Coordinating electron transport and layer thickness enhances electrochemiluminescence in solid-state emitters

Electrochemiluminescence (ECL) efficiency critically depends on electron transport within the light-emitting layer, yet the interplay between electron diffusion length and emitter thickness remains underexplored. Here we synthesized carbon nitride photoelectrodes with tunable thicknesses to systematically investigate this relationship. By defining the ratio of electron diffusion length (Ln) to light-emitting layer thickness (d), we identified an optimal Ln/d range (~0.9-1.2) that maximizes ECL performance by balancing the dynamic competition among bulk electron transport and interfacial reactions. This coordination enhances electron availability and mass transfer, leading to record-high ECL efficiencies in carbon nitride systems. The universality of this strategy was confirmed across diverse ECL materials, including metal-organic frameworks and silver nanoclusters. These findings provide a quantitative descriptor for designing efficient solid-state ECL emitters by dynamically tuning emitter thickness to match intrinsic electron transport properties, advancing the development of highperformance ECL devices.