Photoelectric characteristics of lead phthalocyanine/titanium oxide structures

Abstract

A study has been carried out into the conduction, charge transfer/electron injection and photovoltaic conversion properties of TiO 2 -lead phthalocyanine (PbPc) heterojunctions. The results indicate that although the heterojunction area, and hence overall conversion efficiency, was low for the planar device structures used in the investigation, electron injection and effective charge separation across the dye-TiO 2 interface was achieved, with open circuit voltages in the region of 0.3 V. The conversion efficiency was found to be a function of the thickness of the phthalocyanine layer, increasing by a factor of more than 30 times as the thickness of the dye layer was reduced from 500 to 100 nm. The results suggest that under appropriate deposition conditions, to ensure effective coating of the inorganic phase, such phthalocyanine dyes may offer potential for use in dye sensitized photovoltaic cells.

Hybrid Junctions of Zinc(II) and Magnesium(II) Phthalocyanine with Wide-Band-Gap Semiconductor Nano-oxides: Spectroscopic and Photoelectrochemical Characterization

“…The experimental evidence of detectable photocurrents for bare dye electrodes supports the establishing of a potential p−n junction, thus confirming the p-type semiconducting behavior of Zn II Pc and Mg II Pc, ascribed to the extensive π-conjugated system of the 18 mobile π electrons. , In addition, oxygen molecules strongly bound to MPcs have been suggested to act as dye p-dopants, resulting in the formation of a space layer at the ITO/dye interface, and dye p-doping has been demonstrated to occur also with oxygen that originates from the ITO surface …”

“…Moreover, both phthalocyanines and porphyrins represent attractive alternatives to the expensive and polluting pyridyl-based homologous (N3 dyes), offering, in addition, a higher molar extinction coefficient in the near-infrared region. However, phthalocyanine- or porphyrin-based cells still do not reach the power conversion efficiencies obtained when N3 dyes are used in the same systems (10−11%) . Photoelectrochemical devices based on phthalocyanine dyes are, in fact, limited by their intrinsic poor electrical conductivity, because the relaxation process of excited states in Pc solid materials has been referred to exciton migration and following capture, at the radiative and nonradiative traps sites. , …”

“…Owing to the large π systems, free bases and metal phthalocyanines are known to associate in the form of dimers and/or oligomers through hydrogen bonds, van der Waals and electrostatic interactions, and hydrophobic effects . The balance between these forces and external effects (e.g., solvent and temperature or coating process when deposited into films) determines the type of molecular assembly. ,, A large number of investigations have been focused on the aggregation behavior of Pc compounds − because these molecular assemblies have shown electrochemical, spectroscopic, photophysical, and conducting properties different from those of the corresponding monomer . In the aggregates, the transition dipole moments of monomers are strongly coupled, causing changes in the absorption spectra that strongly depend on the angle (φ) between the coupled transition dipole moments and the line joining the molecule centers.…”

Homogeneous and Heterogeneous Free-Based Porphyrins Incorporated to Silica Gel as Fluorescent Materials and Visible Light Catalysts Mimic Monooxygenases

“…Such materials have many potential applications due to their catalytic, biosensing, optical, photo-electronic, photonic, and nanobiophotonic properties (Lan et al, 1999;Gill & Ballesteros, 2000;Ariga et al, 2007;Escribano et al, 2008). Porphyrins have been encapsulated in sol-gel materials (either in monolithic blocks or as thin layers on various supports) because of their ability of photoconduction and photoemission, in the context of their application as fluorescent materials (Papkovsky et al, 2000;García-Sánchez et al, 2006;De la Luz et al, 2007) optical sensors (Delmarre & BiedCharreton, 2000;Im et al, 2005), dye sensitive solar cells (Grätzel, 2001;Ray et al, 2001), and non-linear absorption (Sun et al, 1997), mesoporous materials (Ariga et al, 2007), as well as sensitizers in photodynamic therapy (PDT) (Reisfeld, 2001;Podbielska et al, 2006).…”

Fabrication and Characteristics of ZnO/OAD-InN/PbPc Hybrid Solar Cells Prepared by Oblique-Angle Deposition

“…Among organic materials, lead phthalocyanine (PbPc) is a well-known organic semiconductor, and thin films of PbPc have a wide range of possible applications, including solar cells, gas sensors, and electroluminescence devices, owing to its easy synthesis and strong substantial absorption in the visible and near infrared [ 7 , 8 , 9 , 10 ]. A TiO 2 -PbPc heterojunction-based organic/inorganic hybrid photovoltaic solar cell was reported and the efficiency was poor (only 0.046%) [ 11 ]. However, InN enables III-nitride optical devices to cover the whole visible spectrum and extend into the infrared region, such that InN is a potential material for optoelectronics applications, including solar cells, to substitute for the TiO 2 layer [ 12 , 13 , 14 , 15 , 16 , 17 ].…”