A kinetic Monte Carlo study of defect assisted transport in silicon heterojunction solar cells

The device performance of an amorphous silicon (a-Si)/crystalline silicon (c-Si) solar cell depends strongly on the interfacial transport properties of the device. The energy of the photogenerated carriers at the barrier strongly depends on the strength of the inversion at the heterointerface and their collection requires interaction with the defects present in the intrinsic amorphous silicon buffer layer. In this work we present a theoretical model to study the defect assisted transport of photogenerated carriers through the intrinsic amorphous silicon barrier. We implement the kinetic Monte Carlo (KMC) method which allows us to simulate the interaction of discrete carriers with discrete defects. This method allows us to study defect transport which takes place on a time scale which is too long for traditional ensemble Monte Carlo's to analyze. We analyze the injection and extraction of carriers via defects by calculating transition rates, i.e. probability of transition to defect states within the intrinsic amorphous silicon barrier. The KMC results allow us to quantitatively study the properties of the heterointerface barrier in terms of how it affects transport.