Tunable Hole-Selective Transport by Solution-Processed MoO3-x Via Doping for p-Type Crystalline Silicon Solar Cells

Molybdenum oxide (MoO3-x, x < 3) has been successfully used as an efficient hole-selective contact material for crystalline silicon heterojunction solar cells. The carrier transport capability strongly depends on its work function, that is, oxygen vacancies; however, there are lack of effective methods to modulate the multiple oxidation states. Herein, the oxidation states of solution-processed MoO3-x by doping Nb5+ to improve its hole-selective contact performance with silicon are tuned. With the optimum doping concentration of 5%, both the reduced Mo5+ and oxygen vacancies increase, resulting in a decrease in the contact resistivity between the MoO3-x film and p-type silicon from 161.1 to 62.9 m omega center dot cm(2) and an increase of the effective carrier lifetime from 165.4 to 391.0 mu s simultaneously. Similarly, the doping of Ta5+ or V5+ in MoO3-x improves the passivated contact performance with silicon, while the former increases the concentration of oxygen vacancies and the latter reduces it. The solar cell with the structure of Ag/MoO3-x:Nb/p-Si exhibits a conversion efficiency of 18.37%, which is the highest so far reported for the solution-processed MoO3-x/silicon heterojunction. This work demonstrates a feasible strategy of tuning hole selectivity in MoO3-x by doping for high-efficiency solar cells and other optoelectronic device applications.