Alternative Type 2D-3D Lead Halide Perovskite with Inorganic Sodium Ions as Spacer for High Performance Light Emitting Diodes
Chen Wu ‡1 , Tian Wu ‡1 , Yingguo Yang 2 , John A. McLeod 1 , Yusheng Wang 1 , Yatao Zou 1 , Tianshu Zhai 1 , Junnan Li 1 , Muyang Ban 1 , Tao Song* 1 , Xingyu Gao 2 , Steffen Duhm 1 , Henning Sirringhaus* 3 and Baoquan Sun* 1
1 Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Soft Materials (FUNSOM), Joint International Research Laboratory of Carbon-Based Functional Materials and Devices, Soochow University, 199 Ren’ai Road, Suzhou 215123, People’s Republic of China
2 Shanghai Synchrotron Radiation Facility (SSRF), Shanghai Institute of Applied Physics, Chinese Academy of Sciences, 239 Zhangheng Road, Pudong New Area, Shanghai 201204, China
3 Cavendish Laboratory, Department of Physics, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, UK
Two-dimensional (2D) lead halide perovskites with long-chain ammonium halides display high photoluminescence quantum yield (PLQY), due to their size and dielectric confinement, which promise a high efficiency and low-cost light emitting diode (LED). However, the presence of insulating organic long-chain spacer cation (L) dramatically deteriorates the charge transport properties along the out-of-plane nanoplatelet direction or adjacent nanocrystals, which would limit the LED device performance. In order to overcome this issue, we successfully incorporate small alkaline ions such as sodium (Na+) to replace long organic molecule. Grazing incident X-ray diffraction (GIXRD) measurements verify the 2D layered formation with preferential crystallite orientation. In addition, the incorporated sodium salt also generates amorphous sodium lead bromide (NaPbBr3) in perovskite as spacers to form nanocrystal-like halide perovskite film. PLQY is dramatically improved in the sodium incorporated film associating with enhanced PL lifetime. With incorporating small concentration of an organic additive, this 2D-3D perovskite can achieve a compact and uniform film. Therefore, a 2D-3D perovskite achieves a high external quantum efficiency (EQE) of 15.9% with good operational stability. Our work develops a type of 2D-3D halide perovskite with various inorganic ions as spacers for high performance of promising optoelectronic devices.