Optimizing charge balance in carbon dot-based LEDs for enhanced performance

It is challenging to pursue brighter and more efficient light-emitting diodes (LEDs) based on carbon dot (CD) emitting layers. In this study, we present a novel approach to successfully push the boundaries of CD-based LEDs forward remarkably. Firstly, by utilizing a modified method, we successfully synthesized CDs. Then the charge balance of this device was effectively optimized by blending the renowned hole transport material, 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP) with CDs as an emitting layer. The fusion of these materials resulted in hybrid CDs exhibiting a pronounced P-type conductivity, leading to a significant surge in hole carrier density. This enhancement in conductivity is pivotal as it amplifies the efficiency of hole injection, a critical factor in LED brightness. To further refine our design, we doped a ZnMgO electron transport layer with polyvinyl pyrrolidone, achieving a meticulous moderation in the carrier transport rate. This intricate balance ensures optimal interaction between hole and electron injections. As a result of our comprehensive research and innovative interventions, the optimized LED device radiated with an extraordinary brightness of 505 cd m−2, combined with a low turn-on voltage of 2.5 eV. This development undeniably marks a significant milestone in the evolution of all solution CD devices.