Micron-resolution photocurrent of CdTe solar cells using multiple wavelengths

摘要

An apparatus developed recently at Colorado State University utilizes a diffraction-limited optics system and a high-resolution translation system to measure the laser-induced photocurrent at resolutions of 1 μm and equivalent incident laser intensities of 1 sun (100 mW/cm{sup}2). Multiple lasers in the 635-830 nm range can be easily selected by changing the fiber-optic connectors. The spot profile and location are unchanged when different lasers are selected. In addition, a laser temperature tuned through the 825-857 nm range allows measurement of local variations in the quantum efficiency near the CdTe band gap, which track intermixing of CdS/CdTe. This capability extends the previous analysis, which includes the separation of series resistance and shunting effects. The effect of post-deposition processing and elevated temperature stress on local variations in electrical and optical parameters, especially using the near-bandgap wavelengths, are examined using a series of samples fabricated at NRFL.