The photolithographic patterning of fine quantum dot (QD) films is of great significance for the construction of QD optoelectronic device arrays. However, the photolithography methods reported so far either introduce insulating photoresist or manipulate the surface ligands of QDs, each of which has negative effects on device performance. Here, we report a direct photolithography strategy without photoresist and without engineering the QD surface ligands. Through cross-linking of the surrounding semiconductor polymer, QDs are spatially confined to the network frame of the polymer to form high-quality patterns. More importantly, the wrapped polymer incidentally regulates the energy levels of the emitting layer, which is conducive to improving the hole injection capacity while weakening the electron injection level, to achieve balanced injection of carriers. The patterned QD light-emitting diodes (with a pixel size of 1.5 μm) achieve a high external quantum efficiency of 16.25% and a brightness of >1.4 × 105 cd/m2. This work paves the way for efficient high-resolution QD light-emitting devices.
Abstract Organic thin film transistor (OTFT) based nonvolatile memory has made significant progress due to its biocompatibility, flexibility, and low cost, in which ferroelectric transistor memory and floating gate transistor memory play the main roles in organic nonvolatile transistor memory. Here, a novel layered hybrid structure OTFT nonvolatile memory is invented by combining ferroelectric poly(vinylidene fluoride‐ co ‐trifluoroethylene) P(VDF‐TrFE) with a floating gate layer utilizing CdSe/ZnS quantum dots (QDs), which integrates the advantages of ferroelectric memory and floating gate memory. The core–shell structured CdSe/Zns QDs are acted as robust charge trapping centers due to their band structure similar to a quantum well, preventing the back diffuse of trapped charges, while P(VDF‐TrFE) provides additional polarized electric field to modulate the capture of charge. The resultant devices exhibit high on‐state current (≈10 −5 A), low off‐state current (≈10 −10 A), excellent switch ratio (≈10 5 ), and retention characteristic (>10 4 s). Furthermore, a superior memory window, more than 85.6% of scanning voltage range, higher than most reported organic transistor memories, is achieved, which endows the device wide operating condition and significant discrimination between on and off state. The fine‐structured OTFT memory opens up a unique path for desirable memory to meet the growing demand of microelectronic industry.
Optimizing the driving panel of display to decrease the number of driving lines is of importance to high-resolution displays. Especially, it is important to address the challenge of the increasing number of row and column electrode lines. In this work, an approach for realizing the one line-to-three LEDs driving method employing the noncarrier injection (NCI) operational mode has been demonstrated, and the NCI-LEDs using discrete components are constructed. The operating characteristics and principles of the NCI-LEDs are studied. It is demonstrated that electroluminescent (EL) output states of three parallel NCI-LEDs vary with driving frequency, that is, the NCI-LEDs has frequency-selective properties. Therefore, the separate control of three LEDs under the control of a single signal line is realized, and the subpixel circuit selection of three RGB colors is realized. This driving method can effectively mitigate the complexity of the electrode wiring required by the row–column scanning, which is expected to provide important guidance for the development of high-resolution displays.
Flexible White Organic Light-Emitting Diodes Based on Single-Walled Carbon Nanotube:Poly(3,4-ethylenedioxythiophene)/Poly(styrene sulfonate) Transparent Conducting Film, Beibei Zhang, Fushan Li, Zhixiao Lin, Chaoxing Wu, Tailiang Guo, Wenbin Liu, Yang Su, Jinhong Du
Solvent vapor annealing has been widely used in organic photovoltaics (OPV) to tune the morphology of bulk heterojunction active layer for the improvement of device performance. Unfortunately, the effect of solvent removal rate (SRR) after solvent annealing, which is one of the key factors that impact resultant morphology, on the morphology and device performance of OPV has never been reported. In this work, the nanoscale morphology of small molecule (SM):fullerene bulk heterojunction (BHJ) solar cell from different SRRs after solvent annealing was examined by small-angle neutron scattering and grazing incidence X-ray scattering. The results clearly demonstrate that the nanoscale morphology of SM:fullerene BHJ especially fullerene phase separation and concentration of fullerene in noncrystalline SM was significantly impacted by the SRR. The enhanced fullerene phase separation was found with a decrease of SRR, while the crystallinity and molecular packing of SM remained unchanged. Correlation to device performance shows that the balance between pure fullerene phase and mixing phase of SM and fullerene is crucial for the optimization of morphology and enhancement of device performance. Moreover, the specific interfacial area between pure fullerene phase and mixing phase is crucial for the electron transport and thus device performance. More importantly, this finding would provide a more careful and precise control of morphology of SM:fullerene BHJ and offers a guideline for further improvement of device performance with solvent annealing.
Abstract Achieving efficient white quantum dot light‐emitting diodes (WQLEDs) is highly desired because of their promising applications in general illumination and display backlight systems. Herein, a highly efficient WQLED with an extremely low input voltage is reported, which is fabricated via an all‐solution process by using an emitting layer with a mixture of red‐, blue‐, and green‐emitting quantum dots. When a facile strategy of light outcoupling with an optical lens is introduced, the device shows a maximum external quantum efficiency of 28.4%, which is the highest value reported so far. Moreover, the device exhibits a standard white emission with International Commission on Illumination (CIE) coordinates of (0.36, 0.34) at an extremely low input voltage of 3.2 V. This work provides a promising way for achieving high‐performance white quantum‐dot light‐emitting diodes with low driving voltage.
Abstract Perovskite quantum dots (PQDs) have emerged as promising candidates for next‐generation high‐quality lighting and high‐definition displays due to their outstanding luminescence properties, characterized by a narrow emission spectrum and tunable color. However, during the purification process involving polar solvents, ligand detachment from the quantum dot surface often induces crystal defects, thereby compromising their long‐term stability. Herein, the effects of various post‐processing strategies on PQD performance are systematically explored, including the use of oleic acid (OA), didodecyldimethylammonium bromide (DDAB), and their combinations, alongside OA‐assisted synthesis. Furthermore, a synergistic post‐processing strategy based on DDAB‐NaMeS (sodium methanesulfonate) is proposed to elucidate the mechanism of ligand reconstruction on the quantum dot surface during purification. The resulting PQDs demonstrated excellent stability over a storage period exceeding one month, and the corresponding Quantum Dots Light‐Emitting Diodes (QLEDs) achieved a peak external quantum efficiency (EQE) of 9.82%, representing a 1.91‐fold improvement over standard devices. These QLEDs exhibited exceptional optoelectronic performance, underscoring their potential for application in other sulfonic acid ligands and perovskite‐based materials.
Abstract Efficient in‐sensor computing necessitates linear, bidirectional, and centrosymmetric photoresponse weight updates; however, the realization of these attributes poses a persistent challenge, with most photosensor devices achieving linear analog weight updates while falling short of accomplishing bidirectional and centrosymmetric characteristics. Here, the development of a quantum dot (QD)–based bulk heterojunction synaptic transistor (QBST) with multi‐factor modulation through surface ligand engineering of blend QDs is reported. By controlling the charge transmission between QDs and the semiconductor, the QBST device enables tunable fading memory, which transforms linear weight updates in short‐chain devices into linear, bidirectional, and unprecedented centrosymmetric optical synaptic responses in long‐chain devices. Moreover, through the synergy of chemical and electric factors, the convolutional kernel of QBSTs‐based convolutional neural network realizes enhanced recognition for complex noisy fashion‐costume images, achieving an impressive 90.3% accuracy in the long‐chain device, highlighting the efficiency of centrosymmetric weight updates. The results demonstrate that surface ligand engineering offers a promising approach for customizable synaptic modulation, facilitating energy‐ and time‐efficient in‐sensor computing.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)