Photodetectors based on small-molecule organic semiconductor crystals

Small-molecule organic semiconductor crystals(SMOSCs) combine broadband light absorption(ultraviolet–visible–near infrared) with long exciton diffusion length and high charge carrier mobility. Therefore, they are promising candidates for realizing high-performance photodetectors. Here, after a brief resume of photodetector performance parameters and operation mechanisms, we review the recent advancements in application of SMOSCs as photodetectors, including photoconductors, phototransistors, and photodiodes. More importantly, the SMOSC-based photodetectors are further categorized according to their detection regions that cover a wide range from ultraviolet to near infrared. Finally, challenges and outlooks of SMOSC-based photodetectors are provided.

Few-layer fbrmamidinium lead bromide nanoplatelets for ultrapuregreen and high-efficiency light-emitting diodes

Formamidinium lead bromide perovskite(FAPbBr3)nanocrystals have attracted increasing attention due to their greener photoluminescence(PL)and higher thermal stability in comparison to more popular methylammonium lead bromide perovskite(MAPbBr3).Here we proposed a-facile and highly reproducible room-temperature method for the preparation of fewlayer(1-4)two-dimensional(2D)FAPbBr3 nanoplatelets(NPs)with ultrapure green PL at 532 nm and high photoluminescence quantum yield(PLQY)of 88%.High-efficiency ultrapure green light-emitting diodes(LEDs)based on the few-layer 2D FAPbBr3 NPs were further demonstrated.The LEDs showed a maximum current efficiency(CE)of 15.31cd/A and an external quantum efficiency(EQE)of 3.53%,which are significantly better than the FAPbBr3 polycrystalline film-based LEDs reported so far.Significantly,the 2D FAPbBr3 NPs-based LEDs exhibited an ultrapure-green color emission that could cover 97%of the Recommendation 2020(Rec.2020)color standard and 114%of the national television system committee(NTSC)standard in the CIE 1931 color space.Moreover,the devices possessed a much better stability than the MAPbBr3 nanocrystals-based LEDs in air;the half lifetime T50 of our devices was about 5 times Ion ger than that of MAPbBr3 nan ocrystals-based LEDs.This work demonstrates the great potential of FAPbBr3 NPs in light-emitting devices for future ultrahigh-resolution displays.

External-force-driven solution epitaxy of large-area 2D organic single crystals for high-performance field-effect transistors

Growth of two-dimensional(2D)organic single crystals(2DOSCs)on water surface has attracted increasing attention,because it can serve as a molecularly flat and defect-free substrate.However,large-area growth of 2DOSCs with controllable crystal orientation on water surface remains a key challenge.Herein,we develop a simple method,i.e.external-force-driven solution epitaxy(EFDSE),for the large-area growth of 2DOSCs at air/water interface.Using 2,7-didecylbenzothienobenzothiophene(C1o-BTBT)as an example,high-quality 2D C10-BTBT crystals on centimeter scale are generated by directionally controlling the spreading of organic solution on water surface with external force.Benefiting from the controllable crystal orientation with optimal charge transport,the corresponding 2DOSC-based organic field-effect transistors(OFETs)exhibit a high carrier mobility of 13.5 cm^2·V^-1·s^-1(effective mobility=5.4 cm^2·V^-1·s^-1 according to a reliability factor of 40%),which represents the best result achieved for water-surface-assembled 2DOSC based OFETs.Furthermore,by transterring the C1o-BTBT 2DOSCs to flexible substrates,devices with excellent bending stability are achieved.It is anticipated that our method will provide new insight into the controllable growth of large-area 2DOSCs for high-performance organic devices.