Temperature Dependence of the Drift Mobility of Poly(9,9 '-dioctylfluorene-co-benzothiadiazole)-Based Thin-Film Devices

Author(s)

Faria, G. C. ; Faria, R. M. ; deAzevedo, E. R. ; von Seggern, H.

• Document type: Journal article
• Source: Journal of Physical Chemistry C; v. 115, n. 51, p. 5-pg., 2011-12-29.

Abstract

Charge transport in spin coated thin films of poly(9,9'-dioctylfluorene-co-benzothiadiazole) (F8BT) was studied using the Photo-Current Extraction by the Linear Increasing Voltage (Photo-CELIV) method in the temperature range of 120 to 420 K. A continuous change in the slope of a In mu versus T-2 plot was detected at 205 K with a very weak temperature dependence of the mobility at lower temperatures. According to the Gaussian Disorder Model (GDM), this behavior can be attributed to a progressive decrease in the dispersiveness of the charge transport. In this sense, the weak temperature dependence of the mobility at low temperatures arises from the nonequilibrium condition between thermal released and trapped charges, so the transport becomes trap controlled at low temperature. Furthermore, another change in the mobility behavior was observed at about 360 K, which was related to the glass transitions of the material. This indicates that even for thin films the drift mobility can be significantly affected by a variation in the dynamics and local packing of the polymer chains, which can be detected by Photo-CELIV (AU)

• FAPESP's process: 09/18354-8 - Dynamics and structure of polymer systems as studied by nuclear magnetic resonance
• Grantee: Eduardo Ribeiro de Azevedo
• Support Opportunities: Regular Research Grants
• FAPESP's process: 07/08688-0 - Electronic and optoelectronic polymer devices
• Grantee: Roberto Mendonça Faria
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 08/01935-5 - Correlation between electric and optical properties with molecular dynamics and physical structure of films and organic devices of polyfluorenes and its derivatives
• Grantee: Gregório Couto Faria
• Support Opportunities: Scholarships in Brazil - Doctorate