Organic Electronics最新文献

Organic thin-film transistor (OTFT) has been adopted as a promising sensing platform to detect DNA target molecules by analyzing their electrical parameters. The source/drain current ratio of OTFT (with and without DNA molecules) as the sensor sensitivity have been widely utilized to detect and identify DNA molecules. In this paper, pentacene as a typical organic semiconductor with various thin-film thicknesses have been adopted as the active layer of OTFT that induce to the changeable sensor sensitivity for the DNA molecules. Importantly, the sensitivity of the device shows the remarkable dependence in the applied gate voltages (V_G) and an improved trend is observed with the lowering of V_G. Importantly, a ten-fold improvement in the sensor sensitivity is achieved by the optimization of channel thicknesses at the low V_G condition. Furthermore, the variable-temperature measurements are carried out to explore the charge mechanism of OTFT induced by the DNA molecules. Our studies indicate the sensor sensitivity is mainly determined by the charge-injection process of OTFT arisen in the linear region. Current work will be helpful for deeply understanding the operating mechanism of OTFT-based biosensors.

Robust encapsulation is indispensable for flexible organic solar cells (OSCs) moving into practical applications because the materials and interfaces of the cells are susceptible to water vapor and oxygen under illumination. Fleixble barrier films are one of the key parts of the encapsulation. In this work, we report the fabrication of flexible barrier films comprising of alternating parylene C and alumina dyads, and the application of these barrier films to encapsulate flexible OSCs. Parylene C layers are deposited by chemical vapor deposition (CVD) and dense alumina layers are grown by atomic layer deposition (ALD). The fabricated film comprising of three dyads of parylene C and alumina shows a low water vapor transmission rate (WVTR) of 8.7 × 10⁻⁴ g m⁻² day⁻¹ (25 °C, 100% RH) devrived by calcium conductance test. Encapsulated OSCs could retain 80% of their initial efficiency after immersed into water for 624 h, and could retain 81% of their initial efficiency under continuous illumination for 1156 h in ambient atmosphere.

This study explores the physical properties and electrical characteristics of a regioregular poly 3-hexylthiophene (rr-P3HT) semiconductor blended with the polymer insulator polystyrene. Given the high operating voltage required by conventional P3HT transistors, we employed a hybrid dielectric layer, combining plasma-reacted metal oxide with a polymer pre-layer (AlO_x/PMMA and HfO_x/PMMA), to reduce the operating voltage of P3HT transistors. As a result, an operating voltage lower than −5 V for the blended sample was achieved. The structural, morphological, and electrical properties of the prepared blended sample were investigated using XRD, AFM, XPS, UV–Visible spectroscopy, Raman spectroscopy, and I–V characteristics. The blended sample exhibits improved crystalline ordering and an extended effective conjugation length, accompanied by an increased formation of dendritic P3HT fibrils that enhance UV absorption. PS captures generated electrons, effectively delaying their recombination with generated holes in P3HT. This leads to heightened UV responsivity in P3HT/PS transistors. The key discovery of this study is the ultra-low power consumption UV sensing device. The blended sample, illuminated with a UV intensity of 550 μW/cm², exhibited the highest sensitivity of 194.5, nearly 60 times higher than that of pristine P3HT. Consequently, our investigated device shows promise for applications in visible-blind sunlight or environmental monitoring systems, given its ultra-high-power efficiency.

In this work, we designed and synthesized two new hole-transporting materials with a nonplanar three-dimensional (3D) conformation. They were achieved by incorporating spiro[fluorene-9,9′-xanthene] as a cross-shaped configuration scaffold and adding either mono- (H1) or bis- benzodioxino[2,3-b]pyrazine (H2) pyrazine as pendant groups. Both compounds exhibit remarkable thermal stability, with thermal decomposition temperature (T_d) of 462 (H1) and 504 °C (H2), respectively. Moreover, the structural substitution with benzodioxino[2,3-b]pyrazine units successfully aligned the energy levels of both materials with the perovskite quantum dot luminescence layer. Hereby, the fabricated perovskite QLEDs using H1 as hole-transporting materials (HTMs) featured an excellent average external quantum efficiency (EQE) of up to 9.5% with a maximum luminance of 22368 cd m⁻², which is much higher than that of the H2-based devices with an EQE of 6.6% under the same conditions. The excellent device performance from H1 can be attributed to its asymmetric structure by the introduction of monosubstituted benzodioxino[2,3-b]pyrazine groups, as evidenced by its high hole mobility of 1.90 × 10⁻⁴ cm² V⁻¹ s⁻¹ and improved interface interaction with adjunct layers. Thus, this design approach may bring a fresh perspective to the utilization of solution-processable small-molecule HTMs in high-performance Pe-QLEDs and other optoelectronics in the future.

The demand for next-generation organic field-effect transistors (OFETs) with low operating voltage is becoming gradually attractive in many application areas, such as flexible/wearable medical sensors and stretchable electronics. While using high dielectric materials is a potent approach, it often results in a decline in field-effect mobility or on/off ratio. Unfortunately, achieving low-voltage operation has hindered practical applications, compromising device performance. Here, we discovered for the first time a novel class of low-driving voltage pentacene transistors adopting gate insulators composed of nitrogen-plasma-reacted AlN_x, TiN_x, and TaN_x. This exciting discovery is simple, affordable, environmentally friendly, and secure. X-ray photoelectron spectrometer (XPS) analysis reveals that the as-formed metal nitrides are composited with certain native oxide components, exhibiting outstanding leakage current blocking capacity and a high dielectric constant. Further, the surface energy of metal nitrides was altered by applying a thin layer of poly-(4-vinylphenol) (PVP). This modification improved the growth of pentacene grains and the insulator/pentacene interface. The best devices by comprehensive evaluation, the TiN_x samples, achieve a high average of field-effect mobility ∼1.41 cm²/Vs, a subthreshold swing of 0.19 V/dec, an on/off current ratio of ∼10⁴, and a turn-on voltage close to 0 V, which shows promising potential candidates for the flexible electronic devices, optoelectronic devices, and neuromorphic application.

Interface exciplex organic light-emitting diodes (OLEDs) have attracted intense attention due to the advantages including well-confined recombination regions, barrier-free charge transport and thermally activated delayed fluorescence (TADF) characteristics. To investigate the spin evolutions and dynamics of electron-hole (e-h) pairs, such as polaron pairs (PPs) and charge transfer (CT) excitons, in interface exciplex OLEDs is crucial for a better understanding on their energy gain and loss mechanisms. In this work, microscopic dynamics of e-h pairs in interface exciplex OLEDs were investigated by magneto-electroluminescence (MEL) and magneto-conductivity (MC) responses. The interface exciplex OLEDs were fabricated using 4,4,4-tris(N-3-methylphenyl-N-phenylamino) triphenylamine (m-MTDATA) as the donor and 2,4,6-tris(biphenyl-3-yl)-1,3,5-triazine (T2T) as the acceptor. Hyperfine interaction (HFI)- and different g-factors between electrons and holes (Δg mechanism)-dominated spin flip processes, and recombination and dissociation processes such as triplet-triplet annihilation (TTA) and triplet-charge annihilation (TQA) were identified, and their changes with temperature and current were explored. Our results may provide valuable insights into the evolution of carriers and facilitate the development of interface exciplex-based OLEDs.

The high energy loss (E_loss) in organic solar cells (OSCs) is being the one of major problem, which limit the power conversion efficiency (PCE) of OSCs. In this work, we designed and synthesized three perylene diimide (PDI)-based Acceptor’-Donor-Acceptor-Donor- Acceptor’ (A′-DAD-A′) small molecules namely anti-PDFC-Cx (C8, C10, and C12) by changing the length of linear chains on IDT cores to investigate how the length of linear side chain affects E_loss and the power conversion efficiencies (PCEs) of OSCs. The optical energy bandgap and stacking mode for three anti-PDFC-Cx (C8, C10, and C12) remain the same, which were not influenced by the different lengths of side chains. Increasing the length of side chains on IDT cores from C8 to C10 and C12 would improve the PCE of PM6: anti-PDFC-Cx based devices from 11.52% to 12.43% and 12.27%, particularly the V_oc increasing from 0.98 V of anti-PDFC-C8 and 1.00 V of anti-PDFC-C10 to 1.02 V of anti-PDFC-C12. E_loss analysis indicated the value of E_loss reduced as the length increases from C8, to C12. These results demonstate linear side chain engineer is an effective method to reduce E_loss and realize high PCE on the bases of not modulating the stacking mode of acceptor.

The perceived diminished sensitivity of Polymer Light-Emitting Electrochemical Cells (LECs) to electrode material and active layer thickness compared to Organic Light-Emitting Diodes (OLEDs) due to electrochemical doping, positions them as a focal point in emerging electronic applications. However, empirical evidence reveals the electrode still influences device performance. Simultaneously, electrochemical doping involves side reactions at the cathode, predominantly with oxygen. Nevertheless, the impact of oxygen reduction reaction on the device performance concerning electrode effects remains underexplored. This study centers on the pivotal influence of oxygen reduction reaction on the electrode effect in LECs. The investigation of the doping process for various electrodes and active layer thicknesses was conducted using photoluminescence imaging. Through controlling temperatures and vacuum levels, obtained time-current curves undergo fitting procedures, which enables quantitative analysis of oxygen reduction reaction effects on both electrode and film thickness. The results underscore the impact of oxygen reduction reaction on the performance of the device induced by electrodes, emphasizing the pronounced effect on the activation energy of the reduction reaction dictated by both the electrode work function and oxygen concentration. In addition, this study elucidates that the utilization of a low-work-function bottom contact in conjunction with a thicker active layer exerts a discernible influence on the device's current magnitude.

—On-site analysis of multiple analytes from different classes (such as heavy metals, proteins and small molecules), at the sensitivity required for a selected application, is a hard technological challenge. In this context, optical sensing in miniaturized systems has the largest potential. We present here the design and optimization of a miniaturized optical sensor with multiple channels, capable of multimodal optical detection in each channel, and the proof-of-concept realization of sub-systems providing two complementary detection modes: plasmon enhanced fluorescence and localized surface plasmon resonance. The multichannel (enabling multiplexing) and multimodal optical sensor is designed to have a total size of one inch-square and optimized sensing performance, obtained by combining organic optoelectronic and nanoplasmonic components.

The presence of defects in the perovskite absorption layer significantly reduces the photovoltaic performance of perovskite solar cells (PSCs). In this study, a Lewis base Triethanolamine (TEA) is introduced on the perovskite surface, and the hydrogen bond formed by its hydroxyl group with Pb ions or I ions fix the halogen anion of perovskite and suppresses the migration of ions in perovskite. TEA has an obvious effect at the grain boundary, significantly improving the surface quality of the perovskite film and the device's efficiency. Compared with the pristine device (19.26%), the device after passivation at the optimal concentration exhibits better photovoltaic performance and stability, which obtained the champion efficiency of 20.39% and remained at 88.3% of the initial efficiency after being aged 1080 h without encapsulation. We expect that adding TEA to the perovskite surface will provide a useful strategy to enhance the performance of PSCs, as well as air and thermal stability.