【Nature】北大严纯华院士、周欢萍、孙聆东|原位纳米晶限域网络破解蓝光钙钛矿难题，实现21.8%超高外量子效率与11纳米尺寸精准控制#

a, Schematic of ligand design and crystallization of perovskite nanocrystals. The coordinated polymerizable monomer suppresses the nucleation process and the in situ-formed polymer network further restrains the growth of perovskite nanocrystals, which induces small and stable nanocrystals. b–f, Transmission electron microscopy images of perovskite nanocrystals without additives (b), with P-MOA (c), with OEGA (d), with MPEG-MAA (_M_n = 1,000) (e) and with MPEG-MAA (_M_n = 5,000) (f). g, The electron energy loss spectra (EELS) acquired from the positions highlighted in the inset high-angle annular dark-field scanning transmission electron microscopy image. O-K and Cs-L denote the EELS edges corresponding to the oxygen K-shell and caesium L-shell, respectively. h,i, High-resolution transmission electron microscopy images of the pristine (h) and OEGA perovskites (i). Insets: corresponding fast Fourier transform diffractograms and atomic structure model. j, X-ray diffraction patterns of the pristine and OEGA perovskites. θ denotes the Bragg angle. ZA, zone axis. Scale bars, 1 μm (b); 100 nm (c–f); 20 nm (g(inset),h); 5 nm−1 (h(inset)); 5 nm (i); 10 nm−1 (i(inset)).#

a, 1H NMR spectra of OEGA/PbBr2 before and after thermal annealing (POEGA). b, Pb 4_f_ X-ray photoelectron spectroscopy spectra of the pristine and OEGA perovskites. The X-ray photoelectron spectroscopy spectra are calibrated to the adventitious C 1_s_ peak at 284.8 eV. c,d, In situ absorption (c) and photoluminescence (d) evolution of the pristine and OEGA perovskites during the crystallization process. The colour bars in c and d indicate the signal intensity (a.u.). e, Schematic of the nucleation and crystallization of pristine and OEGA perovskites. f,g, Transmission electron microscopy images and fast Fourier transform diffractograms of FAPbI3 without (f) and with (g) OEGA. Scale bars, 500 nm (f); 5 nm−1 (f(inset),g(inset)); 200 nm (g).#

a,b, Integrated photoluminescence intensity (a) and FWHM (b) from temperature-dependent photoluminescence spectra against measuring temperatures. The symbols are the extracted experimental data and the solid lines are the best least-squares fit. c, Raman spectra of the pristine and OEGA perovskite films after normalization for sample concentration. Inset: atomic structure model representing longitudinal-optical vibration. d–f, Time-resolved photoluminescence decay (d), steady-state photoluminescence spectra (e) and excitation intensity-dependent PLQY (f) of pristine, OEGA and OEGA/PEA perovskites. The decays in d were normalized to their maximum intensity and rescaled to 1,000 for clarity.#

得益于空间限域与高结晶度的协同效应，所得钙钛矿纳米晶薄膜表现出极其优异的发光性能，其荧光量子产率（PLQY）飙升至83%，并在低激子密度下即表现出饱和趋势。将其应用于蓝光PeLED器件的构筑中，在491纳米的纯蓝光发射下实现了高达21.8%的峰值外量子效率（EQE），最大亮度达到1925 cd m⁻²，处于国际顶尖水平。同时，原位形成的POEGA交联网络在钙钛矿晶界处构筑了坚固的离子迁移屏障，将器件的离子迁移活化能由0.27 eV显著提升至0.77 eV。这种结构上的强化使器件的工作寿命（$T_{50}$）延长至69.4分钟，并在高偏置电压下展现出极佳的光谱与运行稳定性。

a, Energy diagram of each layer in PeLEDs. b, CIE coordinates of OEGA/PEA PeLEDs. c–e, Current density–voltage (c), luminance–voltage (d) and EQE–current density (e) curves of PeLED devices. f, Histogram of 32 devices for the pristine and OEGA/PEA PeLEDs. g, Operational stability of PeLEDs with an initial luminance around 100 cd m–2. Inset: electroluminescence spectra of OEGA/PEA PeLEDs at different bias voltages. h, Temperature-dependent conductivity measurements of the pristine and OEGA/PEA perovskite films. ITO, indium tin oxide.#