The applicability of the transport-energy concept to various disordered materials

Abstract

It is known that in disordered semiconductors with purely exponential energy distribution of localized band-tail states, as in amorphous semiconductors, all transport phenomena at low temperatures are determined by hopping of electrons in the vicinity of a particular energy level, called the transport energy. We analyse whether such a transport level exists also in materials with densities of localized states (DOSs) different from the purely exponential one. We consider two DOS functions g( ) ∼ exp{−( / 0 ) λ } with λ = 2, typical for polymers, heavily doped semiconductors, and, probably, liquid semiconductors and λ = 1 2 , typical for mixed crystals. It is shown that in both cases the transport energy exists, implying that it also exists for all intermediate forms of the DOS. Special attention is paid to the dependences of the transport level and of its width on the DOS parameters and temperature.

Temperature dependence of the charge carrier mobility in disordered organic semiconductors at large carrier concentrations

“…Eq. ͑6͔͒ ͑this conclusion is also supported by previous studies [28][29][30] ͒ and it shifts toward deeper tail states of the DOS distribution with further lowering temperature, 21 so it eventually approaches the Fermi level F which features a much-flattened temperature dependence. This is depicted in the Fig.…”

Scaling of current distributions in variable-range hopping transport on two- and three-dimensional lattices

“…that this concept is only useful for hopping in band tails with densities of states that decay fast enough as a function of energy. 32 Hence, the concept is inapplicable to the situation of a constant density of states, as considered here. Furthermore, our definition Eq.…”

Predictive modeling of the current density and radiative recombination in blue polymer-based light-emitting diodes

“…Experimental 1 and theoretical [2][3][4][5][6][7][8][9] studies have made clear that the resulting energetic disorder of the states in between which the charge carrier hopping takes place does not only determine the temperature (T) and electric field (F) dependence of the mobility, 10 but that it also gives rise to a charge carrier density (n) dependence. Although various advanced numerical OLED device models have been developed and applied, [11][12][13][14][15][16][17][18][19][20][21][22][23][24] so far analyses of the current density and radiative recombination in full OLEDs, taking the carrier density dependence of the mobility into account, have not yet been reported.…”