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A Monte Carlo model of carrier separation and recombination in nanostructured organic photovoltaic (OPV) devices which takes into account all electrostatic interactions, energetic disorder, and polaronic effects is presented. The model predicts that an idealized interdigitated morphology could double the carrier collection efficiency achieved in a blend and also suggests that the maximum power output is extremely sensitive both to the geminate recombination rate across the heterojunction and to carrier mobility.

Both alloy composition and avalanche region width have significant effects on the temperature dependence of breakdown voltage. Monte Carlo simulations show that alloy scattering reduces the temperature dependence of breakdown voltage, the effect is too small to account for the observations.

We use a Monte Carlo model to predict the effect of composition, domain size, and energetic disorder upon the mobility of carriers in an organic donor-acceptor blend. These simulations show that, for the changes in local morphology expected within the thickness of a typical bulk heterojunction photovoltaic device, changes in mobility of more than an order of magnitude are expected. The impact of nonuniform mobility upon space-charge-limited diode and photovoltaic (PV) device performance is examined using a drift-diffusion model. The current passing through a space-charge-limited diode is shown to depend upon the position of the layers with differing mobility. Accurate modeling of the current in such devices can only be achieved using a drift-diffusion model incorporating nonuniform mobility. Inserting a 20 nm thick layer in which the mobility is less by one order of magnitude than in the rest of the 70 nm thick PV device reduced the device efficiency by more than 20%. Therefore it seems vital to exert a high degree of control over the morphology throughout the entire blend PV device, otherwise potential PV performance may be lost. [ABSTRACT FROM AUTHOR]

A simple Monte Carlo model is used to simulate the avalanche process in a multiplication region which incorporates a heterojunction, intended to introduce localization into the ionization process and reduce excess avalanche noise. The results are compared with those of models where the ionization path length distribution is represented by an exponential decay, displaced from the origin by a ballistic dead space. While the latter results depend sensitively on the arbitrary choice of scheme used to evaluate the model parameters, they agree remarkably well with Monte Carlo, considering the simplicity of the model. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Avalanche breakdown voltage has been measured in a series of AlxGa1-xAs (0