Organic field‐effect transistors and near‐infrared (NIR) organic phototransistors (OPTs) have attracted world's attention in many fields in the past decades. In general, the sensitivity, ...distinguishing the signal from noise, is the key parameter to evaluate the performance of NIR OPTs, which is decided by responsivity and dark current. 2D single crystal films of organic semiconductors (2DCOS) are promising functional materials due to their long‐range order in spite of only few molecular layers. Herein, for the first time, air‐stable 2DCOS of n‐type organic semiconductors (a furan‐thiophene quinoidal compound, TFT‐CN) with strong absorbance around 830 nm, by the facile drop‐casting method on the surface of water are successfully prepared. Almost millimeter‐sized TFT‐CN 2DCOS are obtained and their thickness is below 5 nm. A competitive field‐effect electron mobility (1.36 cm2 V−1 s−1) and high on/off ratio (up to 108) are obtained in air. Impressively, the ultrasensitive NIR phototransistors operating at the off‐state exhibit a very low dark current of ≈0.3 pA and an ultrahigh detectivity (D*) exceeding 6 × 1014 Jones because the devices can operate in full depletion at the off‐state, superior to the majority of the reported organic‐based NIR phototransistors.
High‐performance organic field‐effect transistors and near‐infrared phototransistors with n‐type two‐dimensional organic single crystals are successfully fabricated. A field‐effect electron mobility (1.36 cm2 V−1 s−1) and high on/off ratio (108) are obtained. Impressively, the ultrasensitive near‐infrared phototransistors exhibit an ultrahigh detectivity exceeding 6 × 1014 Jones, superior to the majority of the reported organic‐based near‐infrared phototransistors.
The power conversion efficiencies (PCEs) of small molecule acceptor (SMA)‐based organic solar cells have already exceeded 18%. However, the development of polymer acceptors still lags far behind ...their SMA counterparts mainly due to the lack of efficient polymer acceptors. Herein, a series of polymer acceptors named PY‐X (with X being the branched alkyl chain) are designed and synthesized by employing the same central core with the SMA L8‐BO but with different branched alkyl chains on the pyrrole motif. It is found that the molecular packing of SMA‐HD featuring 2‐hexyldecyl side chain used in the synthesis of PY‐HD is similar to L8‐BO, in which the branched alkyl chains lead to condensed and high‐order molecular assembly in SMA‐HD molecules. When combined with PM6, PY‐HD‐based all polymer solar cell (all‐PSC) exhibits a high PCE of 16.41%, representing the highest efficiency for the binary all‐PSCs. Moreover, the side‐chain modification on the pyrrole site position further improves the performance of the all‐PSCs, and the PY‐DT‐based device delivers a new record high efficiency of 16.76% (certified as 16.3%). The work provides new insights for understanding the structure–property relationship of polymer acceptors and paves a feasible avenue to develop efficient conjugated polymer acceptors.
A series of polymer acceptors named PY‐X have been synthesized. By optimizing the length of branched alkyl chains, PY‐HD (2‐hexyldecyl substitution)‐based all polymer solar cell (all‐PSC) delivers a high efficiency of 16.76%, with an open‐circuit voltage of 0.949 V, and an extremely low non‐radiative voltage loss of 0.18 V, representing the highest efficiency for binary all‐PSCs.
Solution-processed metal-halide perovskites are emerging as one of the most promising materials for displays, lighting and energy generation. Currently, the best-performing perovskite optoelectronic ...devices are based on lead halides and the lead toxicity severely restricts their practical applications. Moreover, efficient white electroluminescence from broadband-emission metal halides remains a challenge. Here we demonstrate efficient and bright lead-free LEDs based on cesium copper halides enabled by introducing an organic additive (Tween, polyethylene glycol sorbitan monooleate) into the precursor solutions. We find the additive can reduce the trap states, enhancing the photoluminescence quantum efficiency of the metal halide films, and increase the surface potential, facilitating the hole injection and transport in the LEDs. Consequently, we achieve warm-white LEDs reaching an external quantum efficiency of 3.1% and a luminance of 1570 cd m
at a low voltage of 5.4 V, showing great promise of lead-free metal halides for solution-processed white LED applications.
The sensitivity of conventional thin‐film OFET‐based sensors is limited by the diffusion of analytes through bulk films and remains the central challenge in sensing technology. Now, for the first ...time, an ultrasensitive (sub‐ppb level) sensor is reported that exploits n‐type monolayer molecular crystals (MMCs) with porous two‐dimensional structures. Thanks to monolayer crystal structure of NDI3HU‐DTYM2 (NDI) and controlled formation of porous structure, a world‐record detection limit of NH3 (0.1 ppb) was achieved. Moreover, the MMC‐OFETs also enabled direct detection of solid analytes of biological amine derivatives, such as dopamine at an extremely low concentration of 500 ppb. The remarkably improved sensing performances of MMC‐OFETs opens up the possibility of engineering OFETs for ultrasensitive (bio)chemical sensing.
MMCs make sense: Two‐dimensional porous and nonporous monolayer molecular crystals (MMCs) of NDI3HU‐DTYM2 (NDI) were controllably synthesized by drop‐casting on different substrates. Both MMC sensors based on organic field‐effect transistors show high‐sensitivity performance to NH3 vapor. The porous MMC showed relative sensitivity of 72 % upon exposure to 0.1 ppb NH3, while the fluorescent intensity decreased by 40.9 % when exposed to 10 ppb NH3.
Self-assembly of monolayers of functional molecules on dielectric surfaces is a promising approach for the development of molecular devices proposed in the 1970s. Substrate chemically bonded ...self-assembled monolayers of semiconducting conjugated molecules exhibit low mobility. And self-assembled monolayer molecular crystals are difficult to scale up and limited to growth on substrates terminated by hydroxyl groups, which makes it difficult to realize sophisticated device functions, particularly for those relying on n-type electron transport, as electrons suffer severe charge trapping on hydroxyl terminated surfaces. Here we report a gravity-assisted, two-dimensional spatial confinement method for bottom-up growth of high-quality n-type single-crystalline monolayers over large, centimeter-sized areas. We demonstrate that by this method, n-type monolayer molecular crystals with high field-effect mobility of 1.24 cm
V
s
and band-like transport characteristics can be grown on hydroxyl-free polymer surface. Furthermore, we used these monolayer molecular crystals to realize high-performance crystalline, gate-/light-tunable lateral organic p-n diodes.
Optoelectronic devices based on metal halide perovskites, including solar cells and light‐emitting diodes, have attracted tremendous research attention globally in the last decade. Due to their ...potential to achieve high carrier mobilities, organic–inorganic hybrid perovskite materials can enable high‐performance, solution‐processed field‐effect transistors (FETs) for next‐generation, low‐cost, flexible electronic circuits and displays. However, the performance of perovskite FETs is hampered predominantly by device instabilities, whose origin remains poorly understood. Here, perovskite single‐crystal FETs based on methylammonium lead bromide are studied and device instabilities due to electrochemical reactions at the interface between the perovskite and gold source–drain top contacts are investigated. Despite forming the contacts by a gentle, soft lamination method, evidence is found that even at such “ideal” interfaces, a defective, intermixed layer is formed at the interface upon biasing of the device. Using a bottom‐contact, bottom‐gate architecture, it is shown that it is possible to minimize such a reaction through a chemical modification of the electrodes, and this enables fabrication of perovskite single‐crystal FETs with high mobility of up to ≈15 cm2 V−1 s−1 at 80 K. This work addresses one of the key challenges toward the realization of high‐performance solution‐processed perovskite FETs.
Electrochemical reaction at the interface between the perovskite and a nominally inert gold metal electrode during device operation is investigated in perovskite single‐crystal field‐effect transistors (FETs). Such interfacial reactions can be minimized through suitable chemical modification of electrodes, allowing the demonstration of single‐crystal perovskite FETs with mobilities of up to ≈15 cm2 V−1 s−1 at low temperature.
To improve the detection ability of infrared small targets in complex backgrounds, an improved detection algorithm YOLO-SASE is proposed in this paper. The algorithm is based on the YOLO detection ...framework and SRGAN network, taking super-resolution reconstructed images as input, combined with the SASE module, SPP module, and multi-level receptive field structure while adjusting the number of detection output layers through exploring feature weight to improve feature utilization efficiency. Compared with the original model, the accuracy and recall rate of the algorithm proposed in this paper were improved by 2% and 3%, respectively, in the experiment, and the stability of the results was significantly improved in the training process.
The integration of high charge carrier mobility and high luminescence in an organic semiconductor is challenging. However, there is need of such materials for organic light-emitting transistors and ...organic electrically pumped lasers. Here we show a novel organic semiconductor, 2,6-diphenylanthracene (DPA), which exhibits not only high emission with single crystal absolute florescence quantum yield of 41.2% but also high charge carrier mobility with single crystal mobility of 34 cm(2) V(-1) s(-1). Organic light-emitting diodes (OLEDs) based on DPA give pure blue emission with brightness up to 6,627 cd m(-2) and turn-on voltage of 2.8 V. 2,6-Diphenylanthracene OLED arrays are successfully driven by DPA field-effect transistor arrays, demonstrating that DPA is a high mobility emissive organic semiconductor with potential in organic optoelectronics.
A kind of sulfonated graphene (around 3 nm thick) with high dispersion properties has been synthesized. It is demonstrated to adsorb persistent organic aromatic pollutants effectively from aqueous ...solutions. The adsorption capability of the prepared sulfonated graphene nanomaterials approaches ∼2.3–2.4 mmol g−1 for naphthalene and 1‐naphthol, which is one of the highest capabilities of today's nanomaterials. This highly effective adsorbent may be a promising candidate to remove aromatic chemicals from large volumes of aqueous solutions. It opens a new door for cost effective environmental pollution management with graphene in the near future.
A new fluorinated electron acceptor (FINIC) based on 6,6,12,12‐tetrakis(3‐fluoro‐4‐hexylphenyl)‐indacenobis(dithieno3,2‐b;2′,3′‐dthiophene) as the electron‐donating central core and ...5,6‐difluoro‐3‐(1,1‐dicyanomethylene)‐1‐indanone as the electron‐deficient end groups is rationally designed and synthesized. FINIC shows similar absorption profile in dilute solution to the nonfluorinated analogue INIC. However, compared with INIC, FINIC film shows red‐shifted absorption, down‐shifted frontier molecular orbital energy levels, enhanced crystallinity, and more ordered molecular packing. Single‐crystal structure data show that FINIC molecules pack into closer 3D “network” motif through H‐bonding and π–π interaction, while INIC molecules pack into incompact “honeycomb” motif through only π–π stacking. Theoretical calculations reveal that FINIC has stronger electronic coupling and more molecular interactions than INIC. FINIC has higher electron mobilities in both horizontal and vertical directions than INIC. Moreover, FINIC and INIC support efficient 3D exciton transport. PBD‐SF/FINIC blend has a larger driving force for exciton splitting, more efficient charge transfer and photoinduced charge generation. Finally, the organic solar cells based on PBD‐SF/FINIC blend yield power conversion efficiency of 14.0%, far exceeding that of the PBD‐SF/INIC‐based devices (5.1%).
A fused‐ring electron acceptor, FINIC, with fluorination of both end groups and side chains is designed and synthesized, and compared with its nonfluorinated analogue, INIC. FINIC exhibits 3D molecular stacking, exciton transport and charge transport. FINIC‐based organic solar cells yield an efficiency of 14.0%, far exceeding that of the INIC‐based devices (5.1%).
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