Controlling the crystallization processes and energy-level alignment in perovskite emitters is crucial for realizing high-performance light-emitting diodes (LEDs) because these factors directly govern the radiative recombination efficiency. Here, we introduce benzylphosphonic acid (BPA) as a directive molecular template that directs the morphological evolution of perovskite materials, first forming two-dimensional (2D) nanoplatelets (NPLs), which then serve as structural scaffolding for the subsequent formation of a compact, pinhole-free film. Density functional theory (DFT) simulations reveal that BPA not only exhibits a strong binding affinity to the perovskite precursor, but also possesses the highest occupied molecular orbital (HOMO) level optimally aligned with the valence band maximum (VBM) of CsPbBr3. This dual capability enables BPA to function both as a crystal-regulating agent guiding NPL growth and as an effective electron-blocking interlayer at the hole transport interface. The resulting perovskite films exhibit enhanced crystallinity and photoluminescence quantum yield. Consequently, BPA-assisted green PeLEDs achieve a remarkable peak external quantum efficiency (EQE) of 26.42% and a maximum luminance of ∼50,100 cd m-2. Notably, this approach is universally applicable, improving the EQE of blue-emitting CsPbCl1.5Br1.5 PeLEDs from 3.29% to 10.24%. These findings highlight the promise of molecule-level interfacial engineering in perovskite morphology control and device performance.
Zeng et al. (Fri,) studied this question.