Degradation and Accelerated Recovery of Surface Passivation in n+, p+, and Intrinsic Poly‐Si/SiOx Passivating Contacts for Silicon Solar Cells

We report on the degradation and recovery of surface passivation of fired poly ‐Si/SiO x passivating contacts with hydrogen containing Al 2 O 3 during annealing in the dark and under illumination. Upon firing to a peak temperature of 670°C, the iV oc for symmetric test structures with n + , p + , and intrinsic poly ‐Si/SiO x contacts decreases due to a loss of surface passivation. Upon further annealing over the temperature range of 200–350°C in the dark, depending on the type of doping, the surface passivation either shows further degradation followed by recovery, or direct recovery to the initial iV oc . Annealing at higher temperatures and/or higher illumination intensities accelerates the kinetics for both degradation and recovery processes. We show that the degradation and recovery processes are thermally activated and proceed identically in subsequent firing and annealing steps showing their cyclic nature. We present a series reaction model to explain the kinetics of degradation and recovery processes for n + and intrinsic poly ‐Si/SiO x contacts. By fitting the model's rate expressions to the data, the determined effective activation energy barriers for degradation and recovery for n + poly ‐Si/SiO x contacts in the dark are 1.24 and 1.51 eV, which are lowered under 7.5 Suns illumination to 0.76 and 1.15 eV, respectively.