Aspects of bifacial cell efficiency

This paper presents simulation and experimental results on the electrical response of n-PERT (passivated emitter rear totally diffused) solar cells under front and rear illumination. The so-called bifaciality factor, which represents the response to rear illumination compared to front illumination, is an important factor for determining the bifacial efficiency and predicting the annual energy output. This factor increased when the recombination parameters of the back-surface field and the base material were improved. Moreover, we found that the bifaciality factor of n-PERT cells increased strongly with the base resistivity. In simulations we studied the cell response under simultaneous front and rear side illumination. According to our results, the simulated bifacial efficiency agrees very well with the “compensated current” efficiency recently proposed for characterization of bifacial modules. The “compensated current” method therefore seems not only a convenient method for characterization of bifacial modules, but also very well suited for use in energy yield predictions.