Abstract
Integration of light-trapping features and exploitation of metal nanostructure plasmonic effects are promising approaches for enhancing the power conversion efficiency of organic solar cells. These approaches’ effects on the light absorption enhancement have been widely studied, especially in inorganic devices. While this light-trapping concept can be transferred to organic devices, one has to also consider nanostructure-induced electrical effects on the device performance, due to the fundamental difference in the organic semiconducting material properties compared to their inorganic counterparts. In this contribution, we exemplarily model the electrical properties of organic solar cells with rectangular-grating structures, as compared to planar reference devices. Based on our numeric results, we demonstrate that, beyond an optical absorption enhancement, the device fill factor improves significantly by introducing the grating structures. From the simulations we conclude that enhanced carrier collection efficiency is the main reason for the increased solar cell fill factor. This work contributes towards a more fundamental understanding of the effect of nanostructured electrodes on the electrical properties of organic solar cells.
Highlights
Low material and fabrication cost, the ease of processing organic materials and the possibility of making ultra-thin, flexible cells using techniques, such as solution processes[1, 2], printing[3, 4] and roll-to-roll technology[5], render organic solar cells (OSCs) ideal candidates for the future renewable energy market
We find a significant improvement of the electrical properties in the investigated nanostructured organic solar cell, beyond what is governed by the optical absorption enhancements, originating merely from the implemented grating structure
The exemplary chosen conventional OSC structure studied in this work is composed of the following well-known multilayer structure (Fig. 1): Indium thin oxide (ITO)/poly-3,4-ethylenedioxythiophene:poly(styrenesulfonate) (PEDOT:PSS) /Poly(3-hexylthiophene-2,5-diyl)(P3HT) blended with [6,6]-phenyl C61 butyric acid methyl ester(PC60BM)/Aluminum(Al)
Summary
Low material and fabrication cost, the ease of processing organic materials and the possibility of making ultra-thin, flexible cells using techniques, such as solution processes[1, 2], printing[3, 4] and roll-to-roll technology[5], render organic solar cells (OSCs) ideal candidates for the future renewable energy market. Organic photoactive materials come with certain inherent drawbacks such as a relatively narrow absorption band, short exciton diffusion lengths and low charge carrier mobility[14]. To meet these drawbacks and to further increase the device efficiency, various light management techniques have been investigated to achieve optical field enhancement in the photoactive layer region. The integrated light-trapping nanostructures are likely to affect physical processes such as charge carrier losses, transport and collection efficiency These processes depend on several factors, such as the electric field distribution, the exciton separation process and the spatial concentration dependence of carrier recombination, effectively influencing the final PCE of the cell
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