Simplifying　device　structure　for　improving　performance　stability　of　colloidal　quantum　dots-based　light　emitting　devices　(QD-LEDs)　is　of　importance　for　advanced　photoelectric　application.　In　this　work,　a　QD-LED　with　ultrasimple　structure　is　demonstrated,　which　is　working　in　single-terminal-injection　mode　driven　under　alternating　current　field.　The　QD-LEDs　are　only　composed　of　electrodes,　insulator,　and　QD　layer　without　any　other　organic　functional　layers,　forming　an　ultra-thin　structure　of　indium　tin　oxide　(ITO)/Al2O3/QDs/Ag.　The　effect　of　the　Al2O3　thickness　on　the　device　performance　is　discussed.　Different　from　conventional　devices,　the　QD-LEDs　show　high　stability,　which　can　work　stably　in　air　without　any　further　sealing　treatment　and　can　work　normally　in　the　wide　temperature　range　from　-190　degrees　C　to　100　degrees　C　without　obvious　degration.　Finally,　the　working　mechanism　related　to　the　electron　accumulation　and　interface-capture　is　proposed.　We　believe　this　work　can　extend　the　working　mechanism　model　of　QD-LEDs,　provide　guidance　for　improving　QD-LEDs,　and　provide　methods　for　obtaining　advanced　QD-based　light-emitting　technology.