2, Princeton University, Princeton, New Jersey, United States
Electrically-pumped lasing remains an elusive grand challenge for the organic and thin film electronics community. Recently, hybrid organic-inorganic perovskites have emerged as promising gain media for tunable, solution-processed semiconductor lasers, sparking interest in the use of these materials for an eventual diode laser. However, continuous-wave (CW) operation, which is considered a key stepping stone to electrically-pumped lasing, has not been achieved to date. Previous work has shown that lasing from methylammonium lead iodide (MAPbI3) perovskite in its tetragonal phase at temperatures T>160 K undergoes an as-yet-unexplained lasing death phenomenon within ~100 ns following turn-on of the pump.
Here, we demonstrate that optically-pumped CW lasing can be realized in MAPbI3 distributed feedback lasers that are maintained below the MAPbI3 tetragonal-to-orthorhombic phase transition temperature, T~160 K. At a substrate temperature of 102 K, these lasers achieve threshold at a pump intensity of Ith~17 kW/cm2 and sustain CW lasing with a clear output beam for over one hour. Importantly, although transient absorption measurements indicate that the bulk of the perovskite films exist in the orthorhombic phase, we find that CW gain and lasing originates from the tetragonal phase at an emission wavelength λ~785 nm. We propose that small tetragonal phase inclusions are photogenerated by the pump and may act as charge carrier sinks within the larger-bandgap orthorhombic phase host matrix, enhancing population inversion in a fashion analogous to host–guest organic– semiconductor gain media and inorganic quantum wells. These results suggest a general strategy to design perovskite gain media for CW lasing and represent a key step toward the ultimate goal of a perovskite laser diode.