The effect of the thickness of a buffer layer of intrinsic GaSe oxide on the electrical, photoelectric, and emissive properties of ITO-GaSe heterojunctions is studied. It is established that the introduction of a Ga2O3 layer with thickness as large as 5–6 nm into the ITO-GaSe heterojunction results in a change in the current-flow mechanisms in the structure, an increase in the open-circuit voltage V oc by more than twofold (in this case, the situation where the V oc exceeds appreciably the contact potential difference is realized), an increase in the electroluminescence intensity by more than an order of magnitude, and an increase in the efficiency of photoconversion by more than two times compared to samples where the Ga2O3 layer was not grown intentionally.