Ultra-thin CIGS: 2D Modelling and impactful results for optimal cell design and characterizations

We present a 2D model of an Al
₂
O
₃
-passivated ultrathin Cu(In, Ga)Se
₂
photovoltaic cell with rear-contact pattern. Simulation results follow the experimental trends, highlighting the significant effects of the passivation quality and of the Mo/CIGS contact resistance. Improvements in Jsc and Voc are discussed for different sizes of openings, relative to an excellent passivation quality (i.e. high density of negative charges in the passivation layer). However, a degradation is predicted for a poor passivation (i.e. low density of such charges) or a high contact resistance. We point out an optimum in efficiency when varying the opening widths at fixed hole-pitch and fixed contact resistance for a width to pitch ratio around 0.2. These simulation results provide significant insights for optimal cell design and characterizations of passivated UT-CIGS PV cells.