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