Improved Separation and Collection of Charge Carriers in Micro-Pyramidal-Structured Silicon/PEDOT:PSS Hybrid Solar Cells

Abstract

Silicon (Si)/organic polymer hybrid solar cells have great potential for becoming cost-effective and efficient energy-harvesting devices. We report herein on the effects of polymer coverage and the rear electrode on the device performance of Si/poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) hybrid solar cells with micro-pyramidal structures. These hybrid solar cells provided adequate generation of charge carriers owing to the suppression of reflectance to below 13%. Additionally, the separation of the photogenerated charge carriers at the micro-pyramidal-structured Si/PEDOT:PSS interface regions and their collection at the electrodes were dramatically improved by tuning the adhesion areas of the PEDOT:PSS layer and the rear electrode materials, thereby attaining a power conversion efficiency of 8.25%. These findings suggest that it is important to control the PEDOT:PSS coverage and to optimize the rear electrode materials in order to achieve highly efficient separation of the charge carriers and their effective collection in micro-textured hybrid solar cells.

Configuration Effect of Antireflection Layer on Photovoltaic Performance of Silicon/PEDOT:PSS Hybrid Solar Cells

“…For the Si substrate with such micro-textured surfaces, the PEDOT:PSS layer, which is a p-type-like conjugated conducting polymer, was spin-coated at a spin speed of 7500 rpm. We have previously confirmed that for micro-pyramidal structures [11] and nanowire array structures [19] this spin speed enables the PEDOT:PSS layer to better adhere on micro-textured surfaces. The morphology of the PEDOT:PSS layer on the micro-desert textured surfaces and honeycomb surfaces was analyzed by means of cross-sectional SEM micrographs, as shown in Figures 2a and 2b, respectively.…”

“…The reduced reflectance of the hybrid solar cells that had the micro-pyramidal surfaces significantly contributed to the increased PCE value of 8.25%, in comparison to the PCE value of 1.72% of planar hybrid solar cells [11] . Therefore, the construction of an optimal textured configuration can induce conditions conducive to the enhancement of antireflection capabilities and PCE values.…”

“…A textured configuration can provide potentially effective tools for reducing reflectance, which is closely related to the generation rate of charge carriers in hybrid solar cells, and also to their corresponding photovoltaic performance. As a matter of fact, we have previously proved that a micro-pyramidal-structured Si surface, which is a widely used texture configuration, is effective in reducing the reflectance to a value of 21 -28% in the incident wavelength range of 500 -1000 nm, compared to a planar Si surface, which has a reflectance of 33 -40% [11] .…”

High Performance of PEDOT:PSS/n-Si Solar Cells Based on Textured Surface with AgNWs Electrodes

“…At a low rate, the surface tension of the PEDOT:PSS solution makes it hard to penetrate into the valleys surrounded by pyramids. The increasing spin-coating rate could enhance the penetration rate and the adhesiveness of PEDOT:PSS solution on the micro-pyramidal surface [ 26 ]. The coverage area is expanded with spin-coating rate; the voids become so small that the PEDOT:PSS could nearly conformal contact with the textured substrates.…”

“…As shown in Fig. 5 , the contact junction areas between PEDOT:PSS film and the top of pyramids are so small that PEDOT:PSS film cannot collect enough charge, resulting in a poor heterojunction [ 26 , 27 ]. In addition, due to the wide bandgap of PEDOT:PSS, PEDOT:PSS film could reduce the interface recombination velocities and block electrons from recombination at the front surface of device.…”