Organic molecules with dual triplet-harvesting channels enable efficient X-ray scintillation and imaging

Organic scintillators have recently gained considerable attentions in X-ray detection for their potential applications in biomedical radiograph and security inspection.However,the weak X-ray absorption and/or inefficient exciton utilization have limited the development and commercialization of organic scintillators.Currently,high-performance X-ray organic scintillators are scarce and organic scintillators with dual triplet-harvesting channels have not been explored before.Here,we develop several proof-of-concept sulfone-based organic molecules,C1–C7,using different alkoxy chains to manipulate molecular packing mode.These materials exhibit dual triplet-harvesting channels of thermally activated delayedfluorescence(TADF)and room-temperature phosphorescence(RTP)in aggregated state.Inspiringly,these molecules display distinct radioluminescence under the X-ray stimulation.Among them,C6 behaves the highest light yield of 16,558 photons MeV-1.Moreover,clear X-ray images are demonstrated in both aggregated state and single-molecule level.High spatial resolutions of 15.0 and 10.6 line pairs per millimeter(lp mm-1)are achieved for rigid andflexible scintillator screens,exceeding most reported organic and conventional inorganic scintillators.These results highlight the great potential of organic molecules with TADF and RTP nature for efficient X-ray scintillation and imaging.

Tuning of Förster Resonance Energy Transfer in Metal–Organic Frameworks: Toward Amplified Fluorescence Sensing

The assembly of Förster resonance energy transfer(FRET)donor and acceptor for amplified fluorescence sensing has been considered a big challenge.Herein,by using the multivariate approach,we report the design and synthesis of a series of FRET-based metal–organic frameworks(MOFs)with variable donor fluorophore-to-the-acceptor ratios.

Triplet manipulation for strong luminescence

The excitons in organic semiconductors undergo either radiative or non-radiative decay after excitation.Unlike the singlets in the fluorescence counterparts,the triplets in the heavy-metal based phosphorescent emitter,thermally activated delayed fluorescence emitter with a small singlet-triplet gap,and metal-free room-temperature phosphorescence emitter with strong spinorbital coupling,respectively,could be feasibly harvested for photon generation, which are responsible for the theoretical 100% internal quantum efficiency.

Luminescent gold(Ⅲ)exciplexes enable efficient multicolor electroluminescence

The control of excited states and related emissive properties of gold(Ⅲ)complexes mainly depends on the modulation of intramolecular electronic interactions among gold(Ⅲ)metal center,chelating ligands and/or peripheral groups.However,luminescent gold(Ⅲ)systems based on intermolecular electronic interactions have never been explored.Here we report a series of proof-of-concept gold(Ⅲ)exciplexes using a simple gold(Ⅲ)complex,AuDPPy,as an electron acceptor.The emissive properties of gold(Ⅲ)exciplexes can be regulated by combining AuDPPy with different donors.Inspiringly,these gold(Ⅲ)exciplexes have donor-dependent emission mechanisms:dominant phosphorescence or dual radiative channels of thermally activated delayed fluorescence(TADF)and phosphorescence.Consequently,these gold(Ⅲ)exciplexes deliver green-to-red electroluminescence with external quantum efficiencies(EQEs)of up to 10.1%.More importantly,using these gold(Ⅲ)exciplexes to host multi-resonance TADF emitters results in narrowband yellow,orange,and deep-red electroluminescence with high EQEs of 23.5%,24.4%,and 27.4%,respectively,competitive to the highest values for gold(Ⅲ)OLEDs in similar color gamut.

Alloy-like ternary polymer solar cells with over 17.2% efficiency

Ternary strategy has been considered as an efficient method to achieve high performance polymer solar cells(PSCs). A power conversion efficiency(PCE) of 17.22% is achieved in the optimized ternary PSCs with10 wt% MF1 in acceptors. The over 8% PCE improvement by employing ternary strategy is attributed to the simultaneously increased JSCof 25.68 mA cm^-2, VOCof 0.853 V and FF of 78.61% compared with Y6 based binary PSCs. The good compatibility of MF1 and Y6 can be confirmed from Raman mapping, contact angle,cyclic voltammetry and morphology, which is the prerequisite to form alloy-like state. Electron mobility in ternary active layers strongly depends on MF1 content in acceptors due to the different lowest unoccupied molecular orbital(LUMO) levels of Y6 and MF1, which can well explain the wave-like varied FF of ternary PSCs. The third-party certified PCE of 16.8% should be one of the highest values for single bulk heterojunction PSCs. This work provides sufficient references for selecting materials to achieve efficient ternary PSCs.

DDTC-Na-based colorimetric chemosensor for the sensing of cyanide in water

Sodium diethyldithiocarbamate (DDTC-Na) was demonstrated to be a new colorimetric cyanide chemosensor by utilizing an indirect trick. First, some copper ions were added to the colorless aque- ous solution of DDTC-Na. Then, the resultant brown solution was studied upon the addition of different anions, including Cl-, I-, IO3-, SO42-, NO-2, Br-, H2PO4-, F-, SCN-, HSO-4, ClO-4 and CN-. It was observed by naked eyes that the brown solution changed to colorless immediately after the addition of the trace cyanide, but there were no changes towards other anions, making DDTC-Na a good selective cyanide chemosensor in pure water.