13.2% efficiency Si nanowire/PEDOT:PSS hybrid solar cell using a transfer-imprinted Au mesh electrode

Abstract

In recent years, inorganic/organic hybrid solar cell concept has received growing attention for alternative energy solution because of the potential for facile and low-cost fabrication and high efficiency. Here, we report highly efficient hybrid solar cells based on silicon nanowires (SiNWs) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (

Pedot: PSS) using transfer-imprinted metal mesh front electrodes. Such a structure increases the optical absorption and shortens the carrier transport distance, thus, it greatly increases the charge carrier collection efficiency. Compared with hybrid cells formed using indium tin oxide (ITO) electrodes, we find an increase in power conversion efficiency from 5.95% to 13.2%, which is attributed to improvements in both the electrical and optical properties of the Au mesh electrode. Our fabrication strategy for metal mesh electrode is suitable for the large-scale fabrication of flexible transparent electrodes, paving the way towards low-cost, high-efficiency, flexible solar cells.

Figure 1. Metal transfer imprinting.

A schematic illustration of the fabrication process for the mesh electrodes on transparent substrates.

Figure 2. Transfer-imprinted Au mesh electrodes.

(a) A photograph of a red light-emitting diode in operation using an Au mesh electrode. (b) An FESEM image of an Au mesh pattern, with a line-width of 2 μm and pitch of 100 μm. The inset in panel (b) shows a high-magnification SEM image. (c) Transmittance spectra of various Au mesh and ITO electrodes.

Figure 3. SiNW/PEDOT:PSS hybrid solar cell.

An overview of the fabrication process for the SiNW/PEDOT:PSS hybrid solar cells. (a) AgNPs were precipitated using a galvanic displacement reaction. (b) SiNWs were allowed to form at room temperature for 20 s using a mixture of 4.8 M HF and 0.6 M H₂O₂. (c) An Al₂O₃ thin film was deposited using ALD to form a passivation layer. (d) PEDOT:PSS solution was spin coated onto both the SiNW array and the Au mesh electrode. (e) The PEDOT:PSS-coated Au mesh electrode and the SiNW array were directly pressed together and annealed. (f) A resulting SiNW/PEDOT:PSS hybrid solar cell.

Figure 4. SiNW arrays.

(a) The tilted cross-sectional SEM images of the 200-nm-long SiNWs. (b) The corresponding morphology after coating with the PEDOT:PSS solution. (c) A high-resolution TEM image of the Al₂O₃ layer on the crystalline Si sample. (d) Reflectance spectra of the 200 nm-long SiNWs before being coated with PEDOT:PSS, along with the Si wafer.

Figure 5. Photovoltaic properties of the hybrid solar cells.

(a) The J–V characteristics of the hybrid solar cells with various front electrodes under illumination with AM 1.5 G light at 100 mW/cm². (b) The J–V characteristics of the hybrid solar cells in the dark. (c) EQE spectra of the hybrid solar cells with various front electrodes. (d) A summary of the photovoltaic properties of the hybrid solar cells.