Perovskite-based optoelectronic devices have gained significant attention due to their remarkable performance and low processing cost, particularly for solar cells. However, for perovskite light-emitting diodes (LEDs), non-radiative charge carrier recombination has limited electroluminescence (EL) efficiency. Here we demonstrate perovskite-polymer bulk heterostructure LEDs exhibiting record-high external quantum efficiencies (EQEs) exceeding 20%, and an EL half-life of 46 hours under continuous operation. This performance is achieved with an emissive layer comprising quasi-2D and 3D perovskites and an insulating polymer. Transient optical spectroscopy reveals that photogenerated excitations at the quasi-2D perovskite component migrate to lower-energy sites within 1 ps. The dominant component of the photoluminescence (PL) is primarily bimolecular and is characteristic of the 3D regions. From PL quantum efficiency and transient kinetics of the emissive layer with/without charge-transport contacts, we find non-radiative recombination pathways to be effectively eliminated. Light outcoupling from planar LEDs, as used in OLED displays, generally limits EQE to 20-30%, and we model our reported EL efficiency of over 20% in the forward direction to indicate the internal quantum efficiency (IQE) to be close to 100%. Together with the low drive voltages needed to achieve useful photon fluxes (2-3 V for 0.1-1 mA cm -2 ), these results establish that perovskite-based LEDs have significant potential for light-emission applications.
A new device architecture for fast organic transistor memory is developed, based on a vertical organic transistor configuration incorporating high-performance ambipolar conjugated polymers and unipolar small molecules as the transport layers, to achieve reliable and fast programming and erasing of the threshold voltage shift in less than 200 ns.
Organic–inorganic
perovskite solar cells have attracted significant attention due to
their remarkable performance. The use of alternative metal-oxide charge-transport
layers is a strategy to improving device reliability for large-scale
fabrication and long-term applications. Here, we report solution-processed
perovskite solar cells employing nickel oxide hole-extraction layers
produced in situ using an atmospheric pressure spatial atomic-layer
deposition system, which is compatible with high-throughput processing
of electronic devices from solution. Our sub-nanometer smooth (average
roughness of ≤0.6 nm) oxide films enable the efficient collection
of holes and the formation of perovskite absorbers with high electronic
quality. Initial solar-cell experiments show a power-conversion efficiency
of 17.1%, near-unity ideality factors, and a fill factor of >80%
with negligible hysteresis. Transient measurements reveal that a key
contributor to this performance is the reduced luminescence quenching
trap density in the perovskite/nickel oxide structure.
High performance organic field-effect transistor nonvolatile memory is achieved by integrating gold nanoparticles and graphene oxide sheets as the hybrid nano-floating-gate. The device shows a large memory window of about 40 V, high ON/OFF ratio of reading current over 104, excellent programming/erasing endurance, and retention ability. The hybrid nano-floating-gate can increase the density of charge trapping sites, which are electrically separate from each other and thus suppress the stored charge leakage. The memory window is increased under illumination, and the results indicate that the photon-generated carriers facilitate the electron trapping but have almost no effect on the hole trapping.
Articles you may be interested inHigh-performance, low-operating voltage, and solution-processable organic field-effect transistor with silk fibroin as the gate dielectric Appl. Phys. Lett.
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