Polysilicon-based tunnel junction Si solar cells with machine learning for tandem cell applications

Abstract

Tandem solar cells are a key technology to exceed the theoretical efficiency limit of single-junction cells. One of the most promising combinations is the silicon-perovskite tandem cells, considering their potential for high efficiency, large-area fabrication, and low cost. Whereas most research focuses on improvements in each subcell, another key challenge relies on the tunnel junction that connects subcells and affects overall cell characteristics. Here, the first demonstration of tunnel junctions using a stack of p/n polysilicon deposited directly on the passivating tunnel oxide are shown to overcome the drawbacks of conventional metal oxide-based tunnel junctions including low tunneling efficiency and sputter damage. Furthermore, using Random Forest analysis, high implied open circuit voltages over 700 mV in the bottom cell with the polysilicon tunnel junction are achieved. Their contact resistivities are as low as 500 mΩ·cm, suggesting FF losses of less than 1 %abs for the operating conditions of a tandem cell.