A facile synthesis of segmented silver nanowires and enhancement of the performance of polymer solar cells.

In this work, segmented silver nanowires (AgNWs) with an average diameter of 60 nm have been successfully synthesized by a typical polyol method without any templates and seeds. The synthesized segmented AgNWs were strongly dependent on the reaction temperature and time. It was found from high-resolution transmission electron microscopy and selected area electron diffraction measurements that the connection node of segmented AgNWs was in the form of a twinned crystal. We speculated that these segmented AgNWs were possibly derived from end-to-end self-connection and self-concrescence of two neighbouring Ag nanorods or nanowires at a suitable reaction temperature and time, which is further confirmed by the secondary growth of AgNWs. In addition, segmented AgNWs were blended into hole transporting layers to enhance the performance of polymer solar cells (PSCs) by utilizing their localized surface plasmon resonance and optical scattering effects. As a result, the power conversion efficiency (PCE) and short-circuit current density (Jsc) of PSCs with segmented AgNWs increased from 2.81% and 8.99 mA cm-2 to 3.30% and 9.95 mA cm-2, respectively.

Efficient Quantum-Dot Light-Emitting Diodes Employing Thermally Activated Delayed Fluorescence Emitters as Exciton Harvesters.

Utilization of triplet excitons plays a key role in obtaining highly efficient quantum-dot light-emitting diodes (QD-LEDs). However, to date, only phosphorescent materials have been implemented to harvest triplet excitons in QD-LEDs. In this work, we introduced a thermally activated delayed fluorescence (TADF) emitter, 4,5-di(9H-carbazol-9-yl)phthalonitrile (2CzPN), doped into poly(N-vinylcarbazole) (PVK) as an exciton harvester in red QD-LEDs by solution processing. As a result, electrons leaking to the PVK layer will be trapped by 2CzPN to form long-lifetime TADF excitons in the 2CzPN:PVK layer, and then this harvested exciton energy can be effectively transferred to the adjacent QDs by the Förster resonance energy-transfer process. The fabricated red CdSe/CdS core/shell QD-LEDs show a maximum luminescence efficiency of 17.33 cd/A and longer lifetime. Our results demonstrate that the TADF sensitizer would be a promising candidate to develop highly efficient QD-LEDs.