Charge transport properties for carbazolyl groups pendant poly(glutamate)

Abstract

Carbazolyl groups pendant poly(glutamate) (PCLG) was prepared to analyze its charge‐transport properties by employing mobility measurements and thermally‐stimulated current (TSC) measurements. The mobility induced TSC (MITSC) model proposed by I.Chen was employed to evaluate the experimental TSC spectra with mobility results. Simulated MITSC spectra showed good agreement in its peak temperature with experimental TSC spectra for PCLG. This suggests that the carrier transport followed the trap‐limited mechanism estimated by the mobility results. Further, the peaks in experimental TSC spectra appeared over the same temperature range as that in thermally‐stimulated polarization current (TSPC) spectra. Since the TSPC spectra were found to be correlated with the dielectric tan δ spectra for PCLG, the peaks in TSPC spectra are attributed to the side‐chain relaxation for PCLG. Therefore, the similarity between TSPC and TSC spectra indicates that the charge‐transport mechanism for PCLG was considerably affected by side‐chain relaxation for PCLG, which would vary the energy state of trap sites and effectively reduces the energy for the release of the carriers trapped on the illuminated surface. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 61–69, 1999

Charge transport properties of triphenylamine-pendant polypeptide

“…The fair agreement, however, suggests that the experimental TSC spectrum of PATPA can be evaluated with the parameters of Gill's equation obtained from the mobility measurement. The difference in the rise to the peak temperature between the MITSC and the experimental TSC would be due to the wide distribution of the mobility of carriers in the polymer film, and its explanation has been given in the paper reported earlier 7. The peak temperature in the TSC spectrum of PATPA is lower than that of PVK and PCLG, supporting the fact that the mobility of PATPA is higher than that of PVK and PCLG.…”

“…The PCLG film showed emission peaks assignable to the second and the sandwich excimers. The average intersite distance between carbazole groups along the PCLG chain is about 10 Å and the fluctuation of the intersite distances is affected by the side chain configuration 7. The appearance of the emission from excimer sites is understandable.…”

“…In trap‐limited hopping charge transport mechanism, the mobility (μ) in the film is expressed by using the average intersite distance d as follows:7 where A is a constant, and γ is the wave‐function overlap factor. The average distance between planer carbazolyl groups in a PVK and a PCLG chain was calculated as 6.6 Å and 10 Å, respectively.…”

Investigating Side Chain Mediated Electroluminescence from Carbazole-Modified Polyfluorene

“…To investigate if any possible stacking of Cz groups in Cz100PF occurs and how the stacking affects its charge transport characteristics, we compare Cz100PF with poly(vinyl cabazole) (PVK) on their charge trapping characteristics. Previous studies indicated the presence of two kinds of excimers in PVK, the partially overlapped excimer and the face-to-face excimer, both acting as hole-trapping sites . Figure a shows photoexcited thermally stimulated current (PE TSC) 12a,c profiles of unmodified PF (PFO), Cz100PF, and PVK.…”

Multicolor single‐layer electroluminescence device using poly(L‐glutamate) for hole transport

“…It has been reported that in a LC cell, PCELG has a high mobility of $10 À3 cm 2 /V s. This is higher than those for amorphous PCELG (10 À8 cm 2 /V s) and PVCz films (10 À7 cm 2 /V s) by about 4-5 orders of magnitude. [6][7][8][9] Consequently, highly ordered intra-and interchain structures are considered to improve photoconductivity and charge carrier transport.…”