THREE-DIMENSIONAL MASTER EQUATION SIMULATIONS OF CHARGE-CARRIER TRANSPORT AND RECOMBINATIO Nl IN ORGANIC SEMICONDUCTOR MATERIALS AND DEVICES FIELD OF THE INVENTION BACKGROUND This invention relates to simulation of semiconductor devices Organic semiconductors are used in various types of electronic and opto-electronic devices, such as organic light-emitting diodes (OLEDs), organic photovoltaic (OPV) devices and organic transistors. The materials used are often structurally disordered (amorphous). The electrical conductivity is a result of ’’hopping” of the electrical charges between the molecules. Due to the disorder, the energy of the charges in the molecules varies quite randomly, and the distribution of ’’hopping-rates” between each pair of molecules is quite wide. As a result, the current density is not uniform, but hlamentary. And if there are charges with opposite polarities (+ and -), as in OLEDs, the molecules at which they recombine (followed by light emission) after a mutual attraction process are not uniformly distributed. The ’’gold standard” for predictively describing these complex processes is three- dimensional kinetic Monte Carlo (3D-KMC) simulation. Within 3D-KMC simula tions, the actual positions of all charges are followed in time, taking the molecular energies, electric held and temperature into account. A disadvantage of this approach is the long simulation time. For OLEDs, obtaining a statistically correct result is at low voltages too computer-time consuming. A commonly used alternative approach,