Spectral Dependence Of Photocurrent Research Articles

Effect of the Heterovalent Sc3+ and Nb5+ Doping on Photoelectrochemical Behavior of Anatase TiO2

In this study, we explored the effect of either Nb or Sc doping at a concentration range of 0.0–1.0 at.% on the physical–chemical and photoelectrochemical behavior of TiO2 anatase electrodes. This behavior was characterized by work function, flat band potential, donor density, spectral dependence of photocurrent and stationary photocurrent measurements. All experimental results are interpreted in terms of the formation of the shallow delocalized polaron states in the case of Nb doping and deep acceptor states induced by Sc doping on TiO2 anatase.

Optimized spacer layer thickness for plasmonic-induced enhancement of photocurrent in a-Si:H

Plasmonic interfaces consisting of silver nanoparticles of different sizes (50–100 nm) have been processed by the self-assembled dewetting technique and integrated to hydrogenated amorphous silicon (a-Si:H) using SiNx spacer layers to investigate the dependence of optical trapping enhancement on spacer layer thickness through the enhancements in photocurrent. Samples illuminated from the a-Si:H side exhibit a localized surface plasmon resonance (LSPR) that is red-shifted with the increasing particle size and broadened into the red with the increasing spacer layer thickness. The photocurrent measured in a-Si:H is not only consistent with the red-shift and broadening of the LSPR, but exhibits critical dependence on the spacer layer thickness also. The samples with plasmonic interfaces and a SiNx spacer layer exhibit appreciable enhancement of photocurrent compared with flat a-Si:H reference depending on the size of the Ag nanoparticle. Simulations conducted on one-dimensional square structures exhibit electric fields that are localized near the plasmonic structures but extend appreciably into the higher refractive index a-Si:H. These simulations produce a clear red-shift and broadening of extinction spectra for all spacer layer thicknesses and predict an enhancement in photocurrent in agreement with experimental results. The spectral dependence of photocurrent for six plasmonic interfaces with different Ag nanoparticle sizes and spacer layer thicknesses are correlated with the optical spectra and compared with the simulations to predict an optimal spacer layer thickness.

Photocarrier Excitation and Transport in Hyperdoped Planar Silicon Devices

ABSTRACTWe report an experimental study of photocarrier lifetime, transport, and excitation spectra in silicon-on-insulator doped with sulfur far above thermodynamic saturation. The spectral dependence of photocurrent in coplanar structures is consistent with photocarrier generation throughout the hyperdoped and undoped sub-layers, limited by collection of holes transported along the undoped layer. Holes photoexcited in the hyperdoped layer are able to diffuse to the undoped layer, implying (μτ)h ∼ 5 × 10−9 cm2/V. Although high absorptance of hyperdoped silicon is observed from 1200 to 2000 nm in transmission experiments, the number of collected electrons per absorbed photon is 10−4 of the above-bandgap response of the device, consistent with (μτ)e < 1 × 10−7cm2/V.

Photo-detecting characteristics of double barrier structures

Spectral dependence of photocurrent is calculated for the structure with narrow basis (with thickness equal to ∼1μk) located between two counter barriers, in view of the reflecting characteristics of junctions. In the spectral characteristics, change of the photocurrent sign is obtained. It is also shown that spectral sensitivity and inversion point location depend both on reflecting characteristics of rear junction and on external bias voltage. Physical explanations of indicated photoelectric processes are also given.

Effect of surface recombination on the spectral dependence of photocurrent in intrinsic hydrogenated amorphous silicon films

The spectral dependence of the photocurrent in intrinsic hydrogenated amorphous silicon (a-Si:H) films was measured in the annealed and light-soaked states. The photocurrents were modeled using numerical analysis which quantified the recombination in both the bulk as well as at the film surface and glass substrate interface. The results on films, having thicknesses between 1 and 3 μm, are consistent with thickness independent bulk transport properties and surface and substrate interface recombination velocities of (3–6)×104 and (1–2)×106 cm/s, respectively.

Photoconduction in proteins.

SZENT-GYORGI1 has reported large conductivity increases in illumination of protein films stained with coloured dyes. Riehl2,3 found a photoconductivity in gelatine on 366 nm irradiation and Douzou and Thullier4 reported a photocurrent in serum albumin films on illumination with visible light. Nelson5 has measured the action spectra of haemoglobin and gelatin in vacuo, and observed a similar wavelength dependence for both photoconduction and photoemission with a “λ0” threshold near 3.9 eV. Vladimirov and Timofeyev6 found a similar spectral dependence of photocurrent for thin films of actomyosin and trypsin. Liang7 has observed photocurrents on illumination of polyglycine I and II with a tungsten lamp. No spectral dependencies for protein photocurrents at below 3.9 eV have been reported.