Koen Vandewal
University of Hasselt
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Publication
Featured researches published by Koen Vandewal.
Applied Physics Letters | 2009
Koen Vandewal; Wibren D. Oosterbaan; Sabine Bertho; Veerle Vrindts; Abay Gadisa; Laurence Lutsen; Dirk Vanderzande; Jean Manca
The effect of poly(3-alkylthiophene) (P3AT) crystallinity in (nanofiber P3AT):PCBM photovoltaic devices on the energy of the charge-transfer state (ECT) and on the open-circuit voltage (Voc) is investigated for poly(3-butythiophene), poly(3-pentylthiophene) and poly(3-hexylhiophene). P3AT crystallinity, expressed as the crystalline nanofiber mass fraction f to the total P3AT mass in the spin-coating dispersion, is varied between ∼0.1 and ∼0.9 by temperature control. ECT, as obtained by Fourier-transform photocurrent spectroscopy decreased with f as ECT=ECT0−0.2fu2002eV. Alkyl side-chain length only influences ECT0. Voc relates to ECT as Voc=ECT/q−0.6u2002V.
Applied Physics Letters | 2010
Bst Bert Conings; Sabine Bertho; Koen Vandewal; Alessia Senes; Jan D'Haen; Jean Manca; Raj René Janssen
We acknowledge the institute for the promotion of science and technology in Flanders (IWT Vlaanderen) for funding via the IWT-SBO project Polyspec, the Fund for Scientific Research, Flanders (Belgium) (F.W.O.) in the framework of project G.0252.04 and the Special Research Fund (B.O.F.).
Applied Physics Letters | 2006
Olivier Douhéret; Laurence Lutsen; Ann Swinnen; Martin Breselge; Koen Vandewal; Ludwig Goris; Jean Manca
Conductive atomic force microscopy (CAFM) is introduced to perform electrical characterization of organic photovoltaic blends with high spatial resolution. Reference blends used in organic bulk heterojunction solar cells are investigated. The ability of CAFM to electrically evidence phase separated donor and acceptor regions is demonstrated. Furthermore, local spectroscopy is performed to analyze charge transport mechanisms in the blends. Significant modifications of the electrical properties of the semiconducting polymers are shown to occur after blending with fullerene derivatives. Finally, the sensitivity of CAFM to photoelectrical phenomena is revealed. Current variations of few picoamperes are locally observed under illumination of P3HT:PCBM.
Applied Physics Letters | 2008
I. Haeldermans; Koen Vandewal; Wibren D. Oosterbaan; Abay Gadisa; J. D’Haen; M. K. Van Bael; Jean Manca; J. Mullens
The existence of a ground-state charge-transfer (CT) complex in a conjugated polymer:metal oxide nanoparticle bulk heterojunction photovoltaic cell is demonstrated by Fourier-transform photocurrent spectroscopy (FTPS). The CT complex between poly(3-hexylthiophene) (P3HT) and titanium dioxide (TiO2) is characterized by a weak additional photocurrent band (onset 1eV) in the FTPS spectra, situated below the conjugated polymer bandgap of 2eV. The presence of CT interaction between P3HT and TiO2 in relation to frontier orbital alignment is discussed, as well as the contribution of a sub-bandgap interfacial CT state to the electron transfer process in P3HT:TiO2 solar cells.
Advanced Materials | 2010
Abay Gadisa; Kristofer Tvingstedt; Koen Vandewal; Fengling Zhang; Jean Manca; Olle Inganäs
Efficient polymer solar cells typically contain the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), which promotes dissociation of excited states and enhances charge transpo ...
Advanced Functional Materials | 2008
Koen Vandewal; Abay Gadisa; Wibren D. Oosterbaan; Sabine Bertho; Fateme Banishoeib; Ineke Van Severen; Laurence Lutsen; Thomas J. Cleij; Dirk Vanderzande; Jean Manca
Physical Review B | 2010
Koen Vandewal; Kristofer Tvingstedt; Abay Gadisa; Olle Inganäs; Jean Manca
Advanced Functional Materials | 2009
Abay Gadisa; Wibren D. Oosterbaan; Koen Vandewal; Jean-Christophe Bolsée; Sabine Bertho; Jan D'Haen; Laurence Lutsen; Dirk Vanderzande; Jean Manca
Thin Solid Films | 2008
Koen Vandewal; Ludwig Goris; I. Haeldermans; Milos Nesladek; Ken Haenen; Patrick Wagner; Jean Manca
Solar Energy Materials and Solar Cells | 2012
Sylvain Chambon; Raoul Mens; Koen Vandewal; Ewan Clodic; Markus Scharber; Laurence Lutsen; Jan Gelan; Jean Manca; Dirk Vanderzande; Peter Adriaensens