Solution-processed molybdenum oxide films by low-temperature annealing for improved silicon surface passivation

Abstract

Crystalline silicon solar cells are developing towards higher conversion efficiency, however, the surface recombination and Auger recombination from heavily doped silicon are the main limit. Some metal oxides are of great interest because of their selective contact performance with crystalline silicon, which can minimize the carrier recombination in the contact area. Especially, due to the high work function of molybdenum oxide (MoOx), the MoOx film can provide excellent hole transport and electron blocking properties for the silicon surface. Here, we have deposited MoOx films on the surface of silicon wafer by spin-coating a copper hydromolybdate solution. The MoOx film can provide superior passivation quality compared to thermal evaporated one, with the τeff of 110.6 μs (Δn = 1015 cm−3) obtained on n-type Czochralski silicon. Moreover, the passivation of MoOx film can be further improved by annealing at low temperature and under reduced atmosphere environment. The dense surface morphology of amorphous films and formation of Si–O–Si bonds by annealing are the main reasons for improved silicon surface passivation. This work demonstrates the feasibility of using solution-processed transition metal oxides as effective and low-cost carrier-selective passivating contacts for silicon photovoltaic devices.