| Amorphous silicon/crystalline silicon (a-Si/c-Si) heterojunction solar cells offer high efficiency in a simplified and easily scalable process. Despite success in commercialization of these devices, the detailed working principles of them are poorly understood. In particular the effect of interface defects at the a-Si/c-Si heterojunction and the intervening intrinsic layer require explanation. The goal of this research is to understand the effect of interface defects and the intrinsic layer on non-linear effects in current-voltage curves of heterojunction devices by developing a computer model in SENTAURUS.;Previously, computer models based in programs such as PC1D, AFORSHET and AMPS-1D have been used but suffer from drawbacks such as not including the gap states and interface modeling as well as not having the option of user-defined recombination statistics. In this work the commercial package SENTAURUS is used, providing a robust and reliable environment in which to develop the model. Key features of the model are the inclusion of dangling bond states via a defect pool model, band gap narrowing of the a-Si, region specific recombination-generation statistics and the change in capture cross section due to charging of trap states.;Simulation of devices using this model has demonstrated several processes which guide for device design. Firstly, the number and nature of defects at the a-Si/c-Si interface influence device behavior strongly. More importantly, the thickness of the intrinsic layer is found to be critical. Under ideal operating conditions a p-type region is induced in the intrinsic layer leading to the p-n junction being formed in the c-Si.;When the intrinsic layer thickness is increased this is no longer the case, with the p-n junction forming in the a-Si, leading to drastically reduced performance of the device. The development of the recombination models, their incorporation into SENTAURUS, the modeling results and the implications for device design allow improved heterojunction solar cell designs. |
