High external quantum efficiencies of above 30% in blue phosphorescent organic light-emitting diodes are demonstrated by Jun Yeob Lee and Chil Won Lee on page 5450 using novel pyridoindolebased bipolar host materials. This is the first work reporting above 30% external quantum efficiency in blue organic light-emitting diodes and opens a way to enhance the external quantum efficiency of blue organic light-emitting diodes up to a theoretical limit of 40%.
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The spontaneous formation of ripples in molybdenum disulfide (MoS2) monolayers is investigated by Pere Miró and co-workers on page 5473 via density-functional-theory-based tight-binding Born–Oppenheimer molecular dynamics. Monolayers with different lengths show spontaneous rippling during the simulations. The density of states reveals a decrease in the bandgap induced by the stretching of the MoS2 units due to ripple formation. Ripples in the MoS2 monolayers have an effect on the properties of the material and may impact its application in nanoelectronics.
The electrochromism and photothermoelectric properties of a poly(3,4-ethylenedioxyselenophene) derivative are investigated by precisely controlling the morphology and applied electrical potential of the flexible polymer films. On page 5483, Eunkyoung Kim and co-workers report a highly efficient and flexible photothermoelectric converter using doped poly(3,4-ethylenedioxyselenophene)s. Efficient visible to near-infrared absorption, photon to heat, and heat to electric conversion are realized in one polymer film.