Simulation of a complete PV system shall stem from a Multiphysics perspective. Within a continuum modeling approach, among these physics, the thermal model of a PV panel is most crucial because all the other models are directly or indirectly related to it. As all models of a PV system are connected sequentially, error from one model component propagates to the next model component and the overall system error accumulates eventually. One of the main objectives of this work was to increase the prediction accuracy by developing a fully transient 2-D finite difference (FD) based thermal model. The developed computational code is completely generic and can be applied to any type of PV technology or configuration. It was shown in the study how to choose an appropriate grid size for any FD model. Using the developed code, various studies were also conducted. Modified radiation models, heat transfer coefficients and thermal networks for the PV panel were proposed in the study, which remarkably improved the accuracy of the thermal model. Also studied were the effects of including heat transfer from the sides of a PV panel and heat generation in the front glass cover. The results showed that ignoring the heat transfer from the sides of a PV panel and including heat generation in the front glass cover have no noticeable difference in the model prediction.