Quantum　dot　(QD)　light-emitting　devices　operating　in　non-carrier　-injection　(NCI)　mode　have　attracted　intense　interest.　Revealing　the　source　of　carriers　that　support　the　periodic　electroluminescence　is　important　because　there　is　no　injection　of　carriers　from　the　external　electrode.　Electrons/holes　generated　by　well-to-well　multiple　ionization　in　adjacent　QDs　are　generally　recognized　as　the　carrier　source　for　electroluminescence,　and　the　stacked　QD　layers　are　necessary.　In　this　work,　NCI　electroluminescence　(NCI-EL)　from　monolayer　QDs　is　successfully　demonstrated,　which　cannot　be　properly　explained　by　the　previously　proposed　mechanism　of　multiple　ionization.　A　working　mechanism　related　to　periodic　in-well　ionization　is　proposed,　in　which　electrons　tunnel　directly　from　the　valence　band　of　QDs　to　the　conduction　band　to　form　free　electrons　and　holes.　The　effects　of　driving　voltage　amplitude,　frequency,　and　QD　size　on　the　NCI-EL　performance　are　investigated.　Finite　element　simulation　is　used　to　clarify　the　ionization　process.　We　believe　this　work　can　extend　the　working　mechanism　model　of　NCI-EL　from　QDs　and　provide　guidance　for　promoting　QD-based　light-emitting　device　performance.