Rational Control of Size and Photoluminescence of WS Quantum Dots for White Light-Emitting Diodes.

Transition-metal dichalcogenides like tungsten disulfide (WS) are luminescent but still bear low quantum yields and hardly meet the requirement of practical applications. Here, we developed a hot-injection method to prepare highly luminescent WS quantum dots with tunable particle size in a noncoordinating solvent, some that are even smaller than its Bohr radius. The as-synthesized WS quantum dots exhibit a narrow size distribution and a high photoluminescence quantum yield of 32%, the highest record compared to the known reports. The WS quantum dot layer was employed to fabricate white light-emitting diodes with a maximum brightness of 507 cd/m, adjustable color temperatures from 4100 to 10 000 K, and excellent color rendering index of 91. These results confirm the promising optoelectronic applications of WS quantum dots.