Da Yin

Efficient and mechanically robust stretchable organic light-emitting devices by a laser-programmable buckling process

Stretchable organic light-emitting devices are becoming increasingly important in the fast-growing fields of wearable displays, biomedical devices and health-monitoring technology. Although highly stretchable devices have been demonstrated, their luminous efficiency and mechanical stability remain impractical for the purposes of real-life applications. This is due to significant challenges arising from the high strain-induced limitations on the structure design of the device, the materials used and the difficulty of controlling the stretch-release process. Here we have developed a laser-programmable buckling process to overcome these obstacles and realize a highly stretchable organic light-emitting diode with unprecedented efficiency and mechanical robustness. The strained device luminous efficiency −70 cd A−1 under 70% strain - is the largest to date and the device can accommodate 100% strain while exhibiting only small fluctuations in performance over 15,000 stretch-release cycles. This work paves the way towards fully stretchable organic light-emitting diodes that can be used in wearable electronic devices.

Highly flexible and efficient top-emitting organic light-emitting devices with ultrasmooth Ag anode.

We demonstrate highly flexible and efficient top-emitting organic light-emitting devices (TOLEDs) by using an ultrasmooth Ag anode. A template-stripping process has been employed to create the ultrasmooth Ag anode on a photopolymer substrate. The flexible TOLEDs obtained by this method keep good electroluminescence properties under a small bending radius and after repeated bending. The efficiency of the flexible TOLEDs is improved by 60% compared with the conventional TOLEDs deposited on Si substrate due to the enhanced hole injection from the ultrasmooth anode.

Highly flexible inverted organic solar cells with improved performance by using an ultrasmooth Ag cathode

Inverted organic solar cells (OSCs) with high efficiency and flexibility have been demonstrated. A thick Ag film with ultrasmooth morphology fabricated on a photopolymer substrate by template-stripping process and a semitransparent Ag film has been employed as cathode and anode of the top-illuminated OSCs, respectively. An improved performance has been obtained compared with that of the OSCs deposited on Si substrate due to the enhanced charge extraction and reduced charge loss resulted from the employment of the ultrasmooth cathode. Moreover, the flexible OSCs obtained by this method keep good performance under a small bending radius and after repeated bending.

Enhanced efficiency of organic light-emitting devices with corrugated nanostructures based on soft nano-imprinting lithography

An enhanced efficiency organic light-emitting device (OLED) with corrugated nanostructures on a small-molecule organic film has been demonstrated. By patterning the hole transport layer via soft nano-imprinting lithography and coating with Ag, a nanostructured cathode is introduced to enhance the light extraction of the OLED without affecting the flatness and conductivity of the indium-tin-oxide film. Both luminance and current efficiency are improved compared with those of conventional planar devices. The observable improvement in luminance and current efficiency can be ascribed to the surface plasmonic and scattering effects caused by the Ag nanostructures. Moreover, theoretical simulations also demonstrate that the power loss to surface plasmon-polariton modes has been recovered.

Mechanically robust stretchable organic optoelectronic devices built using a simple and universal stencil-pattern transferring technology

Stretchable electronic and optoelectronic devices based on controllable ordered buckling structures exhibit superior mechanical stability by retaining their buckling profile without distortion in repeated stretch-release cycles. However, a simple and universal technology to introduce ordered buckling structures into stretchable devices remains a real challenge. Here, a simple and general stencil-pattern transferring technology was applied to stretchable organic light-emitting devices (SOLEDs) and polymer solar cells (SPSCs) to realize an ordered buckling profile. To the best of our knowledge, both the SOLEDs and SPSCs with periodic buckles exhibited the highest mechanical robustness by operating with small performance variations after 20,000 and 12,000 stretch-release cycles between 0% and 20% tensile strain, respectively. Notably, in this work, periodic-buckled structures were introduced into SPSCs for the first time, with the number of stretch-release cycles for the SPSCs improved by two orders of magnitude compared to that for previously reported random-buckled stretchable organic solar cells. The simple method used in this work provides a universal solution for low-cost and high-performance stretchable electronic and optoelectronic devices and promotes the commercial development of stretchable devices in wearable electronics.Fabrication: Buckle up for stretchable optoelectronicsA straightforward technique for producing rumpled ultrathin films enables flexible solar cells and light-emitting diodes to survive up to 20 000 stretch-release cycles. One way researchers are improving the strength of devices such as bendable displays is by carving small, strain-accommodating buckle profiles into polymer surfaces using lasers. Jing Feng from Jilin University in Changchun, China, and colleagues have now simplified this fabrication strategy by deploying stencils to deposit periodic metal patterns onto stretched-out elastomeric substrates. When a polymer film device is attached to this surface, it avoids bonding to the metal regions — a situation that causes the thin organic layer to naturally ripple when the tension is released from the substrate. Experiments revealed that the micron-scale buckles enhanced mechanical robustness by two orders of magnitude compared to conventional stretchable solar cells.

Flexible Efficient Top-Emitting Organic Light-Emitting Devices on a Silk Substrate

A flexible efficient top-emitting organic light-emitting device (TOLED) on an off-the-shelf silk substrate has been demonstrated by planarizing the silk substrate with photopolymer NOA63. The flexibility of the bare silk substrates was retained in the planarized silk substrates due to ductile characteristics of cured NOA63. The planarized silk substrate has shown superiority on surface morphology, which is beneficial to the performances of OLEDs. Their maximum luminance and current efficiency are 45545

Improved efficiency of indium-tin-oxide-free flexible organic light-emitting devices

{\rm{cd/ m}}^{2}

Improved efficiency of indium-tin-oxide-free organic light-emitting devices using PEDOT:PSS/graphene oxide composite anode

and 37.7 cd/A, respectively. Moreover, our devices show not only high luminance and efficiency but also high flexibility and mechanical robustness. Emission of operating devices is uniform and free of defects under a very small bending radius and the luminance and efficiency do not deteriorate obviously after repeated bending. TOLEDs on silk substrate are a potential alternative to wearable displays.