CIGS and Micromorph Solar Cell Simulation
Date Issued
2010
Date
2010
Author(s)
Huang, Chien-Yao
Abstract
In this thesis, the physics of CIGS and micromorph solar cells are investigated by numerical simulation. At first, simulation models are established and compared with experiment results. Then some issues of high efficiency thin film solar cell are discussed.
Among several thin film solar cells, CIGS solar cell has a record efficiency ~20%, but the progress has largely been driven by empirical optimization rather than by in-depth understanding of appropriate physical models. Therefore, some critical issues for achieving high conversion efficiency are discussed including(1) optimum single band gap of CIGS solar cell and the effects of CBO between CdS/CIGS layers; (2) effects of Ga-grading on CIGS solar cell; (3) effects of junction properties on CIGS solar cell. These simulation results give some insights to achieving high cell efficiency.
Micromorph solar cell has a stack tandem structure and consists of an amorphous silicon top cell and a microcrystalline silicon bottom cell. The interconnection between top and bottom cells is via Esaki tunnel diode. The simulated J-V curve has an S-shape and 33.4 A/cm2 maximum tunnel current Jpeak, which is much greater than photo-generated current Jphoto to prevent distorted J-V curve. The optimal thickness of absorber layer is also discussed and indicates the efficiency of micromorph solar cell is sensitive to current matching. Furthermore, the EQE responses of subcells under different voltage bias are studied by simulation. The different behaviors of top and bottom cell are discussed and referred to difference of optical generation distribution. Finally, surface texture is considered into simulation model and optimizes the texture size. The optimal texture size gives a 2% efficiency improvement than planar structure.
Subjects
CIGS
Micromorph
thin film solar cell simulation
Type
thesis
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