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Graduate Student Seminar - 04/21/2017

"Imaging the Effect of CdSe Window Layers in CdTe Photovoltaics"

by John Howard

Friday, April 21, 2017 -- 12:00 p.m.
Large Conference Room, 1207 Energy Research Facility

Advisor:  Asst. Prof. Marina Leite

Photovoltaic (PV) energy conversion has become an important solution towards the mitigation of anthropogenic global warming. CdTe solar cells possess an inherent cost advantage over competitors due to the relative simplicity of their fabrication. The various types of grain boundaries inherent to CdTe devices do not affect performance in the same manner, making functional imaging techniques with high-resolution essential to determine key electro-structural properties that will inform the design and fabrication of future devices. Here we present a quantitative comparison of two CdTe PV devices with CdSe and CdS window layers. Through the use of scanning photocurrent microscopy, we measure the electrical response of the samples with sub-micron spatial resolution. By spectrally resolving the photocurrent we demonstrate the NIR enhancement in carrier collection by the CdSe sample, where we find that the CdSe window provides a peak in the EQE response of the device in the 830 – 900 nm range, compared to a modest performance for the CdTe solar cells with the standard CdS window layer. Our results indicate that the performance improvement greatly exceeds the variance in photocurrent due to grain boundaries and interfaces.

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