Novel approach to the Dember effect

In this paper it is demonstrated that the precise physical nature of the Dember effect is a concentration gradient of nonequilibrium carriers under nonuniform illumination. We used the fact that any photo‐EMF (electromotive force) can only exist in the presence of nonequilibrium charge carriers, when there are two different Fermi quasilevels. That is why the Dember EMF (as the photo‐EMF of any nature ) is not identified as a voltage drop arising between the device contacts in open circuit. Moreover, a correct definition of the EMF is only possible if the problem is solved in a closed circuit. It is shown that the Dember EMF does not depend on the difference of electron‐to‐hole diffusion coefficients and it is not linked to ambipolar diffusion. Additionally, it is found that the sign of the EMF depends on the ratio between the recombination rates on the contacts, which can be detected from the spectral characteristic of the Dember EMF. image