Surfactant effects have been one of the most important surface techniques to tunesurface properties and growth mode.Based on our first principles studies,we recently discoverednovel effects of Sb enhanced In incorporation in InGaN and Surfactant K tuned ZnS secondaryphase in CZTS.These discoveries are expected to largely enhance the device performance ofgreen LED and CZTS based solar cells.This work was supported by the start-up fund and directgrant with the Project code of 4053134 at CUHK.