Molybdenum Oxide in Hole-selective Contacts for Silicon-based Solar Cells

Abstract

Although front and back contact silicon heterojunction solar cells exhibit promising external parameters, they are limited by the front highly absorptive doped layers. Due to their opto-electronic properties, research and development groups have demonstrated that transition metal oxides (TMO) are potential alternatives for doped layers in solar cells. In particular, molybdenum oxide (MoOx) is a good candidate for the p-contact layers. This thesis presents an investigation of the introduction of MoOx in the front contact of solar cells. To this purpose, the evolution of the passivation is evaluated along the fabrication process together with temperature sensitivity. The application of the layer negatively influences the passivation quality. Moreover, the passivation quality decreases more after annealing and transparent conductive oxide (TCO) deposition. We mitigate such issues by treating the surface of the passivation layer before MoOx application. The optimized contact stack shows implied open-circuit voltage above 715 mV and lifetime 1.57 ms. Finally, the contact stack is implemented in solar cells demonstrators. The best solar cell exhibits a short circuit current density (JSC) equal to 35.64 mA/cm2, an open-circuit voltage (VOC) of 690 mV, a fill factor (FF) of 77.29% and a total efficiency (η) of 19.01%.