A Tri‐Spiral‐Mediated Spatial Hybrid LRCT/SRCT Strategy for High‐Efficiency Narrowband Blue Emitters

ABSTRACT

The conventional hybrid strategy that directly links long‐range charge‐transfer (LRCT) and short‐range charge‐transfer (SRCT) units through a single bond inevitably induces an uncontrollable electron push–pull effect, resulting in emission redshift and spectral broadening. In this study, we propose a spiro‐mediated spatial decoupling strategy that bridges an LRCT‐type donor–acceptor fragment and an SRCT‐type multiple‐resonance (MR) fragment through a nonconjugated tri‐spiral skeleton for the first time. This design effectively interrupts the π‐conjugation between the two units, allowing the LRCT fragment to introduce additional reverse intersystem crossing (RISC) channels without perturbing the MR core. As a result, a 16‐fold enhancement in RISC rate is achieved relative to the MR prototype while preserving narrowband emission. TRZN//NBO exhibits an emission peak of 473 nm with a narrow full width at half maximum of 24 nm in toluene and a fast RISC rate of 1.26 × 10 ⁵ s ⁻¹ . The corresponding device achieves a maximum external quantum efficiency (EQE) of 36.1%, retaining high EQEs of 28.2% and 21.0% at luminance of 100 and 1000 cd m ⁻² , respectively. These results demonstrate that the spiro‐mediated spatial hybrid LRCT/SRCT strategy offers a promising route to circumvent the trade‐off between efficiency and color purity in narrowband emitters.