Time-resolved opto-electronic properties of poly(3-hexylthiophene-2,5-diyl): Fullerene heterostructures detected by Kelvin force microscopy

• Published in: Thin solid films Vol. 519; no. 2; pp. 836 - 840
• Main Authors: Čermák, Jan, Rezek, Bohuslav, Cimrová, Věra, Fejfar, Antonín, Purkrt, Adam, Vaněček, Milan, Kočka, Jan
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.11.2010; Elsevier
• Subjects: Applied sciences; Atomic force microscopy; Blends; Bulk-heterojunction; Butyric acid; Charge carriers: generation, recombination, lifetime, trapping, mean free paths; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronic transport phenomena in thin films and low-dimensional structures; Energy; Esters; Exact sciences and technology; Fullerenes; Fullerenes and related materials; diamonds, graphite; Indium tin oxide; Kelvin force microscopy; Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids); Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Microscopy; Natural energy; Photovoltaic conversion; Photovoltaics; Physics; Solar cells. Photoelectrochemical cells; Solar energy; Specific materials; Thin films; Trapping; Atomic force microscopy; Kelvin force microscopy; Bulk-heterojunction; Photovoltaics; Polymer blends; Optoelectronic properties; Photoinduced effect; Time resolved spectra; Photovoltaic cell; Thin films; Charge carrier trapping; Time resolution; Photovoltaic cells; Thiophene derivative polymer; Spin-on coatings; Fullerenes; Heterojunctions; Butyric derivative polymer; Spin-on coating; Sol-gel process; Electron donor; Heterostructures; Surface potential
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2010.08.132

Thin blend polymer films made of poly(3-hexylthiophene-2,5-diyl) (electron donor) and fullerene derivatives as electron acceptors ([6,6]-thienylC61 butyric acid methyl ester and [6,6]-thienylC71 butyric acid methyl ester) are prepared by the spin-coating technique on indium tin oxide covered glass substrates. Time-resolved photo-induced changes of surface potentials are detected by Kelvin force microscopy (KFM). Changes of surface potentials by 10–150 mV reveal different quality and kinetics of charge generation in the two blends in short (minutes) and long (hours) time periods. This is attributed to a combination of electron accumulation, trapping, and organic material degradation under ambient conditions. As KFM characterizes the blend films directly without metal contact layer, it reveals differences in the opto-electronic behavior of the blends, which are not detected by common photovoltaic cell characterization.