Phase Control and Defect Passivation via (2-Aminoethyl)phosphonic Acid-Modified PEDOT:PSS for Blue Perovskite Light-Emitting Devices

Achieving pure blue emission of perovskite light-emitting diodes (PeLEDs) is of great importance for fulfilling full-color display and lighting applications. However, achieving high-performance pure blue PeLEDs in pure bromide quasi-2D (Q2D) perovskites has always been a formidable challenge. Here, an interface engineering strategy is proposed to regulate the light emission color and device photoelectric performance simultaneously by employing (2-aminoethyl)phosphonic acid (AEP)-modified poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). The AEP-PEDOT:PSS not only enhances the wettability toward the perovskite precursor but also coordinates with the unsaturated Pb atoms, facilitating the growth of nanocrystals with fewer defects. Thereby, pure blue emission shifted from the sky-blue region with a higher PLQY was achieved. Additionally, the incorporation of AEP reduces the conductivity of the PEDOT:PSS film, enabling a more balanced charge transport in the device. Consequently, the pure blue light-emitting PeLEDs with AEP modification achieve an external quantum efficiency (EQE) of 5.2%, approximately 1.9 times that of the control device. Our findings may provide valuable insights and helpful guidance for the development of Q2D pure blue perovskite LEDs.