Light Trapping And Absorption Enhancement For High Performance Solar Cells And Infrared Photodetectors

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Title: Light Trapping And Absorption Enhancement For High Performance Solar Cells And Infrared Photodetectors
Author: Chen, Li
Abstract: This dissertation presents the work on light trapping and absorption enhancement in solar cells and infrared photodetectors . Hemispherical microstructure based omni -directional anti reflection (Omni -AR ) coating has been designed and developed for solar cells , based on rigorous coupled -wave analysis (RCWA ) and convective coating process . Omni -AR coating enhances light absorption in solar cells , due to the reduced reflection on the structured solar cell surfaces , and the increased optical path length (OPL ) inside the solar cells . Omni -AR coating has been demonstrated as a cost -effective light trapping approach for different material systems , with very low reflection and high transmission over a large range of incident angles (0 -60 degree ) and over a wide spectral range (400 -1000nm ) . Omni -AR coating has also been applied on commercial solar cells based on the cost -effective solution techniques . With omni -AR coating , we obtained increased short circuit current , and increased conversion efficiency , in both organic solar cells and amorphous silicon solar cells . Significant infrared absorption enhancement can also be achieved in photonic crystals (PC ) cavities . In 1D PC structures , the ratio of absorption enhancement to suppression at the photonic bandedge can be as high as 40 . The absolute infrared absorption can be tuned and enhanced by more than 90 % in both the defect cavity and the resonance cavity 1D PC structures . In 2D photonic crystals slab (PCS ) cavities , the absorption enhancement factor is more than 6000 under lateral light stimulation . With vertical light stimulation , the enhancement factor is about 100 . Enhanced infrared absorption can also be obtained through Fano resonance based PC structures . The light is effectively coupled between the in -plane discrete resonance modes and the vertical continuum radiation modes . Based on this principle , 2D PC patterned silicon nanomembrane (SiNM ) Fano filters are fabricated and transferred onto transparent substrates . This type of ultra compact SiNM Fano filters demonstrates strong angular and polarization dependent transmission properties . More significantly , enhanced absorption is achieved via the incorporation of the spectrally aligned colloidal quantum dots (CQDs ) into the air holes of Fano filters . Finally , we propose two kinds of spectrally -selective photodetector structures , based on Fano resonance filters .
URI: http : / /hdl .handle .net /10106 /4898
Date: 2010-07-19

Citation

Light Trapping And Absorption Enhancement For High Performance Solar Cells And Infrared Photodetectors. Available electronically from http : / /hdl .handle .net /10106 /4898 .

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