Optical Absorption Enhancement in Silicon Nanohole Arrays for Solar Photovoltaics

Optical Absorption Enhancement in SiliconNanohole Arrays for Solar Photovoltaics Sang Eon Han and Gang Chen* Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 Reporter: Bo-Yu Huang Advisor: Peichen Yu Green Phtonics Lab., National Chiao Tung University 1 2014/11/20

Outline Introduction Nanorod arrays Nanohole arrays Simulation & Discussion Summary

Introduction Poor infrared absorption of crystalline silicon (indirect band gap) 200-300 µm c-Si active layers that absorb light efficiently This thickness accounts for ∼ 40% of the total cost An effective technique for light trapping in thin active layers needs to be developed

Introduction Nanorod arrays Construct a p-n or a p-i-n junction in the radial direction of each nanorod Shorten the carrier diffusion length Anti-reflection

Introduction Nanohole arrays We find that nanohole arrays are comparable to or even better than nanorod arrays in terms of light absorption.

Introduction Applied physics letter, 96, 181903 (2010) Nano letters,10, 1082 (2010) JACS, 132, 6872 (2010) Silicon nanohole arrays exhibit better absorption and mechanical robustness 6

Simulation & Discussion For rod: Filling fraction=

Simulation & Discussion Absorption is higher for the nanohole array when λ is less than approximately 750 nm

Simulation & Discussion thickness is 2.33 µm

Summary We have presented the optical properties of c-Si nanohole array structures and found that their absorption is better than nanorod arrays. Nanohole array structure requiring one-twelfth the c-Si mass and one-sixth the thickness of a standard 300 µm Si wafer.

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Optical Absorption Enhancement in Silicon Nanohole Arrays for Solar Photovoltaics