ECCS-EPSRC Superlattice Architectures for Efficient and Stable Perovskite LEDs

卤化铅钙钛矿显示出用于太阳能电池的真实的前景，但也非常有希望用于LED，因为它们可以在薄膜结构中显示出高的发光量子产率。研究人员首先展示了使用基于有机LED设计的器件架构的LED操作，并且能够将量子效率提升到高值（接近100%的内部量子效率）。然而，这些器件需要比最佳驱动电压更高的驱动电压，这限制了功率效率并限制了操作寿命。在这个项目中，我们将实现新的钙钛矿LED架构，在显示相关条件下提供功率效率和稳定性的阶跃变化。我们认为有一个真实的机会来构建全钙钛矿异质结构半导体堆叠，通过选择2D和3D钙钛矿结构来实现局部带隙控制。我们将开发和展示新的薄膜钙钛矿LED架构，该架构使用可控设计的2D/3D“超晶格”钙钛矿结构作为发射层和电荷传输层-灵感来自商业GaN量子阱技术。我们将开发钙钛矿结构的逐层沉积，该结构包含具有较大间隙2D层的较低带隙3D层的堆叠。这些将被设计为在中心2D/3D超晶格中引起电荷复合，以及在两侧的电子和空穴传输2D钙钛矿层，其将电荷复合区限制在远离两侧异质界面处的淬灭位点。电子和空穴向这些结构的选择性注入将由有机电荷传输材料提供。这些将被设计为通过化学调谐和掺杂（确保与掺杂相关的陷阱/淬灭状态离发射钙钛矿区足够远）在钙钛矿界面处提供欧姆注入，并被设计为在两个电极处提供欧姆接触。该项目需要在一系列材料化学，材料加工和半导体工程任务方面取得进展，并以先进的表征技术为基础。我们将首先开发绿色LED，因为APbBr 3材料显示出接近理想的绿色CIE坐标，并在项目的下半年将我们的设计扩展到红色和蓝色钙钛矿发射器。我们将对隔离发射材料和LED进行压力测试，利用我们为同类最佳钙钛矿太阳能电池制定的协议，但在此为光发射量身定制。该项目的目标是开发钙钛矿超晶格结构生长的处理方法，将其应用于节能LED，并通过低驱动电压操作实现增强的操作稳定性。我们的目标是在显示相关条件下实现功率效率和稳定性的阶跃变化。除了通过出版物和会议传播的学术影响外，我们还将在我们已经建立的基本专利组合的基础上探索工业影响的潜力。

Lead halide perovskites show real promise for use in solar cells, but are also very promising for use in LEDs, since they can show high luminescence quantum yields in thin film structures. The investigators were first to show LED operation using device architectures based off designs for organic LEDs and were able to lift quantum efficiencies to high values (close to 100% internal quantum efficiency). However, these devices require higher than optimum drive voltages that limit power efficiency and limit operational lifetime. In this project we will realise new perovskite LED architectures that deliver a step change in power efficiency and stability at display-relevant conditions.We consider there is a real opportunity to build all-perovskite heterostructure semiconductor stacks that achieve local bandgap control through choice of 2D and 3D perovskite structures. We will develop and demonstrate new thin-film perovskite LED architectures that use controllably engineered 2D/3D 'superlattice' perovskite structures as the emissive layers and as charge transport layers -- inspired by commercial GaN quantum well technologies. We will develop layer by layer deposition of perovskite structures containing stacks of lower-bandgap 3D layers with larger gap 2D layers. These will be designed to cause charge recombination in a central 2D/3D superlattice, together with electron- and hole-transporting 2D perovskite layers to either side that confine the charge recombination zone away from quenching sites at the heterointerfaces to either side. Selective injection of electrons and holes to these structures will be provided by organic charge transport materials. These will be engineered to give ohmic injection at the perovskite interfaces, through chemical tuning and doping (ensuring that trap/quenching states associated with doping are far enough away from the emissive perovskite zone) and designed to give ohmic contacts at the two electrodes. This project requires advances across a range of materials chemistry, materials processing and semiconductor engineering tasks, underpinned by advanced characterisation techniques. We will initially develop green LEDs, since the APbBr3 materials show close to ideal green CIE coordinates, and extend our designs to red and blue perovskite emitters in the second half of the project. We will stress-test isolated emission materials and LEDs, leveraging protocols we have established for the best-in-class perovskite solar cells but tailored here for light emission.The objectives for the project will be the development of processing methodologies for growth of perovskite superlattice structures, their implementation in power-efficient LEDs, and the demonstration of enhanced operational stability, achieved through operation at low drive voltages. We target a step change in power efficiency and stability at display-relevant conditions. Besides academic impact, disseminated through publications and conferences, we will explore potential for industrial impact, building on the fundamental patent portfolio we have been establishing.