Impact Of Photon Recycling On Carrier Recombination Processes In Ch3nh3pbbr3 Single Crystals Revealed By Time-Resolved Two-Photon-Excitation Microscopy

Recently, lead-halide perovskites CH 3 NH 3 PbX 3 (X = I, Br, and Cl) are attracting considerable attention as a new class of photonic device materials. Especially in case of thin-film solar cells based on perovskite CH 3 NH 3 PbI 3 , the high power conversion efficiency (exceed 22%) has been already achieved and to attain the long-term stability and large-area device fabrication become major research topics to realize practical application for perovskite solar cells. The outstanding properties of CH 3 NH 3 PbX 3 such as large absorption coefficients, long-lived free-carriers, and large carrier diffusion lengths are considered to be the reasons for the high solar-cell efficiencies [1]. In addition, CH 3 NH 3 PbX 3 perovskites show extremely high luminescence efficiencies and unique optical phenomena such as photon recycling (photoemission and reabsorption processes) recently discovered in CH 3 NH 3 PbI 3 [2] and CH 3 NH 3 PbBr 3 [3]. Photon recycling is a very important optical process determining the external quantum efficiencies of solar cells and light-emitting diodes. To achieve further improvements of performance in CH 3 NH 3 PbX 3 -based photonic device, the fundamental optical responses are needed to be clarified.