Effect of microstructure on the photoactivity of thin film CdSe

CdSe is increasingly being used as a Se source in CdSeTe/CdTe photovoltaic device fabrication. In this paper, a CdSe thin film has been deposited by sputtering These films have then been subject to a CdCl2 activation treatment. The as deposited and treated films have then been characterized with XRD, EBSD, TEM, EDX and PL to analyse the relationship between photoactivity and the microstructural changes that occur during CdCl2 activation. The as deposited CdSe is photo-inactive, the structure is columnar and is a heavily faulted mix of cubic and hexagonal. Cross-sectional TEM reveals a high density of stacking faults. After the CdCl2 treatment, CdSe is photoactive and the microstructure is clearly hexagonal and indexes well in EBSD. The stacking faults are removed. It is important that thin film CdSe at the front of the device is photoactive. It must be fully exposed to the cadmium chloride process and recrystallized if its use as a source of Se in devices is to be successful. Untreated CdSe will have a detrimental effect on device performance