Intense Pulsed Light Sintering of Electrodeposited CdS Thin Films

In order to manufacture market competitive solar cells, material processing methods with low capital and running costs are required. One method for achieving this goal would be to use atmospheric processing techniques with a high throughput. Here, we report the use of intense pulsed light (IPL) to process cadmium sulfide (CdS) thin films. IPL is an ultra-fast and facile technique for the heat treatment of materials. Pulses of light from the UV to IR wavelengths are absorbed by the material, leading to localized heating and sintering. IPL has been used to successfully make Ag and Cu electrical contacts for use in electronic circuits, however little work exists on the use of IPL in the processing of semiconductor materials. CdS was selected due to its importance in solar cell manufacturing. This n-type semiconductor has been used as a "window" material in high efficiency CdTe and Cu In(1-x)GaxSe2-based solar cells. The effect of energy input and the energy density of the pulse on the films optical, compositional and morphological properties of the films was investigated using UV-Vis spectroscopy, XRD, and SEM. IPL sintering resulted in significant improvement to the CdS crystallinity with processing times <2 mins.