By combining the thermal evaporation and spin-coating techniques, we were able to demonstrate synthesis of 3 cm by 3 cm organometallic halide perovskite nanocrystalline thin film and to fabricate light-emitting diodes from this large-area film. Photophysical and electroluminescent properties of the devices were measured and characterized. The device showed a turn-on voltage of approximately 1.5 V with electroluminescence centered at 538 nm with a full width at half maximum of 22.8 nm. The device displays a high color purity, an external quantum efficiency, and a maximum luminance of 95％, ~1 ％, and 161cd/m2, respectively. Moreover, the large-area LEDs display long operation lifetime and shelf-life.Currently the area of perovskite LED components is still limited to a few mm square. Our team breaks this barrier by combine solution process with thermal evaporation to produce a large-area component with a size of 3 cm x 3 cm. The quality of the as-prepared perovskite film was carefully examined with various characterization techniques. For example, integrating sphere measurement proved that the LED has high color purity. Results from the photochromaticity measurements showed that the LED emission intensity was uniformity distributed from edge to edge. The proposed perovskite thin film synthesis process is simple, convenient, and low-cost. Moreover, it takes only 6 hours in average to fabricate large-area light emitting components without going through many complicated steps.Our perovskite LED manufacturing process is simple, less time-consuming and cost-effective. The demonstrated devices are large in area but very lightweight due to a thickness of only a few mm. A large number of perovskite LEDs can be made in a short period of time, which is favorable for mass production. Apart from the aforementioned advantages, these perovskite LEDs are uniformity in morphology with high color purity. Therefore, it can be used as a backlight for liquid crystal displays, or can be applied in monitors, TVs, automobiles, smart wearable devices, biomedical sensors, etc.. Moreover, the process is a two-step method, which has the characteristics of solution processing, therefore it is beneficial for developing flexible devices.