Abstract

Recently, lead-halide perovskites CH₃NH₃PbX₃ (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 CH₃NH₃PbI₃, 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 CH₃NH₃PbX₃ 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, CH₃NH₃PbX₃ perovskites show extremely high luminescence efficiencies and unique optical phenomena such as photon recycling (photoemission and reabsorption processes) recently discovered in CH₃NH₃PbI₃ [2] and CH₃NH₃PbBr₃ [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 CH₃NH₃PbX₃-based photonic device, the fundamental optical responses are needed to be clarified.

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