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Mechanisms of nanoglass ultrastabilit

Although the relative changes of the layer density are typically in the range of 1 to 2%this subtle difference will likely influence the excitonic properties significantly because all couplings and transfer processes come with nanoscale sensitivity The TPBi layer is the host for the green emitter in the G0 devices, in which the 8 wt % doping of Ir(ppy)2(acac) is assumed to not influence the glassy matrix properties decisively. To test the hypothesis that the changes in stability and molecular packing of TPBi cause the enhanced efficiencies, we used the same device architecture with three additional phosphorescent emitters [Ir(MDQ)2(acac), Ir(ppy)3, and FIrpic].shows how the EQE is enhanced when the temperature is set to 66°C for the devices R1, G1, and B1, using the red, green, and blue emitter, respectively. These results further support the idea that the host (TPBi) properties are the ones affecting the device performance. Looking at the increase of the PL decay times τeff of +8% (G0), +17% (R1), +15% (G1), and +29% (B1) in fig. S1  (G to I), with the assumption that the cavity influence, due to constant device thickness, and the radiative rate stay constant one can relate the transient time enhancement directly to an improved radiative efficiency due to reduced nonradiative rates. The origin of this reduction can be manifold: Either it is related to reduced excitonic trap states in the bulk of the EML or it could be rationalized in terms of a possible suppression of the β-relaxation—molecule vibrations within a cage formed by its neighbors—in the ultrastable glass of TPBi, which could slow down the nonradiative phonon-mediated monomolecular thermal relaxation processes (5455). Similar observations of reduced nonradiative recombination rates have been observed in polymer-based systems that were prepared in a very rigid form that led to a higher packing density compared to a conventionally fabricated reference sample