Study on the Diffusion Rate of the Charge Carrier Transport in Regio-Random and Regio-Regular P3HT

Abstract

Muon spin relaxation experiment has been conducted to probe the hopping mechanism in the poly(3-hexylthiophene-2,5-diyl) (P3HT) for both types of regio-random (Rdm) and regio-regular (RR). In this study we have performed calculations over the collected data to obtain the parallel and perpendicular diffusion rates, at temperatures of 10 K and 300 K. The calculation is based on the fitting method to the empirical function that relates the relaxation rate with the diffusion rates. For Rdm-P3HT, we have obtained the parallel diffusion rate to be 5.43 x 1013 rad/s at 300 K and 4.90 x 1014 rad/s at 10 K. While the perpendicular diffusion rates are 5.29 x 108 rad/s at 300 K and 1.88 x 106 rad/s at 10 K. For RR-P3HT, we have obtained the parallel diffusion rate to be 1.04 x 1014 rad/s at 300 K and 1.28 x 1015 rad/s at 10 K. While the perpendicular diffusion rates are 6.10 x 108 rad/s at 300 K and 5.35 x 105 at 10 K. The diffusion rates of RR-P3HT are higher than that of Rdm-P3HT, especially in the parallel direction. In both types of material, the parallel diffusion rate decreased with temperature, while the perpendicular diffusion rate increased with temperature, showing a change of behavior from 1D to 3D direction of charge transport.

Effect of Light Irradiation on the Diffusion Rate of the Charge Carrier Hopping Mechanism in P3HT–ZnO Nanoparticles Studied by μ+SR

“…These results are consistent with our proposed model regarding the change in dimensionality obtained from the H LF dependence of λ 1 as described in Figure 4. When comparing the diffusion rate with that for regio-regular P3HT without ZnO nanoparticles, we found that the parallel diffusion rate in the present study was of the same order of magnitude, while the perpendicular diffusion rate was two orders of magnitude higher in the high-temperature range [32]. Moreover, compared with those of other conjugated polymers such as polyaniline (PANI), polypyridine, and polyphenylenevinylene (PPV), the parallel diffusion rates of regioregular P3HT-ZnO nanoparticles are higher by up to three orders of magnitude, and the perpendicular diffusion rates are slightly higher than those of PANI and PPV at high temperature [41,42].…”

“…where ω = γH, γ are gyromagnetic ratios, ρ is the spin density, Ω z and Ω + are geometrical factors that are related to the scalar and dipolar hyperfine coupling parameters, and f (ω) is the spectral density of the spin correlation function as previously reported for calculating the diffusion rate in polymer samples, as shown in Equation ( 5) [31][32][33].…”

“…The values of the parameters used in the calculation are ρΩ z = (150 MHz) 2 , Ω + /Ω z = 14, γ µ = 135.5387 MHz/T, and γ e = 28, 024.95164 MHz/T [30][31][32][33].…”

“…By analyzing the µ + SR spectra, the hopping mechanism and the diffusion rate of the charge carriers in the sample can be calculated. The calculation and analysis were based on an empirical function using the equations relating to the relaxation rate data as a function of the H LF with the diffusion rates [30][31][32][33]. This paper is organized as follows: Section 1 is an introduction describing the state of the diffusion rates and the reason for choosing the regio-regular P3HT-ZnO nanoparticles as the material to be investigated.…”