
Publication statusPublished - 2019


  • Light trapping
  • Diffraction and gratings
  • Thin film
  • Solar Cells
  • Absorption enhancement

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