The first LEC consisted of a conjugated polymer (CP) as an organic semiconductor emissiver19, and the current state-of-the-art CP-LEC offers an efficiency of 14.6 cd A-1 with a luminance of 112 cd m−2.22 Note that we only consider ratios with a luminance greater than 100 m cd-2, as we focus on achieving practical LECs with high luminance with high efficiency. The second major class of LEC components includes a transition metal ion complex (iTMC) as emissive organic semiconductors, and since this group of materials can harvest both singulant eccentrics and triplet eccentrics, the efficiency ceiling is higher23. One of the general problems with iTMC LECs is that the characteristic long service life of the triplet excitton leads to a long diffusion distance for mobile triplets, which, combined with a high concentration of polarons, results in a strong eccentric-polarone deterrent. The best iTMC-LEC performance to date, an electrical efficiency of 28.2 cd A-1 with a brightness of 750 cd m-2, was achieved thanks to a non-stationary pulse current transmission24, while traditional bias continuous driving results in lower peak power25,26,27,28,29. Large-scale LECs were manufactured by internal spraying under ambient air. The original active interior was diluted to 80% tetrahydrofuran and sprayed on a glass substrate pre-presented at the ITO (Thin Film Devices, US), held at 70°C by a hob. Spray catchment was carried out with a self-developed and computer-controlled spray box (LunaLEC AB, Sweden), equipped with an internal mixed nozzle. N2 gas printing was adjusted to 450 × 103 Pa and the ink input rate was 1 ml min-1. The nozzle was programmed to move back and forth over a range of 10 × 10 cm2 at a height of 6 cm above the substrate and stop after 8 completed scans (t = 190 s). The resulting thick dry active material layer was 350 nm. The al-high electrode was cut by thermal evaporation by a shaded mask, thus defining the emission surface from 67 × 67 mm2. The luminance was measured using a luminance measuring device (LS-110, Konica) and the luminance presented is the average of more than six measurements at different geographical locations above the surface of the device. The photo was taken by a digital camera (Canon EOS 300D) with an exposure time of 1/120 s and an f/2.2 diaphragm.
The problem of eccentric-polaron deterrence has been effectively addressed in OLEOs emitting triplets through the design of a sophisticated apparatus architecture comprising a variety of different layers, with each layer having a specific task and having a precise thickness at the nm30,31 level. The sending central layer is of a host-guest character where the eccentric is caught on a guest emitting triplets. This complex and exact device architecture is manufactured by sequential high vacuum steam and is therefore not compatible with the simplicity of the LEC concept. Nevertheless, a number of recent trials with much simpler leC docking architectures have resulted in a large number of transmit colors, none of these devices has an efficiency of 10 cd A-1 for a luminance greater than 100 cd m-2 in stationary mode32,33,34,35,36,37,38,39,40,41,42,43,44,45,46. . . .