Ricerc@Sapienza

The achievable current in a silicon based heterojunction solar cell is a limit in its conversion efficiency. This drawback depends on the optical band-gap of the sun-lighted amorphous layers, that reduces the light spectrum reaching crystalline silicon absorber. The search for new materials to overcome this hurdle is recently focusing its attention on hydrogenated amorphous silicon oxide (a-SiOx:H), which offers effective crystalline silicon surface passivation and optical band-gap larger than the commonly used hydrogenated amorphous silicon (a-Si:H).

Hole-collecting and buffer layers more transparent than amorphous silicon layers are regarded as one of the possible improvements needed in amorphous/crystalline silicon heterojunctions to help reach the limit efficiency of silicon-based solar cells. Recent studies have demonstrated the suitability of sub-stoichiometric molybdenum oxide (MoOx) as hole-extracting layer in heterojunction solar cells based on n-type crystalline silicon. However, up to now MoOx has mainly been used in combination with amorphous silicon, so limiting its potential as a transparent emitter.