The emerging field of plasmonics has yielded methods for guiding and localizing light at the nanoscale, well below the scale of the wavelength of light in free space. Now plasmonics researchers are turning their attention to photovoltaics, where design approaches based on plasmonics can be used to improve absorption in photovoltaic devices, permitting a considerable reduction in the physical thickness of solar photovoltaic absorber layers, and yielding new options for solar-cell design. In this review, we survey recent advances at the intersection of plasmonics and photovoltaics and offer an outlook on the future of solar cells based on these principles.

Plasmonics for improved photovoltaic devices

The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

The remarkable performance of lead halide perovskites in solar cells can be attributed to the long carrier lifetimes and low non-radiative recombination rates, the same physical properties that are ideal for semiconductor lasers. Here, we show room-temperature and wavelength-tunable lasing from single-crystal lead halide perovskite nanowires with very low lasing thresholds (220 nJ cm(-2)) and high quality factors (Q ∼ 3,600). The lasing threshold corresponds to a charge carrier density as low as 1.5 × 10(16) cm(-3). Kinetic analysis based on time-resolved fluorescence reveals little charge carrier trapping in these single-crystal nanowires and gives estimated lasing quantum yields approaching 100%. Such lasing performance, coupled with the facile solution growth of single-crystal nanowires and the broad stoichiometry-dependent tunability of emission colour, makes lead halide perovskites ideal materials for the development of nanophotonics, in parallel with the rapid development in photovoltaics from the same materials.

Lead halide perovskite nanowire lasers with low lasing thresholds and high quality factors

Optical generation of hot electrons in metallic structures and its potential as an alternative to conventional electron–hole separation in semiconductor devices are reviewed. The possibilities for realizing high conversion efficiencies with low fabrication costs are discussed along with challenges in terms of the materials, architectures and fabrication methods

Plasmon-induced hot-electron generation at nanoparticle/metal-oxide interfaces for photovoltaic and photocatalytic devices

Optical Waveguide Theory

Quantum dot-based integrated optoelectronic devices using two different techniques are reported. Selective area epitaxy is used to fabricate a laser integrated with a waveguide while the post-growth technique of impurity free vacancy disordering is used to fabricate multi-color infrared photodetectors.

Quantum Dot-based Integrated OptoelectronicDevices

We present results on integrated photonic devices fabricated using InGaAs quantum-dots. Selective-area MOCVD is used to tune the bandgap of epitaxial layers for device integration.

Photonic device integration using MOCVD grown quantum dots

A single GaAs nanowire (NW) photodetector (PD) is fabricated based on the back-to-back Schottky diode structure. Optoelectronic properties are characterized by measuring device photocurrent, and also the spectral response, which indicates our device is very sensitive and applicable as a PD.

Optoelectronic properties of GaAs nanowire photodetector

The results of nucleation of InGaAs and InAs quantum dots by selective area epitaxy are presented. By pre- patterning the substrates with different (SiO2) mask dimensions, the bandgap of the quantum dots can be tuned over a large range. This technique is used to demonstrate a quantum dot laser integrated with a quantum well waveguide.

Integration of Quantum Dot devices by Selective

Semiconductor nanowires grown via the vapour-liquid-solid (VLS) mechanism are promising for miniaturisation of optoelectronic devices. Efficient optoelectronic devices require these nanowires to have high quantum efficiency. While optimizing the growth process to eliminate bulk defects and achieve perfect surface passivation is one approach to increase the quantum efficiency of nanowires1, coupling the nanowires to resonant plasmonic structures to reduce the radiative lifetime of carriers in the semiconductor is an alternative approach. In this paper, we demonstrate increase in quantum efficiency of AlGaAs shell of GaAs core-AlGaAs shell-GaAs cap nanowires (Figure 1(a)) by coupling the nanowires to plasmonic nanoparticles deposited on their surface. Increase in quantum efficiency of the AlGaAs shell leads to multi-colour emission from the nanowires (from the band-edge of GaAs core and the AlGaAs shell). This approach to achieve multi-colour emission from the nanowires does not rely on the growth of quantum confined layers like quantum wells or quantum dots in the nanowires. In addition to achieving multi-colour emission, our approach also provides independent control on the polarization response of emission from the GaAs core and the AlGaAs shell of the nanowires2.

Sudha Mokkapati

Papers

Quantum Dot-based Integrated OptoelectronicDevices

Photonic device integration using MOCVD grown quantum dots

Optoelectronic properties of GaAs nanowire photodetector

Integration of Quantum Dot devices by Selective

Multi-colour emission from GaAs core-AlGaAs shell photonic nanowires