Low-temperature synthesis TiOx passivation layer for organic-silicon heterojunction solar cell with a high open-circuit voltage

Organic/silicon (Si) heterojunction solar cells may promise for high performance and low cost solar cell manufacture because they can combine advantages of Si and organic semiconductors. However, the performances of organic-Si solar cells were still mainly jeopardized by Si rear contact recombination losses. Here, titanium oxide (TiOx) layer via low-temperature solution synthesis way was deposited on Si rear side to reduce electrical losses. Minority carrier lifetime, transient photovoltage decay and external quantum efficiency measurements indicated that TiOx could effectively suppress the recombination losses of Si rear side, which reflected in the improvement of open circuit voltage (Voc) and long-wavelength photoresponse. Contact resistance and capacitance-voltage measurements further showed that resistance and rear adverse barrier height (Phi(-)) between Si and aluminum could be dramatically reduced. A power conversion efficiency (PCE) of 14.3% was achieved for textured Si/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT: PSS) solar cell by incorporating TiOx layer between Si and aluminum. A V-oc of 643 mV was achieved based on this low-temperature processed organic-Si heterojunction solar cell. The outstanding performance was ascribed to Si-O-Ti bonding at TiOx/Si interface, which was identified by X-ray photoelectron spectroscopy. This simple low-temperature solution processed metal oxide layer provided a facile way for Si surface passivation to achieve high performance solar cells.