Enhanced Brightness Through Rational Design of Hole Transport Layer for Blue Perovskite Light‐Emitting Diodes

ABSTRACT State‐of‐the‐art blue lead‐halide perovskite light‐emitting diodes (PeLEDs) suffer from low brightness and short lifetime, which constitutes a critical bottleneck for the development of full‐color perovskite displays. A major performance bottleneck originates from the considerable hole injection barrier at the interface of hole‐transporting layers (HTLs) and blue perovskite emissive layers. To address this, we propose a non‐protic interfacial modification strategy, by designing and synthesizing two novel organic small molecules – 9,9‐dibutyl‐N 2 ,N 2 ,N 7 ,N 7 ‐tetrakis(4‐methoxyphenyl)‐9H‐fluorene‐2,7‐diamine (MPFO) and 9,9‐bis(3‐(dimethylamino)propyl)‐N 2 ,N 2 ,N 7 ,N 7 ‐tetrakis(4‐methoxyphenyl)‐9H‐fluorene‐2,7‐diamine (MPFO‐MAP)—to modify the poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) HTL. MPFO‐MAP, with terminal dimethylamino groups, concurrently reduces the hole‐injection barrier, accelerates hole transport, thereby balancing electron and hole current, while passivates PEDOT:PSS/perovskite interfacial defects to enhance radiative recombination. The MPFO‐MAP modified blue PeLED achieves a maximum luminance of 8272 cd/m 2 and a champion external quantum efficiency of 12.6%, representing 2.9‐fold and 3.7‐fold improvements over the pristine PEDOT:PSS device, respectively. This dual‐function non‐protic interfacial engineering strategy provides a versatile molecular design blueprint for high‐brightness blue PeLEDs and can be extended to other perovskite‐based optoelectronic devices, facilitating their practical application.