利用溶液加工的界面阻挡层实现高效三维和准二维金属卤化物钙钛矿发光二极管

Efficient 3D and quasi-2D metal halide perovskite light-emitting diodes by a solution processed interface barrier layer

为了保护金属卤化物钙钛矿发光层免受强酸性聚合物(poly-(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid),PEDOT:PSS)的腐蚀,一种具有空穴传输能力的有机小分子材料(N,N-dicarbazolyl-3,5-benzene, mCP)被当作界面阻挡层引入三维钙钛矿发光层(CsPbBr_(3))和PEDOT:PSS之间。研究表明,mCP不仅可以从空间上隔离CsPbBr_(3)和PEDOT:PSS,抑制PEDOT:PSS对CsPbBr_(3)发光层的降解,还可以使钙钛矿薄膜的覆盖率更高,颗粒更小,提高薄膜质量,减少薄膜缺陷对激子的淬灭。同时,mCP的引入可以提高空穴注入和传输能力,使得相同电压下形成的激子更多;由于mCP具有比PEDOT:PSS更高的最低电子不占有态和更大的能隙,能更好地将激子限制在发光层中,进一步提高激子的发光辐射复合和器件的电致发光效率。与原始不加mCP的器件相比,基于mCP的3D CsPbBr_(3)钙钛矿发光二极管(Perovskite light-emitting diode, PeLED)的电致发光性能得到了显著提升,获得了4.86 cd/A最大电流效率。接着,这种方法在基于PEA_(2)Cs_(n-1)Pb_(n)Br_(3n+1)的准二维PeLED中也被证实是可行的,器件的最大电流效率被提升到24.79 cd/A。

An organic small molecular material(N,N-dicarbazolyl-3,5-benzene, mCP) with hole transporting ability was introduced as an interfacial barrier layer between the metal halide perovskite luminescent layer(CsPbBr_(3)) and the strongly acidic polymer poly-(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid)(PEDOT:PSS) to protect CsPbBr_(3) from corrosion. The study showed that mCP not only can spatially isolate CsPbBr_(3) and PEDOT:PSS to inhibit the degradation of PEDOT:PSS on the CsPbBr_(3) luminescent layer, but also can improve the film quality, making the coverage of the perovskite film higher and the grains smaller, and thus reducing the quenching defect. At the same time, the introduction of mCP can improve the hole injection and transport ability, resulting in more excitons generated under the same voltage. Since mCP has a higher lowest electron unoccupied state and a larger energy gap than PEDOT:PSS, which can confine excitons better in the luminescent layer, improving the radiation recombination of excitons, thereby improving the electroluminescence efficiency of the device further. Compared with the reference device without mCP, the electroluminescence performance of the 3D CsPbBr_(3) perovskite light-emitting diode(PeLED) based on mCP was significantly improved, achieving a maximum current efficiency of 4.86 cd/A. Subsequently, this method was also proven to be feasible in quasi-two-dimensional PeLEDs based on PEA_(2)Cs_(n-1)Pb_(n)Br_(3n+1), exhibiting the maximum current efficiency of 24.79 cd/A.