Stretched-exponential increase in the open-circuit voltage induced by thermal annealing of amorphous silicon-carbide heterojunction solar cells

Abstract

In this letter, the annealing behavior of the open-circuit voltage improvement of n-doped amorphous silicon-carbide heterojunction solar cells is investigated in detail. We present our results of a significant open-circuit voltage improvement of more than 100 mV up to a maximum value of 675.5 mV triggered by thermal annealing on a hotplate. The observed open-circuit voltage behavior can be described very well by a stretched-exponential function, which in general describes relaxation rates in complex systems. Therefore, we suggest a diffusion of weakly bonded hydrogen, activated by the annealing, which saturates dangling bonds in the amorphous layer itself and at the heterojunction interface, to be responsible for the strong Voc improvement.