We report strong surface plasmon polariton mediated transfer of energy between molecular excitons across the metallic cathode of an electrically-pumped organic heterostructure. The donor molecular excitons at the organic heterojunction resonantly excite surface plasmon modes on both sides of the optically thick metal electrode, which evanescently couple to dye molecules near the electrode's exterior surface. Dye fluorescence in the capping layer on the exterior of the device shows a 6.5-fold increase in intensity due to this effect, far exceeding any enhancement attributable to Purcell or optical microcavity effects. Demonstration of this energy transfer mechanism for electrically-pumped excitons suggests new sensing and imaging applications with high signal to noise ratio and new routes for performance improvement in energy harvesting devices, plasmonic devices, and organic LEDs (including white light emission).