Increasing the efficiency of film solar cells based on cadmium telluride

Abstract

We conducted analysis of losses in the output parameters of solar cells based on CdTe/CdS, which are caused by the design features of instrument structure and by the photoelectric processes that occur in its volume when absorbing light. Based on the carried out analysis, the ways for the improvement of SC are determined for the purpose of increasing the efficiency of a photo element. The approaches to increasing the efficiency of a photo element are examined, which were previously realized by scientists. It was established that, despite the implemented technologies, efficiency of the obtained samples does not reach theoretical maximum (ηtheor≈29 %). A basic technological approach, which was realized by many authors, when creating the low ohmic contacts to SC based on CdS/CdTe is the formation of tunnel contacts, using in this case thin films that contain copper or copper chalcogenide. However, the diffusion of copper into the base layer leads to the degradation of output parameters of the film SC based on CdS/CdTe. That is why we carried out comprehensive studies, aimed at designing back contacts to the CdTe base layers for the creation of highly effective, degradation-resistant solar cells.It is experimentally established that in the absence of the copper layer at the back surface or in the absence of the annealing process after the formation of a back contact, efficiency of the film ITO/CdS/CdTe/Cu/Au SC is limited at the level of 3–4 % due to the work of instrument structure in the regime of "open diode". In the course of formation of quality Cu/Au tunnel contact, the SC efficiency increases to 10,4 %.