Search

Quasi‐2D perovskite materials have promise to unlock the full potential of blue perovskite light‐emitting diodes (PeLEDs). However, the efficiency of blue emissive PeLEDs still lags behind the green‐ and red‐emitting counterparts. Here, a multifunctional passivating molecule of (2‐(3,6‐dichloro‐9H‐carbazol‐9‐yl)ethyl)phosphonic acid (36ClCzEPA) that can form a self‐assembled monolayer (SAM) on the indium tin oxide (ITO) electrode is reported. The 36ClCzEPA SAM facilitates hole injection by increasing the work function of ITO through the strong interfacial dipole layer formation at the interface between the perovskite emitter and the ITO electrode. Moreover, it allows a pure‐blue emission and reduces the exciton quenching of luminescence in the perovskite emitter considerably because of its neutral nature, compared to the commonly used acidic PEDOT:PSS. Furthermore, chlorine atoms in the 36ClCzEPA promote well‐ordered crystalline 2D perovskite phases and decrease interfacial trap‐assisted deactivation channels by interfacial passivation. These beneficial characteristics of the 36ClCzEPA SAM yield the excellent luminescence property of PeLEDs with a maximum luminance of 1253 cd m−2 and a peak external quantum efficiency of 4.80% at 473 nm. This work demonstrates that a well‐designed molecule forming an interfacial SAM can be an important component for enhancing the luminescence property of pure‐blue PeLEDs. [ABSTRACT FROM AUTHOR]

• Incorporation of hydroxyl group-containing additives induces the PEDOT:PSS substrate to have a higher surface polarity. • On the PEDOT:PSS substrate having a higher polarity, lower- n -dominated phase distribution induces a hypsochromically shift of the luminescence spectrum. • Efficient PeLEDs are achieved with an EQE of 5.57% at a hypsochromically-shifted EL spectrum of 472 nm wavelength. Quasi-two-dimensional (quasi-2D) perovskites are composed of self-organized multiple-quantum-well structures. Imbalanced crystallization during the solution-processed deposition results in the formation of different 2D phases, which are affected by the surface polarity of substrates. Herein, we investigate the influence of the surface polarity of the underlying hole injection layer (HIL) on the crystallization dynamics of each 2D phase and the luminescence properties of resulting quasi-2D perovskite films. Incorporating L-dopa involving hydroxyl groups into the HIL gives the substrate a higher surface polarity, allowing the decrease in the critical free energy of nucleation. This HIL ensures the formation of dense nuclei involving a small-sized nucleus, which enables the quasi-2D perovskite film to entail a lower- n -dominated phase distribution. The modulated phase distribution eventually induces a hypsochromically shifted luminescence spectrum. Furthermore, by controlling the ratio of L-phenylalanine and L-dopa, efficient perovskite light-emitting diodes (PeLEDs) having well-matched electronic structure and pure-blue perovskite emitter are realized with a maximum external quantum efficiency of 5.57% at 472 nm. This work provides a facile approach to achieving efficient pure-blue PeLEDs. [ABSTRACT FROM AUTHOR]