Amplified Spontaneous Emission Based on 2D Ruddlesden-Popper Perovskites

2D Ruddlesden-Popper perovskites (RPPs) are a class of quantum-well (QW) materials, composed of layered perovskite QWs encapsulated between two hydrophobic organic layers. Different from widely investigated 3D-perovskites with free carriers at room temperature, 2D-RPPs exhibit strongly bound electron-hole pairs (excitons) for high-performance solar cells and light emitting diodes (LEDs). Herein, it is reported that self-organized multiple QWs in 2D-RPP thin films naturally form an energy cascade, which enables an ultrafast energy transfer process from higher energy-bandgap QWs to lower energy-bandgap QWs. Therefore, photoexcitations are concentrated on lower-bandgap QWs, facilitating the build-up of population inversion. Room-temperature amplified spontaneous emission (ASE) from 2D-RPP thin films is achieved at dramatically low thresholds, with gain coefficients as high as >300 cm(-1), and stoichiometrically tunable ASE wavelengths from visible to near-infrared spectral range (530-810 nm). In view of the high efficiency reported for LEDs, these solution-processed 2D-RPP thin films may hold the key to realize electrically driven lasers.