Accelerated life tests of SnO2—Si heterojunction solar cells

The series resistance of SnO2-Si heterojunction solar cells increases with time on-shelf after fabrication, but tends to stabilize after a few weeks. This degradation is enhanced at elevated temperatures. The open-circuit voltage may increase or decrease with time. It is concluded that the degradation results from the spontaneous growth of a high-resistance interfacial layer (probably SiO2) at the SnO2-Si interface. Degradation proceeds in two steps. The first step is relatively rapid and accounts for the degradation on-shelf. The second step is slower, is observed only at elevated temperatures, and is believed to be limited by the rate of transport of oxygen across the existing SiO2layer. Under prolonged illumination, the series resistance and open-circuit Voltage both decrease, Although the second stage of degradation is too slow to affect the practical life of these cells, it is not clear if the initial rapid stage and/or degradation under illumination will preclude the practical use of these cells.