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FACULTY OF PHYSICS

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2024-11-23 18:27

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Conference: Bucharest University Faculty of Physics 2009 Meeting

Section: Solid State Physics and Materials Science

Title:

Electrical and Photoelectrical Properties of Organic Photovoltaic Cells Based on Polymeric Materials: poly (3-hexylthiophene); 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6, 6) C61

Authors:

Cristina Besleaga(1), Polona Skraba(2), C. Tazlaoanu(1), Sorina Iftimie(1), M. Radu(1), Larisa Magherusan(1), L.Ion(1), G. Bratina(2), S. Antohe(1)

Affiliation:

(1)Faculty of Physics, University of Bucharest, 409 Atomistilor, PO Box MG-11, 077125, Magurele-Ilfov, Romania

(2)University of Nova Gorica ,Vipavska 13, POB 301 SI-5000 Nova Gorica, Slovenia

E-mail

santohe@solid.fizica.unibuc.ro

Keywords:

Polymers, XRD, AFM, Electrical measurements

Abstract:

In recent years there has been a great deal of interest among scientists in the study of polymeric materials, fitted for use in solar energy conversion. Among these, poly (3-hexylthiophene) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6, 6) C61 are probably the best known to date. The photovoltaic response of the ITO/PEDOT/P3HT and ITO/PEDOT/PCBM structures is due to the separation of the photogenerated charge carriers in the built-in electric field, at the rectifying metal/semiconductor interface. The fabrication of these devices can be rather simple and economical as compared with the technology currently used in most inorganic systems. Photovoltaic structures based on poly(3-hexylthiophene) (P3HT), 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) polymers were prepared by spin coating technique, using optical glass substrates covered with 30 nm thick ITO. X ray reflectometry was used for the investigation of the morphology of the surfaces/interfaces of ITO/PEDOT/P3HT/Al and ITO/PEDOT/PCBM/Al structures. Current-voltage (I-V) characteristics of ITO/PEDOT/P3HT/Al samples are non linear and highly asymmetric, with a rectifying factor (RR=If/Ir at the same voltage V), of about 200 at 1.5V, but increasing up to 500 at the 3.5V. In the ITO/PEDOT/PCBM/Al case, I-V characteristics are also asymmetric, with a somewhat lesser rectifying factor, of about 10 at 2 V. Measured action spectra of the cells revealed the same features also observed in absorption spectra of the component polymers. A fill factor of 10% and 14% was measured experimentally, in the case of ITO/PEDOT/P3HT and, respectively, ITO/PEDOT/PCBM structures. Fourth quadrant parameters of the prepared structures, determined in monochromatic light, were observed to shift in time, with respect of their values obtained on as prepared samples. The sample containing P3HT as active layer shows a photovoltaic response due to the exciton dissociation in the internal electric field present at Al/P3HT interface. ITO/PEDOT/PCBM/Al sample shows a very low photovoltaic response, acting almost as a simply photoresistance.