[Show abstract][Hide abstract] ABSTRACT: In this study double linked porphyrin-fullerene and phthalocyanine-fullerene dyads and a single linked phthalocyanine-fullerene dyad were studied as components in inverted organic solar cells (OSCs) equipped with the well known P3HT:PCBM bulk heterojunction as the photoactive layer. The dyad monolayers were deposited onto a surface of P3HT:PCBM by using the Langmuir-Schäfer method, therefore forming oriented monolayers in which the electron donor (D) and the acceptor (A) exist as a close proximity pair in a 1:1 molar ratio. As a result of this structure short circuit current density (J(sc)), open circuit voltage (V(oc)), and power conversion efficiency (η) increased, while the fill factor (FF) remained the same. The devices which contained dyads with double linkage produced higher efficiencies than the one with a single linked dyad. This result can be explained in terms of molecular orientation. It was also verified that the prepared OSC devices have promising long term air stability.
Physical Chemistry Chemical Physics 03/2012; 14(10):3498-504. · 3.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Three new tetracyclic 8-hydroxyquinoline derivatives were synthesized by using a Pd catalyzed intramolecular direct arylation reaction in a key step. Furthermore, the new compounds were used as ligands in aluminium complexes and their photophysical properties were studied in detail both in solution and solid state by using absorption, steady-state, and time resolved fluorescence spectroscopies. Results show especially that the aluminium complex of 11H-indolo[3,2-c]quinolin-4-ol has the most blue-shifted emission maximum among the Alq3 derivatives to date and CIE chromaticity coordinates locate on the deep blue area (0.16, 0.12). Moreover, the fluorescence quantum yield of this compound is 3.1–3.5 times higher compared with the parent Alq3. Photophysical properties of the complex did not show major differences between the solution and the solid states. The lack of melting endotherm in DSC analysis indicates that the compound is amorphous. Based on the results, 11H-indolo[3,2-c]quinolin-4-ol has promising features to be applied as a ligand for aluminium or other metal ions in different applications.
Journal of Materials Chemistry 09/2011; 21(38):14766-14775. · 5.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Liquid phthalocyanine and fullerene derivative monomers were synthesized, which can be cationically polymerized either thermally or by light and are suitable for preparing complex solar cell structures, obtainable only by organic vacuum deposition till now. A sandwich solar cell with a bulk heterojunction layer between single layers was shown to produce higher currents and voltages than either pure bilayer or pure bulk heterojunction. The proposed in situ polymerization method can be applied to a variety of active layers for preparation of solution-processed solar cells. (C) 2010 Elsevier B.V. All rights reserved.
Solar Energy Materials and Solar Cells 03/2011; 95(3):909-916. · 5.03 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The organization of π-π stacking perylenediimide (PDI) derivative, PDI12, was studied in solution and in thin films. Films were prepared with the Langmuir-Schaeffer (LS) method and characterized by means of AFM, optical profilometry, steady-state absorption, emission, fluorescence lifetime, and transient photovoltage measurements. The columnar aggregates observed previously in PDI12 solutions and in spin-coated films persist also in LS films. Because of the specific conditions during the preparation of the LS film, i.e., hydrophobic interactions and lateral compression, the columnar aggregates seem to organize with their long axis perpendicular to the layer plane whereas in spin-coated films the columns were oriented parallel to the layer plane. According to AFM and profilometer results, the thickness of LS monolayer of PDI12 is 10 nm, indicating that it consists mainly of aggregates, each containing approximately 30 monomers. Intermolecular photoinduced energy and electron transfer processes in C(60)|PDI12 double layer junction were studied. The fluorescence lifetime of PDI12 film is exceptionally long, but the quenching is very efficient in the presence of C(60). In charge transfer studies, long-lived photovoltage signal was observed for the double layer. Results of this work indicate that PDI12 acts as an electron acceptor and fullerene C(60) as an electron donor.
[Show abstract][Hide abstract] ABSTRACT: Photoinduced intra- and intermolecular electron transfer (ET) in thin films of porphyrin-fullerene dyad (P-F) and perylenetetracarboxidiimide (PTCDI) was studied by means of photoelectrical and spectroscopic methods. Films consisting of smooth 100 mol% layers of P-F and PTCDI were prepared by the Langmuir-Schäfer (LS) technique and thermal evaporation, respectively. The time-resolved Maxwell displacement charge (TRMDC) and laser flash-photolysis methods were utilized to demonstrate photoinduced ET from P-F to PTCDI regardless of which chromophore is photoexcited. Finally, the information about the electron movement in the respective thin films was used to build a layered organic solar cell, whose internal quantum yield (Φ(I)) of collected charges was 13%.
Physical Chemistry Chemical Physics 10/2010; 12(39):12525-32. · 3.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Multistage electron transfer in a film system consisting of a hole-transporting layer (HTL), donor-acceptor pair (D-A), and an electron-transporting layer (ETL) was studied by photovoltage and flash-photolysis techniques. Poly(3-hexylthiophene) (PHT) was used as the HTL, while a symmetric porphyrin-fullerene dyad (P-F) and perylenetetracarboxidiimide (PTCDI) layers were functioning as the D-A pair and ETL, respectively. The photoexcitation of this three-component film system causes charge separations in the monomolecular P-F film, followed by electron transfer from the PHT polymer film and the fullerene anions to the porphyrin cations and the PTCDI layer, respectively. The final transient state is a charged PHT(+)|P-F|PTCDI(-) system, with significantly increased amplitude and lifetime of the photoelectrical signals compared to previously studied P-F|PTCDI and PHT|P-F systems, due to the its increased charge-separation distance. The study promotes the knowledge on the charge transfer mechanism in multilayered film systems.
Photochemical and Photobiological Sciences 09/2010; 9(9):1212-7. · 2.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The capability of Violanthrone-79 (V-79) and N,N′-bis(2,5-di-tert-butylphenyl)-3,4:9,l0-perylenebis(dicarboximide) (PDI) to act as electron acceptors, with respect to poly(3-hexylthiophene) (PHT) and to the photoinduced fullerene anion of porphyrin-fullerene (P-F) dyad, was demonstrated in Langmuir-Blodgett (LB) films by the time-resolved Maxwell displacement charge method. The introduction of V-79 and PDI in oriented multilayered films led to improved light harvesting and increased lifetime of the charge separation, enhancing the photocurrent generation measured using a three-electrode photoelectrochemical cell. The best solar cell performance was achieved for the multifunctional film structure where efficient PHT-phthalocyanine heterojunction (PHT|ZnPH4) was combined with the P-F|V-79 system.
The Journal of Physical Chemistry C 03/2010; 114(18):8559-8567. · 4.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Thin organic films were deposited on silicon oxide surfaces with golden interdigitated electrodes (interelectrode gap was 2 mm), and the film resistivities were measured in dark and under white light illumination. The compounds selected for the measurements include molecules widely used in solar cell applications, such as polythiophene (PHT), fullerene (C60), pyrelene tetracarboxylic diimide (PTCDI) and copper phthalocyanine (CuPc), as well as molecules potentially interesting for photovoltaic applications, e.g. porphyrin–fullerene dyads. The films were deposited using thermal evaporation (e.g. for C60 and CuPc films), spin coating for PHT, and Langmuir–Schaeffer for the layer-by-layer deposition of porphyrin–fullerene dyads. The most conducting materials in the series are films of PHT and CuPc with resistivities 1.2 Â 103 V m and 3 Â 104 V m, respectively. Under light illumination resistivity of all films decreases, with the strongest light effect observed for PTCDI, for which resistivity decreases by 100 times, from 3.2 Â 108 V m in dark to 3.1 Â 106 V m under the light.
[Show abstract][Hide abstract] ABSTRACT: Efficient photoinduced interlayer electron transfer from a phthalocyanine derivative, ZnPH4, to porphyrin cation of a porphyrin–fullerene donor–acceptor dyad was demonstrated by using time-resolved photovoltage technique. Multicomponent thin films with desired layer arrangements were constructed by the Langmuir–Blodgett and spin-coating methods in order to study charge transfer in solid state. As a contradiction to the photovoltage experiments, the dyad monolayer in the film structure did not enhance the current amplitude in electrochemical photocurrent measurements. This is associated with a weak electronic interaction between fullerene and aqueous electrolyte, reducing the photocurrent generation. The use of poly(3-hexylthiophene) as a hole conducting layer was shown to improve photocurrent yield of the device by forming efficient heterojunction together with the ZnPH4 layer.
Thin Solid Films 01/2009; 517(9):2988-2993. · 1.87 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Layers of poly(3-hexylthiophene), PHT, phenyl vinyl thiophene, PVT3, poly(p-phenylene-2,3′-bis(3,2′-diphenyl)-quinoxaline-7-7′-diyl), PPQ, and covalently linked porphyrin−fullerene donor−acceptor dyad, P−F, were deposited as various multilayer films, which then were used to study photoinduced electron transfer and photocurrent generation. The aim of the research was to clarify functioning of different energy and electron donating and accepting layers in charge transfer processes, which were initially created in a film consisting of parallel P−F molecules. The reactions were studied by means of time-correlated and steady-state fluorescence, time-resolved photovoltage, and electrochemical photocurrent measurements. The longest-lived charge-separated state and the highest efficiency of photocurrent generation were obtained for the multilayer structure of PHT|PVT3|porphyrin−fullerene. Porphyrin−fullerene dyads deposited parallel as the Langmuir –Blodgett film transfer electrons from porphyrin to fullerene yielding radical cation and anion moieties, respectively. The dyad on a PHT layer induces electron donation from PHT to the porphyrin cation. When PVT3 is deposited between the PHT and the P−F layers, it promotes both energy and electron transfer to the porphyrin moiety of the dyad, retards the recombination of the primary charge-separated state, and thus increases the photocurrent generation. PPQ was used as an electron acceptor from the fullerene radical anion, causing an increased lifetime of the charge separation.
The Journal of Physical Chemistry C 06/2008; 112(27):10256-10265. · 4.84 Impact Factor