Spirofluorene adamantane-modified anthracene-based emitters enable efficient deep-blue non-doped OLEDs

Abstract

The development of highly efficient and stable deep-blue light-emitting materials remains a significant challenge in the field of organic optoelectronics. This paper presents a novel molecular design strategy for deep-blue light-emitting materials, addressing the critical need for highly efficient non-doped organic light-emitting diodes (OLEDs) with blue color coordinates (0.14, 0.08) that meet the National Television System Committee (NTSC) standard. In this study, we designed and synthesized two innovative anthracene-based luminescent materials, SAd-AnCN and SSAd-AnCN, incorporating two site-resistive heterostructures. These materials leverage the substantial spatial site resistance of adamantane and the high luminescence efficiency of anthracene benzyl cyanide. Comprehensive photophysical properties and crystallographic studies revealed that the introduction of adamantane effectively suppresses the formation of luminescent clusters. The photoluminescence (PL) spectra of the neat films were found to be entirely consistent with those in solution, accompanied by high photoluminescence quantum yields (PLQYs). Non-doped OLED devices fabricated using SAd-AnCN and SSAd-AnCN as the emissive layer materials exhibited outstanding electroluminescence (EL) performance. The devices achieved maximum external quantum efficiencies (EQE_max) of 5.9% and 4.8%, with CIE coordinates of (0.149, 0.077) and (0.151, 0.062), respectively. Transient electroluminescence (Tr-EL) spectra analysis indicated that the triple–triple-state annihilation (TTA) process has a negligible contribution to the EL process. The high exciton utilization efficiency (EUE) is primarily attributed to the efficient thermal exciton channel. This work not only highlights the potential of SAd-AnCN and SSAd-AnCN in deep-blue non-doped OLEDs but also offers a valuable strategy for the design of efficient and stable new deep-blue fluorescent materials. Our findings pave the way for future advancements in the development of high-performance deep-blue OLEDs, contributing to the broader field of organic optoelectronics.