Perovskites for hybrid light emitting devices
Nowadays, light-emitting diodes (LEDs) have been used in various areas, such as illumination, signals, automotive, mobile appliances, decoration, and so on. Many materials have been used for the LEDs. Perovskites, as a new type of luminescent materials, are attracting more and more attention of both academia and industry communities. This is due to their narrow spectral bandwidth, high photoluminescence quantum yields (PLQY) as well as the versatility in changing their composition and shape. For instance, the emission can be easily tuned from blue to deep red through the compositional engineering or changing the size of these particles. However, the stability and the significant non-radiative recombination are still big concerns for the optoelectronic use of perovskites. In this work, several strategies have been put forward to achieve efficient and stable perovskite based-LEDs.
Firstly, CsPbBr3 core was incorporated into the ZrO2/SiO2 shell through the hot injection and the subsequent hydrolytic process. The obtained perovskite shows narrow emission and a high PLQY of ca. 65%. In addition, the perovskite nanocrystal based-device has excellent thermal and operation stability, the lifetime of the LED device is about 680 h under a constant current of 10 mA. Besides, the device also has a high energy conversion and shows a maximal luminous efficacy of about 70.21 lm/W at 20 mA.
Secondly, we synthesized the quasi-2D (BA)2(MA)n-1PbnBr3n+1 through incorporating the big spacer BA group to the 3D MAPbBr3 structure. The PLQYs of these films are highly improved after introducing the ion conductive polymer poly(ethylene oxide) (PEO) into the perovskite precursors. Multiple excitonic absorption features at 401 nm, 434 nm, 450 nm are observed for the (BA)2(MA)n-1PbnBr3n+1 layers, indicating the successful fabrication of the quasi-2D structure. We also configured LED with the structure ITO/PEDOT:PSS (35 nm)/perovskite (60 nm)/TPBi (40 nm)/Al (100 nm). High brightness and low turn-on voltage of about 4.5 V are obtained for the LEDs.