Based upon Coherent Förster Resonance Energy Transfer, we have successfully demonstrated the first colloid quantum dot laser with two different kinds of quantum dots (donorsacceptors) in the light emitting layer. The donors can resonantly transfer energy into the acceptors,they also act as scattering centers. Through multiple scattering, it can form a coherent closed loop. All the donors can coherentlyresonantly transfer energy into all the acceptorsthe laser action is achieved.

By combining the thermal evaporation and spin-coating techniques, we are able to demonstrate synthesis of 3 cm x 3 cm and 1.5 cm x 1.5 cm organometallic halide perovskite light-emitting diodes with electroluminescence at 538 nm and 405 nm, respectively. Other than the advantage in large device area, to our best knowledge, the demonstrated violet LEDs have produced the shortest emission wavelength available from current hybrid perovskites. The luminance of our green LEDs reach a maximum value of 9967 cd/m2 with an EQE of 0.88% and color purity of 95%. Moreover, it is possible to generate white light emission by combining the violet perovskite LEDs with visible light phosphor.