. Optimization strategies for luminescence performance and stability of LED devices

. Schematic diagram of the device structures (a, b) and working mechanism (c) for perovskite based planar heterojunction LEDs

. (a) Schematic diagram of device structure; (b) Cross-sectional TEM image. Scale bar, 50 nm; (c) Flat-band energy level diagram; (d) The EL spectra (straight line) of devices for CsPb(Cl/Br)₃, CsPbBr₃ and CsPb(Br/I)₃ under applied voltage of 5.5 V, and the photoluminescence (PL) spectra (dashed line) of QDs dispersed in hexane^[58]

. (a) Schematic illustration of device structure and a cross-sectional TEM image (scale bar: 50 nm); (b) Normalized EL spectra (solid lines) and PL spectra (dashed lines) of CsPbBr₃ QLEDs with two purifying cycles. Inset in (b): The photograph of a working device at an applied voltage of 5 V; (c) EQE of these devices for QDs with different purifying cycles as a function of luminance^[59]

. (a) Structural representation of CsPbBr₃ based LEDs; (b) Current efficiency-voltage (CE-V), and EQE-voltage (EQE-V) characteristic curves^[68]; The surface morphology of CsPbBr₃ film and surface luminous photo of LED (c) without treatment and (d) with chlorobenzene treatment^[69]

. (a) EQE and CE as a function of voltage among devices fabricated with different ETL and HTL materials^[77]; (b) EQE-V curves for the LEDs with different PEG:CsPbBr₃ (CsBr:PbBr₂ molar ratio of 1.4:1) weight ratios^[78]; (c) TEM image of cross section of device and corresponding schematic diagram of device structure; (d) EQE for the devices with and without Ag rod^[79]

. (a) Overall energy band diagram of the LED structure; (b) EQE and CE vs current density of devices with or without PFI interface modifier^[85]; (c) Schematic diagram of device structure; (d) CE and EQE of devices with and without PVP buffer layer, with and without CH₃NH₃Br (MABr) additive^[51]

. (a) Schematic illustration of device structure; (b) EQE of the devices as a function of luminance^[90]; (c) Band alignment of each functional layer; (d) EQE of the devices as a function of driving voltage^[91]

. (a) Simplified energy band alignment of the LED; (b) Luminous efficiency and EQE versus voltage of the LED^[99]; (c) Schematic illustration of solution-processed perovskite LED; (d) EQE, CE, and power efficiency versus voltage of the LED^[102]