2, Hongik University, Sejong, , Korea (the Republic of)
Utilizing the decay-to-recovery emission characteristics of unstable quantum dots (QD) under light exposure, a non-physical photopatterning method is developed. Due to the intrinsic nature of the evolution, several patterns based on polymer-QD composites, including a unique negative-to-positive pattern transformation with high contrast are possible. Furthermore, the transformation can be programmed to yield bright/dark region switch with the help of well-controlled exposure. The fabrication of a large scale (mm2) QD-polymer photopattern is a fast parallel process, as the transformation occurs within seconds. In addition, the photoluminescence of faded photopatterns (after sitting in ambient for a period of time) can be partially restored by light exposure. This flexible patterning method may find its application in light sensors, anti-counterfeiting labels and patterns where contrast should be realized without physical patterning.