Selectivity issues of MoOx based hole contacts

Evaporated MoOx was investigated as hole contact for silicon solar cells. To improve understanding of the carrier selectivity of metal oxide based hole contacts the J-V characteristic of simple MoOx-based solar cells was evaluated and different pre and post deposition treatments as well as the influence of the buffer layer for solar cell like precursors were investigated. Further on, the loss of selectivity with annealing was investigated with the same set of samples. While characteristic changes of the optical properties by some treatments indicated the modification of the metal oxides gap states, a clear correlation with the electrical junction properties was not observed. Since none of those treatments showed a beneficial influence on carrier selectivity, further work is needed towards an efficient engineering of the selectivity. However, evaluation of various data showed that the loss of selectivity with annealing is governed by a reduced effective work function of the TMOs.