ALD NiO Thin Films As a Hole Transport-Electron Blocking Layer Material for Photo-Detector and Solar Cell Devices
In this report, we demonstrated the usefulness of ALD NiO thin films as HT-EBL/optical material by using it in very thin CdTe solar cells with a superstrate configuration. The CdTe cells were fabricated on a soda-lime glass substrate, and configured with layers of 200nm of SnO2:F/ 50 nm CdS/ 500nm CdTe/4nm Cu and 20nm Au. In test samples, a 3nm thick ALD NiO layer was deposited on the CdTe layer before the Cu/Au deposition. The resulting test and control cells were characterized under AM 1.5G (100mW/cm2) spectrum. The results of the device performance are summarized in Table 1. As may be noted, the CdTe cells with the ALD NiO layer on the anode showed better Voc and FF, and resulted in 15% higher power conversion efficiency (PCE) than that of the control cells. The enhancement of the Voc and FF were ascribed to the enhanced control of the photo-generated carriers. It remains to be determined if the reduction of. Jsc in the test samples is due to optically non-optimized NiO thickness and therefore reflection loss at the back contact or to non-optimized hole collection at the back contact.
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