Interface Modification by Ion Implantation and Optical Characterization of High-efficiency Cu(In,Ga)Se_1tn2 Solar Cells PDF Download

Author: Jakob Haarstrich
Publisher:
ISBN:
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Languages : en
Pages : 194

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Book Description

Author: Jakob Haarstrich
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Book Description
Three different issues are discussed in this thesis, which aim for a deeper understanding of Cu(In,Ga)Se2 material properties and solar cell functionality: (1)Near-surface ion implantation in Cu(In,Ga)Se2 absorber layers is studied as a method for the fabrication of buffer-free solar cells. Simulations show the beneficial effect of an n-type surface layer (buried junction). To obtain an inversion by means of ion implantation, an annealing procedure is developed that avoids annealing-induced degradation of the cell, minimizes the diffusion of the ions, and recovers the implantation damage. Buffer-free solar cells made from implanted absorbers show strongly improved diode characteristics comparable to the ones of cells with a CdS buffer and a maximum efficiency of 10.2% (11.2% active area). (2)A model is developed for the application of luminescence techniques on band-gap graded semiconductor thin-films. Several DA-emissions are detected in the cathodoluminescence (CL) and photoluminescence (PL) spectra of Ga-graded in Cu(In,Ga)Se2 and related to the local Ga-contents in the layer. The depth-distribution of the luminescence signal is correlated to the band-gap profile. Drift of excited charge carriers towards the band-gap minimum is caused by the grading-induced quasi-electric field, which must be considered when explaining the spectra obtained in plan-view measurements. Monochromatic CL imaging on cross-sections is capable to determine the minority carrier mobility.