Pico-second pulse electron irradiation damage studies in crystalline silicon solar cells

Abstract

This study investigates the effects of picosecond electron irradiation on the performance parameters of commercial crystalline silicon solar cells fabricated using Passivated Emitter and Rear Contact (PERC) solar technology. The irradiation was performed using electrons with energies up to 3.6 MeV, a pulse current density of j_pulse = 200 A/cm², and a fluence of 5.4 × 10¹³ e/cm². Under these conditions the induced radiation defects are predominantly stable cluster-type defects, which is a result of the high electron beam peak intensity. The degradation of the silicon solar cells caused decrease of its parameters, such as the maximum power by more than 40 %. This phenomenon occurs at an electron irradiation fluence more than two orders of magnitude lower than previously reported in the literature for the same effect.

We propose a hypothesis to explain the open circuit voltage (V_OC) behavior in irradiated silicon solar cells. Thus, in irradiated solar cells, charge layers are created within the insulator and at the semiconductor-insulator and/or semiconductor-metal interface, which creates electric field - directed oppositely to the field from the p-n junction. It has been shown that the electric field from these charged layers plays a significant role in reducing V_OC in irradiated solar cells. We suggest that if a controlled charged layer could be created in a solar cell, the electric field direction from which is the same as that of the field from the p-n junction, then the V_OC could be increased, thus enhancing the efficiency of the solar cells.