Broadband Absorption and Efficient Hot-Carrier Photovoltaic Conversion based on Sunlight-induced Non-radiative Decay of Propagating Surface Plasmon Polaritons

Mengzhu Hu,Sailing He,Hao Dai,Liu Yang

doi:10.1038/s41598-017-05399-6

Mengzhu Hu, Sailing He + Show 2 more

Open Access

https://doi.org/10.1038/s41598-017-05399-6

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Abstract

Localized surface plasmon polaritons (SPPs), which can decay non-radiatively into hot carriers, have been widely employed to extend the responses of traditional semiconductor-based photocatalytic and photovoltaic devices to sub-bandgap photons. However, radiative decay is unavoidable and adverse to device performances. Here, we propose to take advantage of propagating SPPs, another form of SPPs, which possess non-radiative decay only. A special gold-titanium dioxide nanowire array with each nanowire capped with a nanocone is proposed. The adjacent nanocones forming top gradual openings attribute to efficient sunlight harvesting, while the neighbouring nanowires forming bottom nanoslots allow sufficient absorption due to the propagating SPPs. With the combined advantages, almost 100% of light is absorbed by a very thin gold film in the visible range, and 73% in the whole considered range of 400–1170 nm, superior to the nanocone cell based on localized SPPs, let alone the nanowire-based and planar counterparts. Therefore, much better photovoltaic conversion performance is achieved with short-circuit current density of 0.74 mA/cm2 and open-circuit voltage of 0.41 V. This work confirms the superiority of non-radiative decay of propagating SPPs to the localized SPPs in terms of generation of hot carriers, providing a promising way of extracting electrons in metal into photocurrent.

Highlights

Resonances, as one form of SPPs, can be tuned by the nanoparticle size
Different plasmonic nanostructures have been developed to generate localized SPPs and enhance their non-radiative decay into hot carriers, e.g., vertical Au nanorod arrays coated with TiO2 for high-efficiency solar water splitting[21] and as a solid-state photovoltaic solar cell[22], large-area Au-TiO2 photonic crystal[23] and Au nanograting on top of silicon[24] for photodetection, etc
It consists of two Au films and in between a TiO2 nanowire array on top of a 100-nm thick TiO2 slab

Summary

Introduction

Resonances, as one form of SPPs, can be tuned by the nanoparticle size. they are always accompanied with radiative decay[28], leading to less efficient light harvesting and lower power conversion efficiency (PCE). In 2015, we proposed a special plasmonic waveguide by coating a silicon ridge waveguide with a thin Au film on its top and sidewalls and achieved greatly enhanced photoresponsivities over a very broad wavelength range from 1.2 to 1.6 μm[27] They are in planar configurations and difficult for free-space light to couple in ref. In contact with Au, the Schottky barrier formed at the Au-TiO2 interface is about 1.07 eV5 In this structure, the sunlight can be efficiently coupled by the gradual openings into the nanoslots, where propagating SPPs are generated and almost totally decay into hot carriers. Based on the broadband absorption, better photovoltaic conversion performance is predicted than the previously-reported solid-state plasmonic photovoltaics[22]

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