Non-doped OLEDs employing TADF conjugated polymers exhibit excellent electroluminescent performances.

Suppressing emission quenching is still a real issue for thermally activated delayed fluorescence (TADF) materials as the emitters generally tend to aggregate in condensed film, leading to deteriorating performance in devices. In contrast to the TADF small molecules adopting host–guest systems, polymers possess the advantage that the TADF chromophore can be chemically dispersed into the backbone and thus the quenching process can be inhibited effectively. Here, a strategy applied to the conjugated polymer is presented, in which a TADF chromophore with controlled content is embedded into the backbone of polycarbazole through its donor moiety. The oligomeric carbazole segment acts as the role of “blocking segment,” suppressing the intra‐ and interchain interactions. The polymers therefore exhibit superior photoluminescence quantum yield of up to 92.1%. More importantly, the efficiency roll‐offs of the relevant devices are significantly reduced, offering an external quantum yield (EQE) of 15.6% even at luminance of 1000 cd m−2, corresponding to 92.3% to the maximum EQE.

Solution-processed organic light-emitting diodes (s-OLED) consisting of TAPC/TmPyPB interfacial exciplex host and polymer PAPTC TADF emitter are prepared, simultaneously displaying ultralow voltages (2.50/2.91/3.51/4.91 V at luminance of 1/100/1000/1000 cd m), high efficiencies (14.9%, 50.1 lm W), and extremely low roll-off rates (J of 63.16 mA cm, L of ca. 15000 cd m). Such performance is distinctly higher than that of pure-PAPTC s-OLED. Compared to pure-PAPTC, the advanced emissive layer structure of TAPC:PAPTC/TmPyPB is unique in much higher PL quantum yield (79.5 vs 36.3%) and nearly 4-fold enhancement in k of the PAPTC emitter to 1.48 × 10 s.

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Intrinsic compatibility of exciplex couple determines the EL performance of the resultant solution-processed phosphorescent OLEDs, particularly driving voltage behaviours.

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Barium strontium zirconate titanate ceramics ((BaSr)(ZrTi)O 3 -BSZT) with Zr 4+ ionic contents of 15 and 20 mol % and Sr 2+ ionic contents of 15, 20, 25, and 30 mol % were prepared using a solid-state reaction approach. X-ray diffraction and scanning electron microscopy were used to characterize the lattice structure and morphologies of the ceramics. Permittivity and polarization as a function of temperature were characterized using an impedance analyzer and a Tower−Sawyer circuit. The electrocaloric effect was measured directly and calculated using the Maxwell relation (indirectly). The results indicated that the BSZT ceramics change from a normal ferroelectric to a relaxor ferroelectric with increasing Zr 4+ ionic content, which can be further modified by the addition of Sr 2+ ionic content. The optimized adiabatic temperature change ΔT obtained is 2.43 K in (Ba 0.85 Sr 0.15 )(Zr 0.15 Ti 0.75 )O 3 ceramics, and ΔT >1.6 K over a wide temperature span of 120 °C was obtained.