Photoresponse Of Thin Films Research Articles

Photoresponse in thin films of WO3 grown by pulsed laser deposition

We report, the photoresponse behaviour of Tungsten trioxide (WO3) films of different surface morphology, grown by using pulsed laser deposition (PLD). The Growth parameters for PLD were changed for two substrates SiO2/Si (SO) and SrTiO3 (STO), such a way which, result nanocrystalline film on SO and needle like structured film on STO. The photoresponse is greatly modified in these two films because of two different surface morphologies. The nanocrystalline film (film on SO) shows distinct photocurrent (PC) ON/OFF states when light was turned on/off, the enhancement of PC is ∼27%. Whereas, the film with needle like structure (film on STO) exhibits significantly enhanced persistent photocurrent even in light off condition, in this case, the enhancement of PC ∼ 50% at room temperature at lowest wavelength (λ = 360 nm) at a nominal bias voltage of 0.1 V.

Birefringence improvement in azopolymer doped with MFI zeolite nanoparticles

AbstractHybrid organic/inorganic materials based on combination of polymers and inorganic nanoparticles (NP) attract considerable attention due to their advantageous electrical, optical, or mechanical properties. Recently it was reported that doping photopolymers with nanoparticles allows to achieve near 100% net diffraction efficiency in case of conventional holographic recording. Thus, we have synthesized novel organic/inorganic composite materials by incorporating MFI (Mordenite Framework Inverted) type zeolite nanoparticles in an amorphous side-chain azopolymer. A considerable improvement of the photoresponse in thin films of these composite materials has been observed compared to the non-doped samples - nearly 25% increase of the saturated value of the birefringence.Moreover the photoinduced birefringence is stable in time which allows these materials to be used as media for diffractive optical elements with high efficiency and unique polarization properties.

Photoelectrochemical studies of thin films of several tetraphenylporphyrins deposited on tin(IV) oxide electrodes

The photoresponses of thin films of various metallotetraphenylporphyrins, MTPP, free-base tetraphenylporphyrin, TPP, and tetra(4-carboxyphenyl)porphyrin, (o-C2H3O2)TPP, have been investigated. The films were deposited on SnO2 electrodes and placed in a wet cell. The photoresponse for the water-splitting cell was very low for all compounds, presumably because of the unfavourable relative positions of the energy levels involved. With hydroquinone in the electrolyte solution the photocurrent quantum efficiencies for films 50 A thick were 8.6 × 10–3, 1.1 × 10–2, 1.0 × 10–2 and 1.6 × 10–2 for MgTPP, ZnTPP, TPP and (o-C2H3O2)TPP, respectively. No photoresponses were observed for CoTPP, CuTPP and NiTPP. This is attributed to the occurrence of fast radiationless processes, which prevent electron injection into the semiconductor. Some data are presented which may indicate that the singlet excited state is the precursor for charge separation. The photoresponse as a function of the film thickness shows clearly that multilayer activity takes place, although it could not be described using a simple exciton-diffusion model. The photoresponse of thin films of (o-C2H3O2)TPP is attributed to a strong interaction between these molecules and the semiconductor surface.