A novel small-molecule acceptor, (2,2'-((5E,5'E)-5,5'-((5,5'-(4,4,9,9-tetrakis(5-hexylthiophen-2-yl)-4,9-dihydro-s-indaceno[1,2-b:5,6-b']dithiophene-2,7-diyl)bis(4-(2-ethylhexyl)thiophene-5,2-diyl))bis(methanylylidene)) bis(3-hexyl-4-oxothiazolidine-5,2-diylidene))dimalononitrile (ITCN), end-capped with electron-deficient 2-(3-hexyl-4-oxothiazolidin-2-ylidene)malononitrile groups, is designed, synthesized, and used as the third component in fullerene-free ternary polymer solar cells (PSCs). The cascaded energy-level structure enabled by the newly designed acceptor is beneficial to the carrier transport and separation. Meanwhile, the three materials show a complementary absorption in the visible region, resulting in efficient light harvesting. Hence, the PBDB-T:ITCN:IT-M ternary PSCs possess a high short-circuit current density (J ) under an optimal weight ratio of donors and acceptors. Moreover, the open-circuit voltage (V ) of the ternary PSCs is enhanced with an increase of the third acceptor ITCN content, which is attributed to the higher lowest unoccupied molecular orbital energy level of ITCN than that of IT-M, thus exhibits a higher V in PBDB-T:ITCN binary system. Ultimately, the ternary PSCs achieve a power conversion efficiency of 12.16%, which is higher than the PBDB-T:ITM-based PSCs (10.89%) and PBDB-T:ITCN-based ones (2.21%). This work provides an effective strategy to improve the photovoltaic performance of PSCs.

Water radical cations, the crucial intermediates in many aqueous reactions and biochemical processes, are difficult to be experimentally investigated due to its short lifetime and low abundance. Herein, a homemade device based on energy-tunable discharge was employed to deposit suitable amounts of energy to atmospheric pressure pure water vapor for abundant production of water radical cations, which were stabilized as (H 2 O) n +• (n=2-5) with the maximal abundance (≥ 8.3×10 6 cps) for (H 2 O) 2 +• as characterized by mass spectrometry (MS).The abundance of water radical cations was optimized by adjusting the experimental parameters such as discharge voltage (2.5 kV), temperature of the MS inlet (140 o C), carrier gas flow (20 mL/min) and the distance between the discharge tip and the MS inlet (12 mm). The ambient formation of water radical cations was further confirmed by the high reactivity of the as-prepared water radical cations, which instantly reacted with benzene, ethyl acetate and dimethyl disulfide, showing rich chemistry with the ionic and radical characters. Moreover, the computations confirm that the O-O single-electron bound dimer (B) as well as the hydronium hydroxyl radical complex (A) accounts for the unusual chemistry of the water radical cations, providing a facile approach to access the high reactivity of water radical cations under the ambient condition.

Two blue fluorophores with excellent hybridized local and charge-transfer (HLCT) and "hot exciton" properties were developed as the blue emitter and the host for orange-red phosphor to achieve highly efficient fluorescent/phosphorescent (F/P) hybrid white organic light-emitting diodes (WOLEDs) in a single-emissive-layer single-dopant (SEML-SD) architecture even at a high concentration of phosphorescent dopant. In the devices, part of the triplet excitons of the blue fluorophores can be utilized to realize reverse intersystem crossing from the triplet excited states to the singlet excited states for blue emission, and the diffusion volume range of the triplet excitons is reduced significantly. When the phosphorescent dopant concentration is up to 1.0 wt %, which is ten times higher than the traditional single-EML-SD F/P hybrid WOLEDs, highly efficient white emission was still achieved with maximum total external quantum efficiency (EQE) of 23.8%, current efficiency (CE) of 56.1 cd A(-1), and power efficiency (PE) of 62.9 lm W(1-). The results will supply a novel method for obtaining high efficiency F/P hybrid WOLEDs in a SEML-SD architecture with easily controllable doping concentration.