Process development for back contact power silicon solar cells with emitter wrap through design

Abstract

The combination of the semitransparent monofacial POWER (POlycrystalline Wafer Engineering Result) silicon solar cell concept [1] with the back contact silicon solar cell concept with EWT (Emitter Wrap Through) design [2,3] has led to the first realization of the POWER-EWT cell concept. This cell concept connects the advantages of the POWER cell design with those of the EWT solar cell design. This includes the semitransparency and mechanically flexibility characterizing POWER cells as well as the simplified cell interconnection, the avoidance of shading losses and the uniform appearance constituting the key features of EWT cells. Many processing sequences have been developed. But two of them PV2 and PV5, one relatively simple (PV2) and one with selective emitter design (PV5) were realized with promising results. The highest cell efficiency achieved so far was 8.3%. The characterization of these cells were carried out applying LBIC (Light Beam Induced Current) and thermography measurements besides the standard methods.