A variety of approaches are examined for exploiting the optical properties of metal or dielectric nanoparticles, particularly those associated with surface plasmon polariton resonances, to improve the performance of semiconductor photodetectors and photovoltaic devices. Early and recent concepts for employing optical absorption and local electromagnetic field amplitude increases associated with surface plasmon polariton excitation to improve photocurrent generation in organic photovoltaic devices are briefly reviewed. The application of optical scattering properties of nanoparticles to improve transmission of optical power into, and consequently photocurrent response in, Si and a-Si:H photodiodes is then described, and effects related to scattered-wave phase shifts and interference effects between scattered and directly transmitted wave components in producing either enhancement or suppression of photocurrent response at different wavelengths are discussed. Coupling of photons incident normal to the surface of a semiconductor thin-film device into lateral, optically confined paths within waveguide structures formed by refractive index contrast either within the semiconductor structure, or between the semiconductor and surrounding dielectric material, is discussed in the context of early and recent studies of such coupling in silicon-on-insulator photodetectors, and recent work on engineering of photon propagation paths in III-V compound semiconductor quantum well solar cells.
We describe experimental and theoretical analysis of coupling of light scattered by metal or dielectric nanoparticles into
waveguide modes of InP/InGaAsP quantum-well solar cells. The integration of metal or dielectric nanoparticles above
the quantum-well solar cell device is shown to couple normally incident light into lateral optical propagation paths, with
optical confinement provided by the refractive index contrast between the quantum-well layers and surrounding material.
Photocurrent response spectra yield clear evidence of scattering of photons into the multiple-quantum-well waveguide
structure, and consequently increased photocurrent generation, at wavelengths between the band gaps of the barrier and
quantum-well layers. With minimal optimization, a short-circuit current density increase of 12.9% and 7.3% and power
conversion efficiency increases of 17% and 1% are observed for silica and Au nanoparticles, respectively. A theoretical
approach for calculating the optical coupling is described, and the resulting analysis suggests that extremely high
coupling efficiency can be attained in appropriately designed structures.