A high-performance hyperfluorescent device through host optimization

Abstract

The unsatisfied feature in the operating lifetime and efficiency has hindered the wide application of hyperfluorescent organic light emitting diodes (OLEDs). In order to achieve high efficiency and long lifetime, it is necessary to ensure the stability of the emitting layer (EML) while maintaining high exciton utilization. However, this faces enormous challenges. Our research reveals the impact of host characteristics on the efficiency and lifetime, in a typical hyperfluorescent system. The experimental results show that the carrier mobility and triplet states (T1) of host seriously affect device performance. Strategically adjusting exciton recombination through host selection, can help achieve an efficient and stable device. In addition, the stability of assistant layers adjacent to EML, also has influence on the lifetime of the devices. On this basis, a high-performance green hyperfluorecent device was fabricated, with a maximum efficiency of 227.7 cd A−1. The LT95 (brightness attenuation to 95%) lifetime of such device achieved to 410 h with an initial brightness of 31338 cd m−2, creating a new record. The performance of this hyperfluoresent OLED has reached the same level as the latest generation of commercial phosphorescent devices. More than that, the color of CIE-1931 (0.205, 0.757) of the device well meets the requirement of Adobe standard for green. In addition, a low efficiency roll-off of 1.07%, from maximum efficiency to efficiency at 10 mA cm−2, was observed, which helped to reduce the power consumption of OLED high gray display.The purposeful adjustment of the position and width of exciton recombination region by a well-chosen host, is considered the main reason for achieving such excellent performance. This study systematically reveals the influence of host on OLEDs based on thermally activated delayed fluorescence (TADF), and shows a great possibility of the technology in practical application.