On the Plasmonic Photovoltaic

Abstract

The conversion of sunlight into electricity by photovoltaics is currently a mature science and the foundation of a lucrative industry. In conventional excitonic solar cells, electron-hole pairs are generated by light absorption in a semiconductor and separated by the "built in" potential resulting from charge transfer accompanying Fermi-level equalization either at a p-n or a Schottky junction, followed by carrier collection at appropriate electrodes. Here we report a stable, wholly plasmonic photovoltaic device in which photon absorption and carrier generation take place exclusively in the plasmonic metal. The field established at a metal-semiconductor Schottky junction separates charges. The negative carriers are high-energy (hot) electrons produced immediately following the plasmon's dephasing. Some of the carriers are energetic enough to clear the Schottky barrier or quantum mechanically tunnel through it, thereby producing the output photocurrent. Short circuit photocurrent densities in the range 70-120 μA cm(-2) were obtained for simulated one-sun AM1.5 illumination with devices based on arrays of parallel gold nanorods, conformally coated with 10 nm TiO2 films and fashioned with a Ti metal collector. For the device with short circuit currents of 120 μA cm(-2), the internal quantum efficiency is ∼2.75%, and its wavelength response tracks the absorption spectrum of the transverse plasmon of the gold nanorods indicating that the absorbed photon-to-electron conversion process resulted exclusively in the Au, with the TiO2 playing a negligible role in charge carrier production. Devices fabricated with 50 nm TiO2 layers had open-circuit voltages as high as 210 mV, short circuit current densities of 26 μA cm(-2), and a fill factor of 0.3. For these devices, the TiO2 contributed a very small but measurable fraction of the charge carriers.

Molecular interfaces for plasmonic hot electron photovoltaics

“…Compared to their best inorganic passivation scheme counterparts (ref. 9), or to other plasmonic hot-electron architectures, 19,51 this represents a significant improvement for plasmonic hotelectron plasmonic based photovoltaics both in terms of J sc , V oc and IPCE. The use of molecular layers to modify interfacial properties opens also exciting avenues in hot-electron photodetectors, where the height of the Schottky barrier, ultimately limiting up to what extent IR light could be harvested, 26 can now be tailored.…”

“…In those approaches, metal nanostructures act as passive elements that introduce parasitic ohmic losses. However, it was shown recently that, a direct photoelectric energy conversion from light absorbed in the metal is within reach, by properly harnessing the hot-electron population derived from the Landau damping of these plasmonic resonances, [9][10][11][12][13][14][15][16][17][18][19][20] This opens the exciting possibility of a new sensing and light harvesting technology, whose spectral response can be tailored by properly modifying the topology of a metal nanostructure, and is beyond the band-to-band absorption paradigm in traditional semiconductors. 11 Theoretical predictions set maximum photovoltaic power conversion efficiencies that range from 10% to 22% depending on the applied model for hot electron population and emission.…”

Modified optical absorption of molecules on metallic nanoparticles at sub-monolayer coverage

“…With a large detuning from the plasmon resonance, distinct shifts and broadening of the molecular resonances reveal the intrinsic properties of the dye in contact with the metal colloid, in contrast to the often studied strong-coupling regime where the optical properties of the dye-molecules cannot be isolated. The observation of these shifts together with the ability to routinely measure them has broad implications in the interpretation of experiments involving resonant molecules on metallic surfaces, such as surface-enhanced spectroscopies and many aspects of molecular plasmonics.Over the last two decades, the optical properties of metallic nanoparticles (NPs) of various sizes and shapes [1] [18][19][20]. Many of these existing and emerging applications are underpinned by the fact that the optical (electronic) absorption of molecules on the surface of metallic NPs is enhanced.…”

“…Over the last two decades, the optical properties of metallic nanoparticles (NPs) of various sizes and shapes [1] [18][19][20]. Many of these existing and emerging applications are underpinned by the fact that the optical (electronic) absorption of molecules on the surface of metallic NPs is enhanced.…”

“…More recent applications are emerging, leveraging this understanding of plasmonic optical properties and relying on the rigorous modelling offered by electromagnetic theory: we can cite for example the development of new types of chiroptical spectroscopies [12], the enhancement of photochemical reactions on surfaces [13][14][15][16], enhanced light emission in LEDs [17], or improved photovoltaics [18][19][20]. Many of these existing and emerging applications are underpinned by the fact that the optical (electronic) absorption of molecules on the surface of metallic NPs is enhanced.…”