Search

A new conjugated-block copolymer PBDB-YTCl-2 was synthesized. The photovoltaic performance, morphological characteristics and physical mechanisms of PBDB-YTCl-2 were compared with those of the bulk-heterojunction PBDB-T:PYCl-2 system.

Summary The field of all-polymer solar cells (all-PSCs) has experienced rapid development during the past few years, mainly driven by the design of efficient polymer acceptors (PAs). However, the polymer/polymer blend systems still lag far behind polymer/small molecule acceptor counterparts in power conversion efficiencies (PCEs). Here, we designed a near-infrared PA PY2F-T and paired it with polymer donor PM6 to fabricate all-PSCs with 15.0% PCE. Afterwards, PYT as the third component was introduced into the PM6:PY2F-T host system. Because of the complementary absorption bands and finely tuned microstructures of the ternary blend, the PCE is improved up to 17.2%, with the external quantum efficiency over 80% in visible and near-infrared spectral regions. Impressively, the ternary blend exhibited less energy loss, better light-soaking and photo-thermal stabilities than did the corresponding binary systems. This work promotes the development of high-performance ternary all-polymer systems and heralds a brighter future for accelerating the possible applications of all-PSCs.

High-resolution passive-matrix polymer light-emitting displays with printed cathodes are achieved by combining delicate cathode deposition and multifunctional buffer layer fabrication. Unlike other printing methods and printed materials, ink-jetting conducting nano-particles as cathode can provide high-resolution cathode patterns and excellent continuity along the fine cathode lines without any mechanical pressure on the organic layers. The buffer layer between the printed cathode and the organic active layers, was fabricated by mixing the water/alcohol-soluble polymer poly[9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene-alt-2,7-(9,9-dioctylfluorene)] (PFNR2) and a curable epoxy adhesive. It offers the functions of solvent-proof, electron-injection, and proper affinity with the cathode ink. While improving the performance of devices, especially blocking the leakage current greatly, the cross-linked buffer layer also induces a novel phenomenon of ‘linear η-J plot’, which can be derived to interesting and realistic results. Red, green, and blue monochrome and full-color polymer light-emitting displays with a content format of 96 × 3 × 64 show neither dead pixels nor dead lines. Under optimized steps of curing, the nano silver ink forms continuous, defect-free, and low-resistance cathode rows without any distortion. The red, green, and blue displays exhibit the current efficiencies of 0.62, 4.38 and 0.93 cd/A, and CIE color coordinates of (0.63, 0.37), (0.39, 0.57) and (0.18, 0.16), respectively. The cathode printing technique removes the need of high vacuum for thermal evaporation of the cathode metal, which could lead to the industrial roll-to-roll process to manufacture the flat panel displays.

The performance of the single organic submicrometer ribbon based photodetector has been improved by one order of magnitude by combining a better crystalline structure with proper surface engineering, such as coating a dielectric layer PMMA or PS between the substrate and the organic semiconductor. The photoconductivity gain is as much as 1.3 × 10 4 , the responsivity is about 4372 A W −1 at the field of about 2 × 10 6 V m −1 , and the highest on/off ratio reaches 10 4 . The extremely high gain is attributed to the high mobility and the long photo carrier’s lifetime induced by the dielectric layer.

Solvent treatment was discovered as an efficient anode modification approach to improve the performance of polymer light-emitting diodes. By simply spin-coating several drops of the polar solvent on top of the PEDOT:PSS hole injection layer, the maximum luminance efficiency was increased by as much as 83% without sacrificing the operation voltage. The combination effects of the reduced work function and the lowered resistivity of PEDOT:PSS film, decreased the hole leakage current, leading to a more balanced charge density inside the emission layer, thereby enhancing the device performance.

In the application of polymer light emitting diodes (PLEDs), to prevent etching of ITO by the acidic poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), the pH-neutral PEDOT:PSS was introduced as the hole injection layer (HIL). For the double layer PEDOT:PSS HIL, the pH-neutral PEDOT:PSS on top of ITO stops the indium migration into the polymer, while the regular acidic PEDOT:PSS beneath the light emitting layer keeps the efficient hole injection. The performance of the double layer HIL PLEDs is comparable to or even better than that of the single layer HIL light emitting device. To use pH-neutral PEDOT:PSS as a single layer HIL, the neutral PEDOT:PSS layer was treated by UV and oxygen plasma. Such treatments reduced the hole injection barrier between the HIL and the light emission layer to improve the hole injection, leading to a device performance better than that of the regular acidic PEDOT:PSS HIL device.

Adopting the emerging technology of printed electronics in manufacturing novel ultrathin flat panel displays attracts both academic and industrial interests because of the challenge in the device physics and the potential of reducing production costs. Here we produce all-solution processed polymer light-emitting diode displays by solution-depositing the cathode and utilizing a multifunctional buffer layer between the cathode and the organic layers. The use of ink-jetted conducting nanoparticles as the cathode yields high-resolution cathode patterns without any mechanical stress on the organic layers. The buffer layer, which offers the functions of solvent-proof electron injection and proper affinity, is fabricated by mixing the water/alcohol-soluble polymer and a curable epoxy adhesive. Our 1.5-inch polymer light-emitting diode displays are fabricated without any dead pixels or dead lines. The all-solution process eliminates the need for high vacuum for thermal evaporation of the cathode, which paves the way to industrial roll-to-roll manufacturing of flat panel displays.