The Electrostatic Potential analysis object can only be computed for Bulk and Molecule Configuration, see
https://docs.quantumwise.com/manual/Types/ElectrostaticPotential/ElectrostaticPotential.html.
For Device Configuration, you may compute Electrostatic Difference Potential , see
https://docs.quantumwise.com/manual/Types/ElectrostaticDifferencePotential/ElectrostaticDifferencePotential.html, or actually Hartree Difference Potential energy if you see changes in the electrostatic potential energy.
If you have computed the potential energy for the entire system and different sub-systems of your molecular junction, then you may visualize the potential change by computing dE = E(entire system) - E(sub-system 1) - E(sub-system 2) - ... . The 2 subsystems can be, for instance, the electrodes without the molecules (this should be done using the same device configuration, just remove the molecule) and the molecule without electrodes (you have to use bulk configuration with the unit cell size as that of the central region of the device, and use the multigrid Poisson solver with the Dirichlet and Neumann boundary conditions imposed on the left and right side of the slab, respectively).
To compute the dE, you can use Grid Operation plugin available in the QuantumATK NanoLab, just select all the potential objects on the LabFloor and click on Grid Operation on the left panel of the GUI.
The visualization of the new grid object can be done in the Viewer, and you may also drag-and-drop the configuration from the LabFloor to the Viewer to superimpose the potential and the atomic structure of the molecular junction.
Note that the same operation can be done for electron density or any object on the real-space grid.
