Zhengzhou University researchers have developed a dipole-engineering strategy that significantly improves the power efficiency of blue perovskite quantum dot LEDs, addressing a long-standing bottleneck in the field.
Blue perovskite LEDs are critical for applications such as full-color displays, general lighting, and optical signal transmission, but their power efficiency (PE) has lagged behind despite external quantum efficiencies (EQEs) exceeding 25%. This limitation is mainly due to the wider bandgap of blue emitters, which requires higher driving voltages, as well as insulating organic ligands on quantum dot (QD) surfaces that hinder carrier transport and increase energy consumption.
To overcome these challenges, the researchers incorporated an ordered dipolar polymer, poly(1,1-difluoroethylene) (PVDF), into the CsPbCl3−xBrx QD emitting layer. The dipolar structure of PVDF plays a dual role in regulating charge dynamics and suppressing nonradiative losses.
The polymer dipoles guide electrons and holes toward the central region of the emitting layer, promoting efficient radiative recombination and improving carrier balance. This dipole-assisted charge regulation reduces the driving voltage required for device operation, enabling a low turn-on voltage of 2.2 V.
At the same time, the polar nature of PVDF enables effective surface defect passivation. The electron-withdrawing fluorine atoms interact with uncoordinated Pb²⁺ ions, while hydrogen atoms interact with halide ions (Br⁻/Cl⁻) on the QD surface. These interactions suppress trap-assisted nonradiative recombination, leading to reduced energy losses and improved photoluminescence efficiency.
As a result of this combined mechanism, the optimized blue (486 nm) perovskite QLEDs achieve a record power efficiency of 43.91 mW−1, alongside an EQE of 28.7%, a maximum luminance of 5474 cd m−2, and stable spectral output. The devices also demonstrate improved operational stability under continuous operation.
In addition, the PVDF-modified QD films exhibit high photoluminescence efficiency and reduced surface roughness, further contributing to improved device performance. By simultaneously enhancing charge transport, recombination efficiency, and defect passivation, this dipole interface engineering strategy effectively resolves the efficiency mismatch between EQE and PE in blue perovskite LEDs, providing a promising pathway toward energy-efficient perovskite optoelectronic devices.
