Solar Energy Materials and Solar Cells, Vol.181, 2-8, 2018
Liquid phase crystallized silicon - A holistic absorber quality assessment
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 (N-D = 2.10(16)/cm(3) to 7.10(17)/cm(3)) and an absorber thickness variation (14 and 33 pm) are evaluated. Best cells from the batches for these series showed open circuit voltages up to 640 mV and fill factors above 70%. It is observed that for state-of-the-art cells, thicknesses over 15 pm are not beneficial due to limited diffusion lengths. Lower absorber doping concentrations tend to yield longer intra-grain diffusion lengths (L-diff) and better passivated grain boundaries, which may be due to lower impurity precipitation. The longer L-diff 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.
Keywords:Liquid Phase Crystallization;Silicon solar cells;Thin-film;Diffusion length;Surface recombination;LBIC