Non-dispersive hole transport in a novel trifluoromethylbiphenylyl substituted PPV derivative

• Published in: Journal of physics. Conference series 2006-01, Vol.28 (1), p.53-56
• Main Authors: Vijila, C, Balakrisnan, B, Huang, C, Chen, Z K, Zhen, C G, Auch, M D J, Chua, S J
• Format: Article
• Language: English
• Subjects: Absorption spectra; Chloroform; Conjugation; Dispersion; Electric fields; Electrical properties; Electroluminescence; Hole mobility; Optical properties; Photoconductivity; Photoluminescence; Physics; Polymers; Room temperature; Solid state; Twisting movement
• ISSN: 1742-6596; 1742-6588; 1742-6596
• DOI: 10.1088/1742-6596/28/1/010

We have studied the optical and electrical properties of a novel electroluminescent polymer, poly[2−(2'-p−trifluoromethyl-phenyl-4',5'-bis(3 -methylbutoxy))phenyl-1,4- phenylene vinylene], using absorption, photoluminescence (PL), photoluminescent quantum yield (ηPL) and time of flight (TOF) photoconductivity techniques. The absorption spectrum in chloroform shows a broad absorption band peaked at 2.92 eV and the PL spectrum shows a maximum at 2.52 eV with vibronic shoulders at 2.38 eV and 2.24 eV. The film state absorption and PL spectra shifted towards the low energy region and the vibronic features are more pronounced compared to that in dilute solution. This is due to the increase of effective conjugation length in the solid state compared to that in solution. The PL quantum yield of the polymer was found to be 44 % in chloroform and 52 % in solid state. The increase of ηPL in solid state compared to liquid state is due to the constraint on the twisting or bending motion of the polymer chains in solid state. The room temperature TOF transients for positive charges showed non-dispersive nature of transport with a mobility of 3.83 × 10−6 cm2/Vs at an electric field of 2 × 105 V/cm. The variation of hole mobility with applied electric field has been studied and analyzed according to disorder formalism.