Time Resolved Photoluminescence Imaging Systems And Methods For Photovoltaic Cell Inspection

Abstract

A time-resolved photoluminescence technique is disclosed to image photovoltaic cells and wafers. The effective lifetime is measured directly using a photodetector that has a fast response. A pulsed light source flashes the wafer, generating excess carriers in the silicon. The rate of carrier recombination is monitored by imaging the photoluminescence decay over time. An effective lifetime can be extracted from the photoluminescence decay curve, which can be used to determine the quality of the photovoltaic cells and wafers.

Description

[0001] Cross references to related patent applications [0002] This application claims priority to Provisional Application No. 61 / 318738, filed March 29, 2010, the disclosure of which is hereby incorporated by reference in its entirety. technical field [0003] The subject invention relates to time resolved photoluminescence imaging systems and methods of photovoltaic cell inspection. Background technique [0004] Photoluminescence is the re-emission of light following absorption of higher energy (shorter wavelength) light. Visible light from solar lamps, lasers or LEDs excites electrons in photovoltaic wafer materials such as silicon. Most of the photogenerated electrons give their energy in the form of heat, but a small fraction recombine with holes in the silicon, emitting photons (radiative recombination). More defects in silicon result in more energy being lost as heat and fewer photons are emitted, while fewer defects in silicon result in more radiative recombinatio...

AI Technical Summary

Problems solved by technology

[0007] Existing steady-state photoluminescent signaling techniques are disadvantageous because they require calibration to convert the signal into an effective lifetime

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