Overlapping, dangling sp3-hybridized orbitals are typical for hydrocarbons exhibiting an alternating bonding structure. These orbitals might either interfere constructively with p-conductive bonding or destructively with n-conductive antibonding bands. In each case the resulting conduction band can be imagined as a branched wave function spreading across the sigma-bound molecular skeleton. Charges are transported along these bands by thermally activated, incoherent tunneling events. The technological relevance of pi-conjugated plastics arises from their simple and cheap processability as compared to silicon. Moreover, the fabrication of optoelectronic devices made of plastics is more ecological. Organic thin-film transistors, light-emitting diodes, lasers, and photovoltaic applications have already been fabricated so far. However, many of these novel device architectures suffer from severe technical problems, like that of low carrier mobility and/or effects due to elusive device physics at bulk heterojunctions or metal interfaces. Consequently the development of an efficient, generally applicable and precise software to predict promising materials and assemblies is indispensable. The insights gained by computer experiments govern the fabrication of prototypes, in this way shortening the developmental period remarkably. A three-dimensional kinetic Monte Carlo simulator covering heterojunctions, molecular doping, metal interfaces, image charge effects, interband transitions and arbitrary space charge accumulations has been developed, tested, and optimized. Baessler's Gaussian disorder model forms the computer program's conceptual and theoretical basis. For calibration, the dark current characteristics of zinc phthalocyanine have been used. The electrostatic potentials are updated after each charge transfer. Organic optoelectronic devices are usually contact-dominated. Thus the development focused on the unified description of hopping injection, conduction, and recombination and extraction of carriers.