Liquid phase crystallized silicon – A holistic absorber quality assessment

Abstract

In this paper, we report on the current status of absorber attributes in Liquid Phase Crystallized Silicon (LPC-Si) cells. To this end, an absorber doping series (ND = 2·1016/cm³ to 7·1017/cm³) and an absorber thickness variation (14 and 33µm) are evaluated. Best cells from the batches for these series showed open circuit voltages up to 640mV and fill factors above 70%. It is observed that for state-of-the-art cells, thicknesses over 15µm are not beneficial due to limited diffusion lengths. Lower absorber doping concentrations tend to yield longer intra-grain diffusion lengths (Ldiff) and better passivated grain boundaries, which may be due to lower impurity precipitation. The longer Ldiff leads to higher short circuit current densities which over-compensate a decrease in open circuit voltage and fill factor with regards to efficiency. Both front and rear surfaces are sufficiently passivated and at the current status the bulk lifetime has most potential for improvement.