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 (C10-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 cm²·V^-1·s^-1 (effective mobility ≈ 5.4 cm²·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 transferring the C₁₀-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.

Silicon nanowire (SiNW) fabrics are of great interest for fabricating high-performance multifunctional wearable sensors. However, it remains a big challenge to fabricate high-quality SiNW fabrics in a simple and efficient manner. Here we report, for the first time, one-step growth of large-area SiNW fabrics for multifunctional wearable sensors, by using a massive metal-assisted chemical vapor deposition (CVD) method. With bulk Sn as a catalyst source, numerous millimeter-long SiNWs grow and naturally interweave with each other, forming SiNW fabrics over 80 cm² in one experiment. In addition to intrinsic electronic properties of Si materials, the SiNW fabrics also feature high flexibility, good tailorability and light weight, rendering them ideal for fabricating multifunctional wearable sensors. The prototype sensors based on the SiNW fabrics could effectively detect various stimuli including temperature, light, strain and pressure, with outstanding performance among reported multifunctional sensors. We further demonstrate the integration of the prototype sensors onto the body of a robot, enabling its perception to various environmental stimuli. The ability to prepare high-quality SiNW fabrics in a simple and efficient manner will stimulate the development of wearable devices for applications in portable electronics, Internet of Things, health care and robotics.

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 few-layer (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 15.31 cd/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 longer than that of MAPbBr₃ nanocrystals-based LEDs. This work demonstrates the great potential of FAPbBr₃ NPs in light-emitting devices for future ultrahigh-resolution displays.