Embedding metal electrodes in thick active layers for ITO-free plasmonic organic solar cells with improved performance.

Sangjun Lee,Namkyoo Park,Daniel R Mason,Sungjun In

doi:10.1364/oe.22.0a1145

Sangjun Lee, Namkyoo Park + Show 2 more

Open Access

https://doi.org/10.1364/oe.22.0a1145

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Journal: Optics Express	Publication Date: Jun 10, 2014
Citations: 10	License type: cc-by

Affiliation: Ajou University, Seoul National University

Abstract

We propose and numerically investigate the optical performance of a novel plasmonic organic solar cell with metallic nanowire electrodes embedded within the active layer. A significant improvement (~15%) in optical absorption over both a conventional ITO organic solar cell and a conventional plasmonic organic solar cell with top-loaded metallic grating is predicted in the proposed structure. Optimal positioning of the embedded metal electrodes (EME) is shown to preserve the condition for their strong plasmonic coupling with the metallic back-plane, meanwhile halving the hole path length to the anode which allows for a thicker active layer that increases the optical path length of propagating modes. With a smaller sheet resistance than a typical 100 nm thick ITO film transparent electrode, and an increased optical absorption and hole collection efficiency, our EME scheme could be an excellent alternative to ITO organic solar cells.

Highlights

High optical transparency and large electrical conductivity of top-loaded electrodes in solar cells ensures efficient transmission of light into the active layer and efficient transport of collected charge carriers
Contrary to the CME and indium tin oxide (ITO) reference, the embedded metal electrodes (EME) exhibits an optical absorption that increases monotonically with the active layer thickness owing to its preservation of optimal plasmonic coupling between the electrode array and metallic backplane, at the same time as the optical path length is increased in the thicker active layer
We proposed a new type of plasmonic organic solar cell based on a periodic array of metal nanowire electrodes embedded into an active layer

Summary

Introduction

High optical transparency and large electrical conductivity of top-loaded electrodes in solar cells ensures efficient transmission of light into the active layer and efficient transport of collected charge carriers. Our proposed structure, consisting of a periodic Ag nanowire anode (rectangular element size wAg x dAg) embedded with an index matching SiO2 element (wAg x dSiO2) is denoted ‘embedded metal electrode’ (EME, Fig. 1(b)). As a reference, both CME and EME are compared to a typical ITO-based structure with top-loaded 100 nm thick ITO film (Fig. 1(c)). Contrary to the CME and ITO reference, the EME exhibits an optical absorption that increases monotonically with the active layer thickness owing to its preservation of optimal plasmonic coupling between the electrode array and metallic backplane, at the same time as the optical path length is increased in the thicker active layer. On top of its improved optical performance, our calculations of the EME sheet resistance suggest it as a suitable replacement of ITO as a transparent electrode in organic solar cells

Device architecture and suggested fabrication method

Optical absorption and electrical properties of EME solar cells

Conclusion