Abstract
Organic/silicon nanowires (SiNWs) hybrid solar cells have recently been recognized as one of potentially low-cost candidates for photovoltaic application. Here, we have controllably prepared a series of uniform silicon nanowires (SiNWs) with various diameters on silicon substrate by metal-assisted chemical etching followed by thermal oxidization, and then fabricated the organic/SiNWs hybrid solar cells with poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS). It is found that the reflective index of SiNWs layer for sunlight depends on the filling ratio of SiNWs. Compared to the SiNWs with the lowest reflectivity (LR-SiNWs), the solar cell based on the SiNWs with low filling ratio (LF-SiNWs) has a higher open-circuit voltage and fill factor. The capacitance-voltage measurements have clarified that the built-in potential barrier at the LF-SiNWs/PEDOT:PSS interface is much larger than that at the LR-SiNWs/PEDOT one, which yields a strong inversion layer generating near the silicon surface. The formation of inversion layer can effectively suppress the carrier recombination, reducing the leakage current of solar cell, and meanwhile transfer the LF-SiNWs/PEDOT:PSS device into a p-n junction. As a result, a highest efficiency of 13.11% is achieved for the LF-SiNWs/PEDOT:PSS solar cell. These results pave a way to the fabrication of high efficiency organic/SiNWs hybrid solar cells.
Highlights
Experimental proceduressilicon nanowires (SiNWs) Preparation. 300 μ m thick, n-type single-side polished 100-oriented crystalline silicon wafers with a resistivity of 0.1–0.3 Ω cm were used for experiments
Organic/silicon nanowires (SiNWs) hybrid solar cells have recently been recognized as one of potentially low-cost candidates for photovoltaic application
It has been reported that an efficiency up to 17.4% has been obtained for the PEDOT:PSS/silicon solar cell based on a back junction[19]
Summary
SiNW Preparation. 300 μ m thick, n-type single-side polished 100-oriented crystalline silicon wafers with a resistivity of 0.1–0.3 Ω cm were used for experiments. The fabrication of uniform SiNWs was based on metal-assisted chemical etching (MACE) of silicon wafers by using Au metal mesh with nanoholes prepared from anodic aluminum oxide (AAO) membranes[21]. The Au mesh was transferred to the silicon substrate after being released from the AAO membrane by floating in 0.1 M NaOH solution for 2 h. A series of SiNWs with different diameters were obtained by annealing the samples in dry oxygen thermal oxidation treatment at 900°C for different times, followed by the immersion in diluted HF acid solution (5 wt%) for 60 s. The improved PEDOT:PSS film was spin-coated on the SiNWs sample with a rate of 3000 r/min, and annealed at 125 °C for 7 min. The EQE spectrum was recorded using a Stanford Research System Model SR830 Lock-in Amplier unit coupled with a monochromator and a 500 W xenon lamp, calibrated by a silicon photodiode with known spectral response
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