Rear emitter silicon heterojunction solar cells. Fewer restictions on the optoelectrical properties of front side TCOs

A simple and straightforward approach to lower the influence of the ohmic and non-generation losses caused by the lateral carrier transport within the front side TCO on the efficiency of monofacial SHJ cells is discussed. It is shown by 2D numerical device simulations for a high, medium and low mobility TCO that by simply flipping the emitter from the front-side to the rear-side the lateral carrier collection at the grid electrode can be improved. An additional lateral transport path via the absorber leads to the fact that the effective Rsheet of the front can be lower than the actual Rsheet of the applied TCO. In conclusion, fewer restrictions for the choice of the front side TCO and the design of the front side metal grid electrode are observed. Depending on the optimization route, this allows for higher efficiencies or the application of more economical TCOs.