Tailoring Phase Distribution of Quasi-2D Perovskites via Taurine-Assistance Enables Efficient Blue Light-Emitting Diodes.

Quasi-2D (Q-2D) perovskites with typical varied n-phase structures deserve promising candidates in pursuing high-performance perovskite light-emitting diodes (PeLEDs). Whereas their weakness in precise n-phase distribution control disables the optical property of PeLEDs since the n = 1 phase is dominated by severe nonradiative recombination. Here, an effective phase distribution tailoring strategy is developed for pure blue PeLEDs by introducing taurine (TAU) into mixed halide Q-2D perovskites. The sulfonic acid group in TAU can coordinate with Pb2+ to suppress the formation of the n = 1 phase while promoting the growth of Q-2D perovskites into domains with the graded distribution of n = 2 and 3. The amino group in TAU forms hydrogen bonds with electronegative halide ions, suppressing the formation of halide vacancies and reducing the defect density in the Q-2D perovskite films. As a result, optimized blue Q-2D perovskite films boosted PLQY to 92%. Target blue PeLED  was endowed with a peak EQE of 14.82% (average 12.6%) at 475 nm and a maximum luminance of 1937 cd m-2 , which is among the reported high-level pure blue PeLEDs. This work demonstrates a feasible approach to regulate the phase distribution of Q-2D perovskites for high-performance blue PeLEDs.

Tunable White Light-Emitting Devices Based on Unilaminar High-Efficiency Zn2+-Doped Blue CsPbBr3 Quantum Dots.

Perovskite-based white-light-emitting devices (WLEDs) are expected to be the potential candidate for the next-generation lighting field due to their scalability and low-cost process. However, simple and adjustable WLED fabrication technology is in urgent need. Here, WLEDs with a single layer of perovskite quantum dots (PQDs) were constructed by combining Zn2+-doped CsPbBr3 PQDs with exciplex emission between poly(9-vinylcarbazole) (PVK) and ((1-phenyl-1H-benzimidazol-2-yl)benzene)) (TPBi). Zn2+-doped CsPbBr3 PQDs with polar ion shells were prepared by means of low temperature and post-treatment. The photoluminescence quantum yield (PLQY) can reach as high as 95.9% at the emission wavelength of 456 nm. The blue shift of its PL (∼60 nm) is much greater than that of other reported Zn2+-doped CsPbBr3 PQDs (5-10 nm), thus realizing the true blue-emission Zn2+-doped CsPbBr3 PQDs. As a result, just by controlling the thickness of TPBi, the adjustment of cold (CIE (0.2531, 0.2502)) and warm WLEDs (CIE (0.3561, 0.3562)) is realized for the first time.