Efficient Near‐Infrared (NIR) Organic Light‐Emitting Diodes Based on Donor–Acceptor Architecture: An Improved Emissive State from Mixing to Hybridization

Herein, a high‐efficiency near‐infrared (NIR) material PXZ‐3‐NZP is designed and sythesized using the concept of hybridized local and charge‐transfer (CT) state (HLCT), which is composed of donor (D) and acceptor (A) moieties as well as 10‐substituted isomeride PXZ‐10‐NZP for the purpose of comparison and deep understanding on the essential difference of their excited state properties. As a result, the nondoped electroluminescent (EL) device of PXZ‐3‐NZP exhibits an excellent NIR emission (λmax = 738 nm) with a maximum external quantum efficiency (ηEQE) of 0.82% and a Commission International de L'clairage coordinate of (0.70, 0.29), which is record‐setting among NIR fluorescent organic light emitting diodes with similar EL chromaticity. Also, a high ηEQE of 2.03% is achieved in a doped device with a deep red emission at λmax = 676 nm. As a comparison, PXZ‐10‐NZP shows far inferior performance to those of PXZ‐3‐NZP in both nondoped and doped devices, due to the instinct CT character of its S1 excited state. In terms of excited state, HLCT state is exactly superior to mixed state in high‐efficiency luminescence, which is a particularly useful strategy to design narrow‐bandgap light‐emitting materials beyond energy gap law with donor–acceptor architectures. Two near‐infrared (NIR) molecules (PXZ‐3‐NZP and PXZ‐10‐NZP) using the same donor and acceptor moieties with different linkages are synthesized and characterized. And a very high ηEQE of 0.82% is achieved in nondoped device of PXZ‐3‐NZP with an NIR emission at λmax = 738 nm, which indicates that hybridized local and charge‐transfer is more useful state than mixing state to design narrow‐bandgap light‐emitting materials beyond energy gap law with donor–acceptor architectures.