to their transparency, solution processability, broad absorption, high quantum yield (QY), tunable bandgap, and sharp emission spectrum. [5][6][7][8][9] In recent years, the development of flexible lighting/display devices has required the integration of luminescence materials on flexible substrates with the characteristics of luminescence properties and the capability to be stretched into arbitrary shapes.A possible approach for this purpose is to incorporate QDs into a transparent composite film, in which the polymer matrix provides mechanical stretchability and chemical stabilization for the nanosized particles. [10][11][12] Unfortunately, assembling QDs into solid films from solvents generally results in agglomeration and complexation with polymer molecules, dramatically deteriorating the photoluminescence quantum yield (PLQY) due to nonradiative processes. The PL intensity of QDs embedded in a polymer matrix is acknowledged to be several times lower than that of colloidal QDs. [13][14][15] Moreover, the weakening of the out-coupling efficiency by the high refractive index polymer matrix further reduces the PL emission from the film. [16][17][18] These inherent drawbacks limit the development of QDs used in flexible devices for practical applications. TheThe development of quantum dot (QD) composite films for lighting and displays is of great importance because of their exceptional mechanical flexibility, chemical stability, and optical tunability. Generally, QDs are attached to plasmonic nanostructures to enhance their photoluminescence (PL) emission. However, plasmonic QD composite films suffer from deteriorated inherent quantum yields and lower enhancement ratios due to variations in the refractive index and dielectricity in the composites. Herein, the use of a dielectric microsphere cavity is reported to realize over 1000-fold enhancement of the PL in CdSe/ZnS QD/polydimethylsiloxane films with a highly unidirectional emission angle of ≈9°. The field regulation by the optical whispering-gallery resonance and directional antenna effect at the microscale is revealed to interpret the PL enhancement mechanism. Additionally, the microsphere cavity allows for the enhancement of white-light emission in the RGB-QD hybrid composite film. The present work inspires a straightforward strategy for boosting the light efficiency in QD composite films, with promising applications in flexible lighting/display devices.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.