Efficient and Bright Blue Perovskite LEDs Enabled by a Carbazole-Phosphonic Acid Interface

Despite the rapid advances of perovskite light-emitting diodes (PeLEDs), achieving high efficiencies at high brightness remains a challenge for blue PeLEDs. Their external quantum efficiencies (EQEs) at luminance settings of ≥1000 cd m–2 are unsatisfactory (normally below 10%), limiting the scope for display applications. Here, we demonstrate blue (∼478 nm) and sky-blue (∼487 nm) PeLEDs with peak EQEs at ≥1000 cd m–2 of 10.3 and 13.6%, respectively, on par with or exceeding those of the state-of-the-art blue PeLEDs. The maximum luminances for the blue and sky-blue devices are 8136 and 18 748 cd m–2, respectively. The high efficiency and brightness are enabled by a carbazole-phosphonic acid hole-transporting interface below the perovskite emissive layer. The interactions between the phosphonic acid and uncoordinated Pb2+ are critical for improving crystallinity and suppressing nonradiative losses at the buried perovskite-charge transporter interface. Our results mark an essential step forward for blue PeLEDs toward display applications.