Blue light-emitting diodes (LEDs), as one of the three primary colors and an excitation light source, have important application requirements in full-color displays, general lighting, and signal transmission. In recent years, metal halide perovskites have become strong candidates for next-generation low-cost blue LEDs due to their high photoluminescence quantum yield, high color purity, and easy solution processability. To achieve high-performance blue perovskite LEDs, researchers have proposed various strategies, including material optimization, interface engineering, and device structure design. To date, the external quantum efficiency (PE) of blue perovskite LEDs has reached as high as 26.4%, but the power efficiency—a key indicator for evaluating LED power consumption—remains unsatisfactory.
Given the huge global energy footprint of LED technology and the inherently higher energy consumption of blue perovskites due to their wider bandgap compared to their red and green counterparts, improving the PE of blue perovskite LEDs is crucial for designing energy-efficient optoelectronic devices. The PE value is determined by the formula PE = (π × L)/(J × V), where L, J, and V represent luminance, current density, and driving voltage, respectively. Therefore, to achieve high PE (luminous emission distance), it is necessary to maximize brightness while reducing the driving voltage at a specific current density. Compared with LEDs based on perovskite polycrystalline thin films, quantum dot (QD) LEDs show promise for higher PE because the QD emitter itself possesses strong carrier confinement characteristics, enabling near-theoretical luminous efficiency. However, the electrical insulation properties of organic ligands in QDs severely hinder carrier transport and recombination, thereby increasing the driving voltage and resulting in relatively low PE for these devices.
Song Jizhong, Yao Jisong, and others from Zhengzhou University were able to reduce the driving voltage and enhance radiative recombination of blue perovskite QLEDs by inserting ordered dipole structures of poly(1,1-difluoroethylene) into the QD emitting layer. The polymer dipoles formed by PVDF can guide electrons and holes into the central region of the emitting layer for radiative recombination, which helps to reduce the device's driving voltage. Simultaneously, the electron-withdrawing effect of F atoms on PVDF can effectively passivate uncoordinated Pb²⁺, while the corresponding H atoms can interact with halide ions in the perovskite QDs, effectively suppressing non-radiative recombination. As a result, a record-breaking power efficiency of 43.9 lm W⁻¹ was successfully achieved in blue perovskite QLEDs, along with an impressive brightness of 5474 cd m⁻². Furthermore, the optimized devices exhibited stable emission spectra and significantly improved operational stability, demonstrating the great potential of the proposed blue perovskite QLED strategy in practical applications.
