Separate charge transport pathways determined by the time of flight method in bimodal polytriarylamine

Abstract

Time of flight photocurrent transient studies on thin films of bimodal polytriarylamine (PTAA) show two distinct and separate arrival times for hole transport in the same sample at a single field. The corresponding mobilities differ by two orders of magnitude, typically μfast∼10−3 cm2 V−1 s−1 and μslow∼10−5 cm2 V−1 s−1 at room temperature, and are measured parametric in electric field and temperature. The mobility data are analyzed using the correlated disorder model by Novikov, yielding a fitting parameter set. The two conduction paths are believed to come about as a result of phase segregation between the shorter and longer polymer chains with the shorter chains giving rise to the faster conduction pathways (as confirmed by results obtained for monomodal, shorter, and longer chain PTAA, by sample thickness scaling of the photocurrents and by reversal of the illuminated electrode). Separate arrival times are also obtained in a blend of the two short and long chain monomodal polymers. The phase separation within the film is inferred by the appearance of two glass transition temperatures using dynamic mechanical thermal analysis.

High charge-carrier mobilities in blends of poly(triarylamine) and TIPS-pentacene leading to better performing X-ray sensors

“…the area under the transient curves) with an increase in the applied voltage. This observation is attributed to the field dependence of the carrier drift length, as has been found elsewhere [7,22]. The transient photocurrents in our devices exhibit some dispersive behaviour, which is commonly observed in polymer-based systems [7,8,[22][23][24].…”

“…This observation is attributed to the field dependence of the carrier drift length, as has been found elsewhere [7,22]. The transient photocurrents in our devices exhibit some dispersive behaviour, which is commonly observed in polymer-based systems [7,8,[22][23][24]. An effective lifetime (τ) was found on a double logarithmic plot as the intersection of asymptotes to the plateau and the linear region of transient's trailing edge [25,26], as is shown in the inset of Figure 2A.…”

“…Therefore, field-effect mobility of TIPS-pentacene cannot be used as a Charge transport in conjugated polymer systems occurs through the hopping of charge carriers from one site to another. Barard et al [22] have employed the correlated disorder model [32,33] to analyse the time-of-flight mobility data of a PTAA-based device. The effect of the positional disorder was found to be greater than the energetic disorder at room temperature and the mobility showed a weak negative field dependence.…”

Characterization of thick film poly(triarylamine) semiconductor diodes for direct x-ray detection

“…PTAA polymers have been shown to have high charge carrier mobilities ͑especially when the molecular weight is low͒ 10 and are operationally and environmentally very stable due to a high ionization potential. 11 Indeed, organic field effect transistors produced with PTAA as the semiconducting material and with a hole mobility of 10 −3 cm 2 V −1 s −1 have been used in ambient conditions.…”

Charge carrier transport in molecularly doped polycarbonate as a test case for the dipolar glass model

“…This particular relation has been widely used for a description of transport properties of various materials, we mention here just some recent references. [12][13][14][15][16][17][18] In some papers a comparative analysis of the data using both the GDM and DG model was carried out and it was found that the DG model provides more coherent description of charge transport. 12,16,17 Still, a proper experimental test of the DG model is far from completed.…”