Dilution-induced current-density increase in disordered organic semiconductor devices: A kinetic Monte Carlo study

Using three-dimensional kinetic Monte Carlo simulations, we systematically investigate the effect of dilution with an inert material on the current density in unipolar sandwich-type disordered organic semiconductor devices. Such a dilution technique was studied experimentally by Abbaszadeh et al. [Nat. Mater. 15, 628 (2016)], who observed a dilution-induced increase of the current density. The authors explained the effect as a result of a reduced density of trapped charges ("trap dilution"), assuming an exponential density of trap states. Our simulations support this explanation, and show under which conditions this trap-dilution-induced increase of the current density becomes more than outweighed by the negative effect of the dilution-induced decrease of the mobility. The effect is studied for sets of systematically varied material parameters, including systems with a Gaussian shape of the host and trap DOS.