I am trying to simulate electronic devices with sharp interfaces such as bilayer organic solar cells and diodes under the high applied voltage regimes to study the physics of their breakdown. There are steep gradients of important quantities, such as charge concentrations and electric potential, at the interfaces which causes the Scharfetter-Gummel finite difference method to become unstable. I have found that reducing the mesh size does not significantly help. What are possible alternative methods which would be stable and accurate?