Deep-red and near-infrared light-emitting electrochemical cells employing perovskite color conversion layers with EQE >10%

Solid-state light-emitting electrochemical cells (LECs) exhibit high potential for application in consumer electronics due to their promising advantages of solution-processable simple device architecture, low-voltage operation, and compatibility with inert metal electrodes. However, low device efficiencies of deep-red and near-infrared (NIR) LECs hinder their application since long-wavelength organic emissive materials commonly suffer from moderate emission efficiencies. To improve the device efficiencies of deep-red and NIR LECs, combinational devices by integrating efficient blue-green LECs employing an ionic transition metal complex with perovskite color conversion layers are demonstrated. Saturated deep-red and NIR output emission can be generated through energy down-conversion. Furthermore, the light extraction enhancement technique based on a diffusive layer beneath the indium-tin oxide layer is utilized to boost the device efficiency. Both the optical simulation and experiments confirm doubled light output via the aid of such a diffusive layer. These combinational devices deliver saturated output emission peaks at 640, 672, and 700 nm with a narrow full width at half maximum <40 nm and high external quantum efficiencies >10%. These device efficiencies are among the highest reported values for deep-red and NIR LECs. This work shows an alternative way to overcome the limitation of low emission efficiencies for long-wavelength organic emissive materials and thus successfully realizes efficient deep-red and NIR LECs.