High performance organic ultraviolet photodetector with efficient electroluminescence realized by a thermally activated delayed fluorescence emitter

Abstract

A high performance organic ultraviolet (UV) photodetector with efficient electroluminescence (EL) was obtained by using a thermally activated delayed fluorescence (TADF) emitter of (4s,6s)-2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN). An exciton adjusting layer (EAL) was delicately designed to construct an energy-level-aligned heterojunction with 4CzIPN. As a result, the bi-functional device exhibited a high detectivity of 1.4 × 1012 Jones under 350 nm UV light. Moreover, our device exhibited efficient EL emission utilizing the merit of reverse intersystem crossing process from triplet to singlet excitons of 4CzIPN, showing a maximum luminance, current efficiency, and power efficiency of 26370 cd/m2, 8.2 cd/A, and 4.9 lm/W, respectively. This work arouses widespread interest in constructing efficient bi-functional device based on TADF emitter and EAL structure.

An S-shaped double helicene showing both multi-resonance thermally activated delayed fluorescence and circularly polarized luminescence

“…Beyond chiroptical properties the high solubility of helicenes in organic solvents (compared to planar acenes), coupled with their excellent thermal stability has led to a wider array of optoelectronic applications, including as hole-transport materials in photovoltaic devices. [26][27][28] Thermally activated delayed fluorescence (TADF) materials have become increasingly attractive as sensors, 29 in lasers, 30 photodetectors, 31 photocatalysis 32 and bioimaging 33 as well as both emitters and hosts in organic light-emitting diodes (OLEDs) 34 due to their ability to harvest 100% of electrically generated excitons to generate light. This is accomplished by conversion of triplet excitons into singlets via reverse intersystem crossing (RISC) [34][35][36][37][38] enabled by their small S 1 -T 1 energy gap, DE ST .…”

“…Thermally activated delayed fluorescence (TADF) materials have become increasingly attractive as sensors, 29 in lasers, 30 photodetectors, 31 photocatalysis 32 and bioimaging 33 as well as both emitters and hosts in organic light-emitting diodes (OLEDs) 34 due to their ability to harvest 100% of electrically generated excitons to generate light. This is accomplished by conversion of triplet excitons into singlets via reverse intersystem crossing (RISC) 34–38 enabled by their small S 1 –T 1 energy gap, Δ E ST .…”

Balanced Carrier Injection and Charge Separation of CuInS2 Quantum Dots for Bifunctional Light-Emitting and Photodetection Devices

“…With the increasing demand for miniaturization, portability, and multifunctionalization of electronics, the integration degree of electronic devices has been continuously improved, and unit devices that can realize more than one function begin to emerge, which is not only space-saving but also beneficial to the development of novel applications . Among multifunctional devices, the integrated light-emitting and photodetection device is quite attractive, which has the potential for micro light communication and intelligent sensing. − Because the mechanisms of electroluminescence and photodetection are just opposite to each other, the realization of bifunction requires delicate designs for not only the active layer materials but also the device band structures. − …”

Recent advances in thermally activated delayed fluorescence for white OLEDs applications

“…Typically, the dendrimer is constructed by a triphenyl-s-triazine acceptor core and multiple donor carbazoles, whereas a TADF core and carbazole dendrons are connected by flexible aliphatic chains which demonstrate better optical properties [142]. Importantly, the organic ultraviolet detectors [146], fluorescence probes [147][148][149], and TTA sensitizers [150][151][152][153][154][155] have been prepared by using small ΔE ST and efficient RISC process of TADF materials with respective molecular structure.…”