Perovskite Phase Analysis by SEM Facilitating Efficient Quasi‐2D Perovskite Light‐Emitting Device Designs

Abstract The performance of quasi‐2D perovskite light‐emitting devices (PeLEDs) has been greatly improved in the past several years. Characterizations such as transient absorption (TA) spectroscopy and absorption spectra have been widely adopted to confirm the phases in the quasi‐2D perovskite layers. However, all the above‐mentioned characterization techniques could only identify the n values of phases without providing information on the distribution of phases. Here, phase distributions on the quasi‐2D perovskite surfaces are identified by utilizing the charging effect during the scanning electron microscope (SEM) measurement. Then, compositional and antisolvent engineering are adopted to improve the quality of quasi‐2D perovskite films. Green PeLEDs with an external quantum efficiency (EQE) of >20% are achieved with more uniform condensed film morphology and proper phase distribution. The work shows that SEM measurement is a powerful tool for studying the phase distribution on the quasi‐2D perovskite surfaces.