Mixed halide 3D perovskites are promising for bright, efficient, and wide-color gamut light-emitting diodes (LEDs) due to their excellent carrier transport, high luminescence, and easily tunable bandgaps. However, serious halide ion migration inside mixed halide 3D perovskite results in poor operational and spectral stability of the as-fabricated LEDs. Here, a hetero-nucleation crystallization strategy is reported to grow [111]-orientation preferred mixed halide 3D perovskite CsPbI 3-x Br x thin films for stable pure red LEDs. This hetero-nucleation crystallization is enabled by the addition of phosphoric acid (H 3 PO 4 ) complexation, which promotes the growth of small perovskite grains into large grains with uniform [111]-orientation. The obtained [111]-orientation preferred film exhibits excellent stability under light or electric field stimulus as revealed by model analysis and experimental results compared to that of [001]-orientation preferred film. Thus, based on the [111]-orientation preferred film, the fabricated LED exhibits an external quantum efficiency of 22.8%, a maximum brightness of 12 000 cd m −2 , and a half-life time of 4080 min under 1.5 mA cm −2 . More importantly, the electroluminescence spectrum of the device remains stable during the continuous operation of 4080 min, showcasing the significant spectral stability improvement enabled by the hetero-nucleation induced [111]-orientation strategy.
Gang Chen,Xue Bai,Cong Ji,Zhijun Zhou,Zixuan Zhang,Chao Chen,Zhengtang Su,Wei Cai,Rongli Gao,Chunlin Fu
Bi 0.5 Na 0.5 TiO 3 ceramic is a promising dielectric energy storage material due to its high spontaneous polarization (> 40 μC/cm 2 ) . Although many studies have been carried out to enhance the energy storage performance of Bi 0.5 Na 0.5 TiO 3 ceramic, achieving better energy storage performance is still a considerable challenge. Herein, Bi 0.5 Na 0.5 TiO 3 -BiYbO 3 -SrTiO 3 (BNT-BY-STO) relaxor ferroelectric ceramics were constructed, and <111>-oriented (1- x )(0.99BNT-0.01BY)- x STO ceramics were successfully fabricated by a templated grain growth method. The moderate energy storage performance (the reversible energy storage density of 3.26 J/cm 3 and energy storage efficiency of 76.3% under 290 kV/cm) can be achieved in <111>-oriented 0.8(0.99BNT-0.01BY)-0.2STO ceramics. The enhanced energy storage performance of textured BNT-BY-STO ceramics could be mainly attributed to the grain refinement of STO, and the improved breakdown strength and relaxation behavior caused by orientation engineering. These findings demonstrate that the co-doping of BY and STO and orientation engineering are effective strategies for improving the energy storage performance of BNT ceramic.
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