The harvesting of ‘hot’ triplet excitons through high-lying reverse intersystem crossing mechanism has emerged as a hot research issue in the field of organic light-emitting diodes. However, if high-lying reverse intersystem crossing materials lack the capability to convert ‘cold’ T₁ excitons into singlet ones, the actual maximum exciton utilization efficiency would generally deviate from 100%. Herein, through comparative studies on two naphthalimide-based compounds CzNI and TPANI, we revealed that the ‘cold’ T₁ excitons in high-lying reverse intersystem crossing materials can be utilized effectively through the triplet-triplet annihilation-mediated high-lying reverse intersystem crossing process if they possess certain triplet-triplet upconversion capability. Especially, quite effective triplet-triplet annihilation-mediated high-lying reverse intersystem crossing can be triggered by endowing the high-lying reverse intersystem crossing process with a ³ππ*→¹nπ* character. By taking advantage of the permanent orthogonal orbital transition effect of ³ππ*→¹nπ*, spin–orbit coupling matrix elements of ca. 10 cm⁻¹ can be acquired, and hence ultra-fast mediated high-lying reverse intersystem crossing process with rate constant over 10⁹ s⁻¹ can be realized.

In this work gold nanoparticles (Au NPs) are incorporated into a PEDOT:PSS layer, resulting in ∼4.0 fold enhanced fluorescence emission of a CH₃NH₃PbBr₃ film. Through experiments and theoretical simulation, we first demonstrated that the enhancement comes from the simultaneous near- and far-field effects of Au NP enhanced perovskite fluorescence.

Solution-processed organic–inorganic halide lead perovskites have attracted increasing attention due to their great potential in low-cost, effective, and versatile light emission applications and large-scale portable optoelectronic devices. In this paper, formamidinium lead tribromide perovskite thin films composited with polyethylene oxide (PEO) were fabricated by a solution processing method. Great enhancement of photoluminescence was observed and more attractively, two-photon-pumped random lasing action could be achieved at room temperature when pumped by a nanosecond pulse laser with excitation wavelength centered at 1064 nm. Evident transition from spontaneous upconversion emission to random lasing action was investigated by monitoring the log–log light emission slope and peak width at half height. The lasing threshold is at around 1.1 mJ cm⁻², which is comparable to that of other two-photon upconversion random lasers. The efficient random lasing emission originates from the multiple random scattering provided by the micrometer-scale rugged morphology and polycrystalline grain boundaries. Compared with conventional lasers that normally serve as a coherent light source, the perovskite random lasers show promise in fabricating low-cost thin-film lasing devices for flexible and speckle-free imaging applications.

Organic magneto-current of OLEDs reveals that ³ LE and ³ CT are participants in the “Scattering Channel” and the “Dissociation Channel” of triplet-charge annihilation, respectively.

Far-field plasmonic effect of Au nanoparticles was explored for high performance blue-light perovskite electroluminescent devices, achieving maximum luminance and external quantum efficiency as high as ~1110 cd m⁻² and 1.64%, respectively.