Bansal, Himanshu
(2016)
Enhancement of Optical Absorption in Amorphous Silicon Solar Cells Using Multilayer Nanoparticle Arrays and By Up-Conversion of Light.
Masters thesis, Indian Institute of Technology Hyderabad.
Abstract
Recently, thin-film solar cells enhanced with plasmonic nanoparticles have attracted much attention of the scientific community. To improve the performance of such cells, an optimization of the nanoparticle parameters such as size, surface coverage and material is performed. Also it is found out that lanthanides along with host material can be used for upconversion process which further enhances the absorption efficiency for solar cells. Based on this optimization, the role of surface plasmons and upconversion process is discussed and analyzed with respect to optical absorption of the photoactive layer.
This thesis focuses on the use of lanthanide ions for spectral conversion in solar cells. The main energy loss in the conversion of solar energy to electricity is related to the so-called spectral mismatch: low energy photons are not absorbed by a solar cell while high energy photons are not used efficiently. To reduce the spectral mismatch losses both upconversion and downconversion are viable options. In the case of upconversion two low energy infrared photons that cannot be absorbed by the solar cell, are added up to give one high energy photon that can be absorbed. In the case of downconversion one high energy photon is split into two lower energy photons that can both be absorbed by the solar cell. The rich and unique energy level structure arising from the 4fn inner shell configuration of the trivalent lanthanide ions gives a variety of options for efficient up- and downconversion. Here upconversion process has been used for improving solar cell efficiency.
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