To reduce cost and improve environmental sustainability, there continues to be an important need for the development of efficient organic light‐emitting diodes (OLEDs) that do not rely on heavy metal‐containing compounds. In particular, the efficiency of fluorescent near‐infrared (NIR) OLEDs continues to lag well‐behind that of their platinum‐containing counterparts. Low efficiencies in this spectral range mainly arise from the low quantum yields of fluorescent NIR emitters due to the energy gap law and inefficient harvesting of triplet excitons. In this paper, a thermally activated delayed fluorescent (TADF) material is used as the assistant dopant to demonstrate pure NIR‐emitting fluorescent OLEDs with an external quantum efficiency of up to 3.8%, with an electroluminescence maximum at 840 nm and a spectral full‐width at half‐maximum of < 40 nm. The efficiency is more than three times higher than that of the best previously reported fluorescent OLEDs in this spectral range and approaches that achievable with the best platinum‐containing phosphorescent emitters.

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The transport distance of excitons in exciton-polariton systems has previously been assumed to be very small ( 1 µm). The sharp spatial profiles observed when generating polaritons by nonresonant optical excitation show that this assumption is generally true. In this paper, however, we show that the transport distances of excitons in two-dimensional planar cavity structures with even a slightly polaritonic character are much longer than expected (≈ 20 µm). Although this population of slightly polaritonic excitons is normally small compared to the total population of excitons, they can substantially outnumber the population of the polaritons at lower energies, leading to important implications for the tailoring of potential landscapes and the measurement of interactions between polaritons.

In this investigation of the roles of 2 different dimensions of mood (pleasantness and arousal) in mood-dependent memory (MDM), participants generated words while listening to a selection of independently rated mood music (normative study and Experiment 5). Then they recalled the words while listening to another mood-music selection (Experiments 1-3) or to a verbal-mood scenario (Experiment 4). Changing only the dimension of mood pleasantness from generation to recall decreased memory whether the intended moods were explicitly defined or not. However, changing only arousal decreased memory only when moods were defined. Thus, pleasantness-dependent memory, but not arousal-dependent memory, occurred consistently. Although MDM also occurred with simultaneous changes in both dimensions, the effect was not significantly greater than that of pleasantness-dependent memory. The results are discussed in terms of 2-dimensional theories of emotion as applied to memory.

We present a study of the macroscopic dynamics of a polariton condensate formed by non-resonant optical excitation in a quasi-one-dimensional ring shaped microcavity. The presence of a gradient in the cavity photon energy creates a macroscopic trap for the polaritons in which a single mode condensate is formed. With time-and energy-resolved imaging we show the role of interactions in the motion of the condensate as it undergoes equilibration in the ring. These experiments also give a direct measurement of the polariton-polariton interaction strength above the condensation threshold. Our observations are compared to the open-dissipative one-dimensional Gross-Pitaevskii equation which shows excellent qualitative agreement.