Stability and degradation mechanisms in pristine single- and double-layer graphene/n-Si Schottky junction solar cells

Abstract We systematically investigated the long-term stability and underlying degradation mechanisms of pristine graphene/n-Si Schottky junction solar cells (GSSCs) by directly comparing single-layer (SL) and double-layer (DL) configurations without encapsulation. Over 70 d under atmospheric conditions, the SL devices exhibited a pronounced power conversion efficiency drop from 5.53% to 4.40%. Conversely, the DL GSSCs demonstrated remarkable stability, maintaining a steady efficiency of approximately 4.8%. Through dark current density–voltage and transient photovoltage (TPV) analyses, we identified that the degradation in SL GSSCs is primarily driven by a substantial increase in series resistance—which doubled from 5.6 to 11.0 Ω cm 2 —rather than the deterioration of the Schottky junction itself. Its stability is evidenced by the highly consistent ideality factors (ranging from 1.01 to 1.13) and TPV relaxation responses for both configurations. These findings challenge the conventional assumption that interfacial degradation dictates device failure, providing a pathway for long-lasting graphene-based optoelectronic devices.