The fundamental operation mechanisms determing the performance of tunnel recombination junctions revealed by a structural study using four different multijunction pv device architectures

Abstract

Tandem photovoltaic (PV) devices are receiving a lot of attention as the next step in PV for further increasing performance in combination with reducing the cost price per Watt peak. The integration of an effective tunnel recombination junction (TRJ) is crucial for efficient multijunction performance. In this work a rigorous and extensive study is presented that reveals the fundamental operating mechanisms that govern the TRJ performance. This is achieved by performing a structural study on the TRJ design in multiple tandem architectures based on different photovoltaic absorber layers. Experimental results are presented of a large number of tandem devices, including SHJ/nc-Si:H, nc-Si:H/a-Si:H, nc-Si:H/a-SiGe:H and a-SiGe:H/a-Si:H, in which the same p-layer design variations are applied. Across these device architectures the influence of the p-layer material properties, p-layer thickness, bilayer configurations and p-doped contact layer properties are investigated, to yield a unique insight into TRJ behavior.