ECCS-EPSRC Superlattice Architectures for Efficient and Stable Perovskite LEDs

卤化铅钙钛矿在太阳能电池中显示出真正的应用前景，但在LED中也非常有希望，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设计的设备架构的LED操作，并能够将量子效率提高到高值(接近100%的内部量子效率)。然而，这些设备需要比最佳驱动电压更高的电压，从而限制电源效率和工作寿命。在这个项目中，我们将实现新的钙钛矿型LED结构，在与显示相关的条件下，提供功率效率和稳定性的阶梯变化。我们认为，通过选择2D和3D钙钛矿型结构，建立全钙钛矿型异质结构半导体堆栈，实现局部带隙控制是一个真正的机会。我们将开发和展示新的薄膜钙钛矿型LED架构，这种架构使用可控工程的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量子井技术。我们将开发一层又一层的钙钛矿结构的沉积，包括低带隙3D层和大间隙2D层的堆叠。这将被设计成在中心2D/3D超晶格中引起电荷复合，以及将电子和空穴传输到两侧的2D钙钛矿层，从而将电荷复合区限制在远离异质界面上的猝灭位置的两侧。电子和空穴的选择性注入将由有机电荷传输材料提供。它们将通过化学调节和掺杂(确保与掺杂相关的陷阱/猝灭状态与发射钙钛矿区域足够远)在钙钛矿界面上进行欧姆注入，并在两个电极上进行欧姆接触。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APbBr3材料显示出接近理想的绿色CIE坐标，并在项目的后半部分将我们的设计扩展到红色和蓝色钙钛矿发射体。我们将重点测试隔离发射材料和LED，利用我们为同类最佳的钙钛矿型太阳能电池建立的协议，但这里为发光量身定做。该项目的目标将是开发生长钙钛矿型超晶格结构的工艺方法，将其实施在高能效LED中，并展示通过在低驱动电压下运行实现的增强的操作稳定性。我们的目标是在与显示相关的条件下逐步改变功率效率和稳定性。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，探索行业影响的潜力。

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.