Schematic view of photocurrent dynamics in composite layers.
In collaboration with the University of Strasbourg and ISOF-CNR Bologna, Italy, our group published results of a study of graphene/organic semiconductor composites. Organic thin-film transistor transfer characteristics and time-of-flight (TOF) photoconductivity measurements were used to investigate the effect of the addition of liquid-phase exfoliated graphene nanoflakes (GNs) on the electron mobility in thin films of N,N’-1H,1H-perfluorobutyl dicyanoperylene-carboxydi-imide (PDIF-CN2). Transfer characteristics measurements reveal that the charge carrier mobility of PDIF-CN2 increases by almost three orders of magnitude via blending with GNs. TOF photocurrent measurements confirm that the GNs improve the charge carrier transport in PDIF-CN2. We have found a strong dependence of the TOF-determined electron mobility on the excitation wavelength and obtained a maximum mobility of 0.17 cm2/Vs for charge carriers produced in GN: PDIF-CN2 blends, using photon energy of 5.9 eV. This value is in good agreement with the field-effect mobility of 0.2 cm2/Vs determined from data recorded in the low-voltage region of transfer characteristics. More information can be found in the article.