Quasi-2D Ruddlesden-Popper perovskites receive tremendous attention for application in light-emitting diodes (LEDs). However, the role of organic ammonium spacers on perovskite film has not been fully-understood. Herein, a spacer cation assisted perovskite nucleation and growth strategy, where guanidinium (GA + ) spacer is introduced into the perovskite precursor and at the interface between the hole transport layer (HTL) and the perovskite, to achieve dense and uniform perovskite films with enhanced optical and electrical performance is developed. A thin GABr interface pre-formed on HTL provides more nucleation sites for perovskite crystal; while the added GA + in perovskite reduces the crystallization rate due to strong hydrogen bonding interacts with intermediates, which promotes the growth of enhanced-quality quasi-2D perovskite films. The ionized ammonium group (NH 3 +) of GA + also favors formation of polydisperse domain distribution, and amine or imine (NH 2 or NH) group interact with perovskite defects through coordination bonding. The spacer cation assisted nucleation and growth strategy is advantageous for producing efficient and high-luminance perovskite LEDs, with a peak external quantum efficiency of over 20% and a luminance up to 100 000 cd m −2 . This work can inform and underpin future development of high-performance perovskite LEDs with concurrent high efficiency and brightness.

The interface state between the hole transport layer (HTL) and the quantum dots (QDs) plays a crucial role in the optoelectronic performance of light-emitting diodes. Herein, we reported an efficient...

Perovskite light-emitting diodes (PeLEDs) are regarded as exceptional candidates for next-generation high-definition displays. Despite the fact that the all-inorganic perovskites possess an advantage in structural stability among the perovskite family, the electroluminescence (EL) performance of their corresponding PeLEDs are still challenged by the difficulties in depositing smooth, uniform perovskite films and realizing chare balance under working voltages. Here, we report an efficient and stable CsPbBr3 based PeLED, which is enabled by a hole transport layer (HTL) of KBr doped poly(3,4,-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The KBr dopant can not only improve the charge balance by boosting the hole injection, but also suppress the exciton quenching through passivating halide defects in perovskites. The resulting PeLED exhibits a maximum current efficiency (CE) of 35.09 cd A−1 and a maximum external quantum efficiency (EQE) of 10.02%, which are over 12-fold higher than those of the control device based on undoped HTL, respectively. Our work provides an easy and efficient strategy to boost the EL performance of all-inorganic perovskites.