Fabrication And Investigation Of Silicon/Organic Hybrid Solar Cells

Organic/silicon hybrid solar cells have recently been recognized to be one of potentially low-cost candidates for photovoltaic application, which avoid a high temperature diffusion or implantation process of traditional solar cells to reduce the cost of fabrication. This paper focuses on the investigation of photovoltaic characterization and charge carrier transportation mechanism of silicon nanowires (SiNWs)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOTrPSS) hybrid solar cell. We obtained the best power conversion efficiency (PCE) of 13.1% by optimizing the morphology of SiNWs. Moreover, we explored the application of amorphous silicon in hybrid solar cell as a passivation film. The main work includes:(1) A high PCE of 11.3% was obtained from the silicon/PEDOT:PSS hybrid solar cell by optimizing the fabrication condition. Various methods were used to explore the carrier transport mechanism, (a) The capacitance-voltage characteristics show that a built-in potential of 0.8 eV exists at the interface of silicon/PEDOT:PSS, indicating the formation of an inversion layer, (b) The temperature-dependent dark current density-voltage characteristics suggest that the carrier transportation in the silicon/PEDOT:PSS solar cells is determined by the minority carrier diffusion mechanism, similar to a p-n junction. The majority carrier thermal emission model of Shottky junction was ruled out by combining the capacitance-voltage measurements, (c) The evolution of the carrier lifetime with applied voltage also verifies the formation of strong inversion layer.(2) The different morphologies of SiNWs have an effect on the performance of SiNWs/PEDOT:PSS hybrid solar cell. A high PCE of 12.0% was gained for the hybrid solar cell by optimizing the morphology of SiNWs based on metal-assisted chemical etching. By tailoring the diameters of silicon nanowires (SiNWs) using thermal oxidation treatment followed by hydrofluoric acid etching, a highest PCE of 13.1% is achieved for the SiNWs/PEDOT:PSS solar cells. It is clarified that the high efficiency of hybrid solar cell is strongly associated with the passivation effect of PEDOT:PSS for silicon surface.(3) The amorphous silicon can effectively suppress the interface carrier recombination evidenced by the significant improvement of the carrier lifetime from 21.0 μs to 57.5 μs. The PCE of 4.45%,5.61% were gained for double-side passivated and single-side passivated hybrid soalr cells, respectively. Hybrid solar cells with back surface of amorphous silicon achieved a 20 mV improvement of open-circuit voltage and a 0.13 eV enhancement of build-in potential. However, the PCE of hybrid solar cell based on the amorphorus silicon passivation was declined to 6.65%, due to a decrease of carrier collection efficiency.