Fu Xiaoming, Peng Zhiwei, Zhang Chi, Xia Yong, Zhang Jianbing, Luo Wei, Guo L Jay, Li Honglang, Wang YuHuang, Zhang Daoli
School of Optical and Electronic Information, Huazhong University of Science and Technology 1037 Luoyu Road, Hongshan District Wuhan City Hubei Province 430074 P. R. China
School of Physics, Communication and Electronics, Jiangxi Normal University 99 Ziyang Avenues Nanchang City Jiangxi Province 330022 P. R. China.
RSC Adv. 2018 Jan 3;8(2):1132-1139. doi: 10.1039/c7ra11832e. eCollection 2018 Jan 2.
Organometal halide perovskite nanocrystals hold vast potential for application in photovoltaics, light emitting diodes, low-threshold lasers, and photodetectors due to their size-tunable bandgap energies and photoluminescence as well as excellent electron and hole mobilities. However, the synthesis of such nanocrystals typically suffers from poor structural stability in solution and the coexistence of lamellate nanocrystals (nanoplatelets) and spherical nanocrystals (nanoparticles). Here we show that the pure nanoparticle morphology of CHNHPbBr nanocrystals can be realized by employing lead oleate (Pb(CHCOO)) as the sole lead source and controlled using short- and long-chain mixed alkyl ammonium. These nanocrystals are monodispersed (2.2 ± 0.4 nm in diameter), highly fluorescent (with a quantum yield approaching 85%), and highly stable in the solution (for more than 30 days). Comparative studies reveal that the shape of CHNHPbBr nanocrystals is strongly dependent on the lead source, PbBr and Pb(CHCOO), and evolves as a function of the ratio of short- and long-chain alkyl ammoniums in the precursors. At an optimal short to long-chain alkyl ammonium ratio of 4 : 6, the growth of CHNHPbBr nanoplatelets can be selectively suppressed with Pb(CHCOO) as the sole lead source, enhancing the overall photoluminescence quantum yield of the produced CHNHPbBr nanocrystals. This work reveals important new insights for controlled synthesis of perovskite nanocrystals with pure crystal shape and significantly improved photoluminescence properties and stability.
有机金属卤化物钙钛矿纳米晶体因其尺寸可调的带隙能量、光致发光以及出色的电子和空穴迁移率，在光伏、发光二极管、低阈值激光器和光电探测器等领域具有巨大的应用潜力。然而，此类纳米晶体的合成通常在溶液中结构稳定性较差，且层状纳米晶体（纳米片）和球形纳米晶体（纳米颗粒）共存。在此我们表明，通过使用油酸铅（Pb(CH₃COO)₂）作为唯一的铅源，并使用短链和长链混合烷基铵进行控制，可以实现CH₃NH₃PbBr纳米晶体的纯纳米颗粒形态。这些纳米晶体呈单分散状态（直径为2.2 ± 0.4纳米），具有高荧光性（量子产率接近85%），并且在溶液中高度稳定（超过30天）。对比研究表明，CH₃NH₃PbBr纳米晶体的形状强烈依赖于铅源PbBr₂和Pb(CH₃COO)₂，并随着前驱体中短链和长链烷基铵的比例而变化。在前驱体中短链与长链烷基铵的最佳比例为4∶6时，以Pb(CH₃COO)₂作为唯一铅源可以选择性地抑制CH₃NH₃PbBr纳米片的生长，提高所制备的CH₃NH₃PbBr纳米晶体的整体光致发光量子产率。这项工作为可控合成具有纯晶体形状、显著改善的光致发光性能和稳定性的钙钛矿纳米晶体揭示了重要的新见解。
