Charge transport Monte-Carlo simulations

Bassler H (1993) Charge transport in disordered organic photoconductors - a Monte-Carlo simulation study. Phys Status Solidi B 175 15... 

To model the carrier transport within the space-charge field of GaAs(lOO) more accurately, a full ensemble Monte Carlo simulation has been conducted (Zhou et al.,... 

H. Bassler, Charge transport in disordered organic photoconductors a monte carlo simulation study, Phys. Status Solidi B, 175, 15-56 (1993). 

Monte Carlo simulation shows that, although the local one-dimensional feature of charge transport limits the intrinsic hoping, the doping dramatically increases the mobility as a result of the spatial occupation of insulating matrix that dilutes the dopant anions and weakens the Coulomb interaction. 

Abstract This topic reviews random walk Monte Carlo simulation models of charge transport in DSSC. The main electrmi transport approaches used are covered. Monte Carlo methods and results are explained, addressing the continuous time random walk model developed for transport in disordered materials in the context of the large number of trap states present in the electron transporting material. Multiple timescale MC models developed to look at the morphology dependence of electron transport are described. The concluding section looks at future applications of these methods and the related MC models for polymer blend cells. 

Monte Carlo simulations of charge transport in organic semiconductors have a long history, including the pioneering work of Bassler [1] which allowed the characteristics of the macroscopically measured mobility to be related to... 

One of the easiest ways to model charge transport in a random distribution of localized states is via Monte Carlo simulation [7, 8]. The essential input parameter is the width a of the DOS, which is usually assumed to be of Gaussian shape ... 

The relation between the conductivity and the trap concentration is shown in Fig. 12. The numerical values of the occurring parameters are M = 10 2cm-. To = 1,000 K, 7i = 500 K, d = —0.2 eV, a = 6 nm , the temperature is T = 400 K, and Oo = 1 X lO Sm- At a critical trap concentration, the conductivity has a minimum. This has been verified by experiments [27] as well as Monte-Carlo simulations [28]. The minimum is due to the onset of inter-trap transfer that alleviates thermal detrapping of carriers, which is a necessary step for charge transport. We can also see that a small trap concentration has virtually no effect on the conductivity. 

The Monte-Carlo simulation of these models reproduces well the charge carrier transport properties in the mesophases, i.e., the mobility independence of both temperature and electric field in the temperature above room temperature, if a small sigma (40 60 meV) is taken for the Gaussian width of the distribution of localized states in Eq. (2.2). In this equation p, is the mobility, a is the Gaussian width of the distributed energy states for hopping sites, E is an index of the positional disorder, k is the Boltzman constant, T is the temperature, E is the electric field and C is a constant. The constants a and n depend on the type of mesophase, e.g., 0.8 and 2 for the SmB phase and 0.78 and 1.5 for the SmE phase, respectively. This value of cr (40-60 meV) is half that for typical amorphous solids [61]. 

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