Studies Of Cadmium Free Buffer Layers ZnS Thin Films Of Cu(In, Ga)Se₂-based Solar Cell

The Cu(In,Ga)Se₂(CIGS)-based solar cell belongs to theâ… -â…¢-â…¥class of thin film solar cells,which are prepared routinely on glass and other low-cost substrates. Because of its low material cost,potential scalability,and efficiencies competitive with the presently predominant crystalline-Si technology.It has shown great promise for photovoltaic applications.Nowadays,CdS has been usually used for a buffer layer of heterojunction solar cells.However,there are the losses introduced by the CdS layer in the UV range. Furthermore,CdS is carcinogenic to humans.Because of environmental issues and the losses introduced by the CdS layer in the UV range which limit the level of the optimal performances of the cells,the preparation of cadmium free buffer layers is one of the major objectives in the field of CIGS solar cells.This research has led to the investigation of ZnS as a buffer layer in ZnO/ZnS/CIGS devices.Zinc and cadmium sulphides are compound semiconductors.These materials have many similarities,both exist in cubic hexagonal and polytypical forms and are wide, direct bandgap semiconductors.ZnS is an n-type semiconductor with a wider band gap(3.7eV).Furthermore,its constituent elements are nontoxic to the human body, and are very cheap and abundant.Therefore,ZnS is very suitable for a buffer layer of heterojunction solar cells.However,there are relatively few reports of successful fabrication of heterojunction solar cells with a ZnS buffer layer.In our project,I prepared high quality ZnS thin film by a modified chemical bath deposition technique and studied the structure,surface morphology and optical properties.Meanwhile, during the preparation of ZnS thin films by changing the reaction conditions we can get the ZnO thin films with different suface morphology and analyse the surface morphology and structure of ZnO thin films.