Copper-based Perovskites with Horizontal Transition Dipole Moment for Highly Efficient Light-emitting Diodes

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Halide perovskites are poised to revolutionize the LEDs display technology for their extraordinary optoelectronic properties, such ashigh colour purity, easy solution processibility, nearly 100% photoluminescence quantum yield (PLQY), and broad light emissiontunability. However, to realize the practical applications of perovskite LEDs in display and lighting technology, some key issues, suchas the presence of toxic lead in most emissive perovskites and the weak stability of typical perovskite LEDs, must be solved. Copper-basedperovskites, especially the blue emissive Cs3Cu2I5, are one of the most promising lead-free perovskite families for their lowtoxicity, remarkable PLQY, and excellent stability. Nevertheless, the record external quantum efficiency (EQE) of Cs3Cu2I5 blue LEDs isonly 1.12%. In this proposal, we will improve the light outcoupling efficiency of copper-based perovskite LEDs by controlling thetransition dipole moment orientation of the emissive layers. Copper-based perovskite thin films with dominated horizontal transitiondipole moments will be fabricated by synthesizing their ultrathin nanoplates and assembling these nanoplates into thin films.Copper-based perovskite LEDs with these thin films as emissive layers will be manufactured and theoretically investigated with thefinite-difference time-domain (FDTD) method. By doing so, we aim to break the record for the EQE of copper-based perovskite LEDswith an EQE surpassing 10% in blue LEDs and surpassing 4% in white LEDs.