Dejun Wang

Photoluminescent and photovoltaic properties observed in a zinc borate Zn2(OH)BO3

A chiral zinc borate Zn2(OH)BO3, which exhibits nonlinear optical, photoluminescent and photoelectronic properties, has been successfully prepared through a hydrothermal reaction. The structure of the compound has a ZnO matrix and the electronic structure of the compound can be regarded as that for ZnO modified by the presence of B atoms. The luminescence properties of Zn2(OH)BO3 were characterized by excitation and emission spectra. Photovoltage signals were observed for the as-synthesized compound and for samples calcined at various temperatures by surface photovoltage spectroscopy (SPS) and field-induced surface photovoltage spectroscopy (FISPS). The results show that Zn2(OH)BO3 has photoelectric transformation ability. Either thermal treatment or application of an external electric field enhances the photovoltage responses of the compound to a considerable extent.

Photovoltaic properties of polythiophene nano-tubule films

Abstract The electronic properties of the polythiophene nano-tubule films were studied with surface photovoltage spectrum (SPS) and field-induced surface photovoltage spectrum (FISPS). The surface photovoltaic responses were resulted from the π–π ∗ transition of polythiophene chains. Two extra photovoltaic responses in the near-IR region were observed under the external electric field. Based on the band theory and the principle of FISPS, these responses were ascribed to the charged surface electronic states, which were led by the interaction between polythiophene nano-tubules and the oxygen absorbed on the surface.

Electrochemical deposition and photovoltaic properties of Nano-Fe2O3-incorporated polypyrrole films

Abstract Fe 2 O 3 nanoparticles, of which sizes vary from 4 to 40nm, were introduced into polypyrrole(PPy) films while pyrrole monomers were electrodeposited onto ITO electrodes. When measured in surface photovoltage spectroscopy(SPS), new photovoltaic behaviors were observed in both, cases containing small and large Fe 2 O 3 particles. In terms of band structure and polaron theory, together with the reference of absorption spectra, some principles involved were revealed.

Photovoltaic properties of novel conjugated oligomer/n-Si(111) heterostructrues

Abstract The photovoltaic properties of three kinds of novel organic conjugated oligomers synthesized using horseradish peroxide (HRP) as a catalyst, poly(8-hydroxyquinoline-hydroquinone) (A), poly(8-hydroxyquinoline-1,5-dihydroxynathphelene) (B) and poly(8-hydroxyquinoline-4-phenylphenol) (C) were studied by surface photovoltage spectroscopy (SPS). The interface charge processes of conjugated oligomers/n-Si(111) were investigated by SPS and the current–voltage (I–V) technique, respectively. The photovoltaic response intensities of the oligomers/n-Si were increased by varying degrees over that of the bare n-Si. A new surface photovoltaic response band appears in the SPS curve of A/n-Si or C/n-Si in the region of 360–450 nm. The I–V curves of the oligomers/n-Si heterostructure showed that they have good rectification character.

Lanthanide complexes with acetylacetonate and 5,10,15,20-tetra[para-(4-flourobenzoyloxy)-meta-ethyloxy]phenylporphyrin

Abstract Lanthanide complexes of acetylacetonate and 5,10,15,20-tetra[para-(4-flourobenzoyloxy)-meta-ethyloxy]phenylporphyrin having the general formula Ln[(FBOEP) 4 P]acac (where Ln=Ho, Er, Yb, Lu; FBOEP=[para-(4-flourobenzoyloxy)-meta-ethyloxy]phenyl; Hacac=acetylacetone; P=porphyrin) have been prepared and characterized. A structure is proposed in which one 5,10,15,20-tetra[para-(4-flourobenzoyloxy)-meta-ethyloxy]phenylporphyrin is coordinated to a rare earth ion in a tetradentate fashion, while one acetylacetonate is coordinated to the same metal ion in a bidentate fashion. We investigated the photo-generated charge behavior of the ligand and the complex, Lu[(FBOEP) 4 P]acac, by means of surface photo-voltage spectroscopy (SPS) and field induced surface photo-voltage spectroscopy (FISPS) which are useful tools to investigate the photo-physics of excited states generated by absorption in the aggregate state.

Optical and electrical properties of organic-inorganic composite system

Abstract Anionic phthalocyanine sodium hydrogallium 4,4′,4″,4‴-tetrasulfonated phthalocyanine(GaTsPc) was used to modify the surface of a size-quantized particulate TiO 2 photoelectrode fabricated by electrostatic attraction. The photovoltaic features and interfacial electron transfer of the electrodes were studied by a photoelectrochemical method and surface photovoltage spectroscopy. The results indicate that the light absorption of phthalocyanine monomer makes more contribution to the photovoltaic response in the TiO 2 /GaTsPc composite electrode in spite of obvious aggregation occurring in composite electrode.

A study of the photovoltage properties of nanocrystalline LiFe5O8

Abstract We have researched nanocrystalline LiFe 5 O 8 during reflection absorption, surface photovoltage and surface photovoltage (SPS) by changing electric field (FMSPS). It is shown that the samples have bands of charge transfer transitions and crystal field transition. It is shown obvious quantum size effect that the absorbent intensity increased with decreasing particle size. The nanocrystal has P-type photovoltage property. The two peaks are served in 610 and 680 nm in particle size of less than 30 nm. For the first time, we researched the charge transfer transition bands in FMSPS. It is shown that the bands consisted of two transitions of different properties. The photovoltage process is also explained.

Effect of different substituents on conducting character of azos and local states of azo/TiOPc composites

The conducting character of the azo pigments of 4,4′-2-{N-[β-hydroxyl-γ-(p-methoxylanilino) naphthyl]}azodiphenyl (DCRL) and 4,4′-2-{N-[β-hydroxyl-γ-(m-nitroanilino)naphthyl]} azodiphenyl (DCBS) is examined by surface photovoltaic spectrum (SPS) and field induced surface photovoltaic spectrum (FISPS). The different responding behaviors to external fields indicate that DCRL and DCBS are an n-type and a p-type semiconductor, respectively. Electron withdrawing (donating) groups ue5f8NO2 (ue5f8OCH3) pull (push) the electrons from (to) central azo backbone and lower (boost up) the Fermi level thereby determine its conduction character. When they are incorporated into a p-type semiconducting film of titanyl-oxo-phthalocyanine (TiOPc), both TiOPc/DCRL and TiOPc/DCBS composites show surface photovoltaic signals significantly reduced in the magnitude in comparison with that of pure TiOPc, suggesting that the built-in field between TiOPc/electrode junction is sensitive to azo compounds. With respect to TiOPc/DCRL composite (20% DCRL by wt.), in near-IR spectral region, the FISPS demonstrates symmetric responses to both positive and negative fields, which are associated with local states. However no characteristic local state responses are observed in TiOPc/DCBS composite (20% DCBS by wt.). The formation of donor/acceptor system between p-type TiOPc and n-type DCRL is a reasonable ascription to the observed phenomenon.

Improved surface photovoltaic response of nanoparticulate TiO2-pyridine derivative monolayer/n-Si(111) assembly

Abstract Nanoparticulate TiO 2 -pyridine derivative monolayer/n-Si(111) assembly was fabricated by Langmuir-Blodgett (LB) technique from 4-[4′-N,N-(didodecylamino) stryll pyridium (P II ), and its photovoltaic conversion properties were investigated by surface photovoltage spectroscopy. Sensitization effect of P II molecule as well as TiO 2 nanoparticle on n-Si(111) is observed, and the photovoltaic response of this assembly is about 20 times as high as that of n-Si(111).

Optoelectronic behavior of conjugated polymer/silicon heterojunctions

Abstract PPy and PAn thin films were deposited onto silicon wafers (n-type) through electrochemical method. Their optoelectronic behavior was studied by surface photovoltage spectroscopy (SPS) and electric-field modulation technique. Results were interpreted reasonably by the effect of polaron-involved photo-sensitization.