Researchers achieved ultrahigh efficiency of solution-processed simplified small-molecule OLEDs that use novel universal host materials.

Visible-blind ultraviolet (UV) photodetectors have received a great deal of attention for realizing Internet of Things technologies as well as for monitoring the level of UV exposure to humans. Realizing next-generation flexible and visible-blind UV photodetectors requires development of new functional material systems with easy fabrication, selectively strong UV light absorption, environmental friendliness, and high stability regardless of ambient conditions. Herein, flexible visible-blind UV photodetectors are successfully fabricated on the basis of two-dimensional ZnAl-layered double hydroxide (LDH) nanosheets with scroll structures grown on flexible substrates. The ZnAl-LDH nanosheet scrolls exhibit highly resistive semiconducting properties with a band gap of 3.2 eV and work function of 3.64 eV. The photodetector based on the ZnAl-LDH shows photoresponse in the UV spectral range below 420 nm, indicating visible-blind spectral response. In addition, the UV photodetector shows a maximum responsivity of 17 mA/W under illumination with 365 nm light. Moreover, the flexible photodetector shows reproducible photoresponse even after 1000 bending cycles, which indicates the acceptable stability of the ZnAl-LDH nanosheet scrolls.

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A series of small molecules that contained identical π-spacers (ethyne), a central diketopyrrolopyrrole (DPP) unit, and different aromatic electron-donating end-groups were synthesized and used in organic solar cells (OSCs) to study the effect of electron-donating groups on the device performance. The three compounds, DPP-A-Ph, DPP-A-Na, and DPP-A-An, possessed intense absorption bands that covered a wide range, from 350 to 750 nm, and relatively low HOMO energy levels, from -5.50 to -5.55 eV. DPP-A-An, which contained anthracene end-groups, demonstrated a stronger absorbance and a higher hole mobility than DPP-A-Ph, which contained phenyl groups, and DPP-A-Na, which contained naphthalene units. The power-conversion efficiencies (PCEs) of OSCs based on organic:PC71BM blends (1:1, w/w) with a processed DIO additive were 3.93% for DPP-A-An, 3.02% for DPP-Na, and 2.26% for DPP-A-Ph. These findings suggest that a DPP core that is functionalized with electron-donating capping groups constitutes a promising new class of solution-processable small molecules for OSC applications.

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