Core/Alloyed-Shell Quantum Dot Robust Solid Films with High Optical Gains

We report high optical gain from freestanding, optically stable, and mechanically robust films that are loaded with cross-linked CdSe/Cd_1-xZn_xSe_1-yS_y core/alloyed shell quantum dots (QD). These solid films display very high net optical gain as high as 650 cm^-1 combined with a low pump excitation gain threshold of 44 μJ/cm². The functionalization of the QDs using short-chain bifunctional cross-linkers not only significantly improves the net optical gain by allowing for a nearly 2-fold increase in QD loading but also provides stable passivation of the QDs which imparts excellent thermal stability, mechanical robustness, and stability under harsh chemical environments. The gain achieved here is up to 3-fold higher than that typically reported for traditional drop-cast QD films. Moreover, stable photoluminescence over long shelf storage time is a distinguished characteristic of the films. The QD films fabricated here span large areas (several cm²), can be readily micropatterned and sustain multiple harsh chemical treatment. Furthermore, they can be readily transferred onto different substrates without compromising their structural integrity and without diminishing optical activity that opens the paths to design complex and robust gain-loss optical structures.