Multiple Cations Enhanced Defect Passivation of Blue Perovskite Quantum Dots Enabling Efficient Light‐Emitting Diodes

Abstract

All inorganic perovskite quantum dots (ABX3, A = Cs, B = Pb, X = Cl, Br, or I) are potential candidates for wide‐color‐gamut display applications. High‐efficiency green and red perovskite quantum dot (PeQD) light‐emitting diodes (LEDs) have been achieved, however, development of blue‐emitting devices, especially those with the relatively short wavelengths (<470 nm) meeting National Television System Committee blue standard, lag largely behind, mainly due to poor film quality, low photoluminescence quantum yield (PLQY) of PeQDs, and unfavorable device structure. Here, a strategy of co‐doping Rb+ and Ni2+ in (Cs0.8Rb0.2)(Pb0.95Ni0.05)(Br1.8Cl1.2) PeQDs is reported to improve the film quality and PLQY of PeQDs by realizing multiple passivations and modifying the energy band of PeQDs to reduce the hole injection barrier. With further engineering the device structure to facilitate the hole transport, PeQDLEDs based on multiple‐cation PeQDs show the maximum EQE of 2.14% and the emission peak at 467 nm with a full width at half maximum of 16 nm. This work would open up a new avenue to design and develop efficient blue‐emitting materials for high‐performance blue PeQDLEDs.

Recent Advances in Blue Perovskite Quantum Dots for Light‐Emitting Diodes

“…[120] Previous reports revealed that the multiple A-cation strategy was more efficient to inhibit halide segregation. [23,[121][122][123] For example, the (Cs/ Rb/FA/PEA/K)Pb(Cl/Br) 3 blue PeLEDs demonstrated high half-lifetime over 300 min without spectral shift. [23] Moreover, Zhang et al designed a hydrogen-bonded amine-group doping strategy for color-stable blue PeLEDs.…”

“…Interestingly, the analogous divalent ions such as Ni 2+ and Nd 2+ ions have similar impacts on mixed-halide PQDs, which could also be incorporated into the lattice to boost PL QY and enhance stability. [102,122,157,158] The blue emission can be tailored by not only mixing halides and quantum confinement effect, but also doping metal ions into all-bromide PQDs. Figure 8e-g show tunable blue emission of CsPbBr 3 PQDs by the substitution of Pb 2+ with isovalent cations (Sn 2+ , Cd 2+ , and Zn 2+ ), [138] where the blue shift of the absorption and PL spectra was observed in all cases.…”

“…Doping metal ions into the blue PQDs contributes to the optimization of PeLEDs performance. [121,149,156,183] Multiple cations incorporation, such as Rb + /FA + , [145] Rb + /Ni 2+ , [122] is beneficial to increase exciton binding energy and prepare highquality PQDs film, which can be used to realize high EQE for blue devices. Similarly, a rational mount of K + ions facilitates improving the surface morphology of CsPbBr x Cl 3−x PQDs film, which promotes the device efficiency with a champion EQE of 1.96% and a maximum luminance of 86.95 cd m −2 at 477 nm.…”

Perovskite Light‐Emitting Electrochemical Cells Employing Electron Injection/Transport Layers of Ionic Transition Metal Complexes

“…Furthermore, carrier injection/ transport engineering of perovskite LEDs has also been confirmed to be effective in improving device efficiency. [58,59] As such, the multilayer perovskite LEC/LED structure can take advantages of both LECs and LEDs. [60] Similar to perovskite LEDs, optimizing the carrier balance of perovskite LEC/LEDs can be realized by adjusting injection/transport layer thickness.…”

Preparation and Research of Perovskite Quantum Dots Powder Based on RbCl Doped CsPbBr3

“…As one of the three primary colors, blue emission is a necessary condition to achieve high quality display and white light illumination [17] . Among the three primary color quantum dots (QDs), the performance of blue light devices is the worst, whether made into quantum dots or thin film devices [18] . To effectively regulate the photoelectric properties of nanocrystals, applying doping to the target semiconductor lattice is the most effective way to adjust the properties of semiconductor materials without changing the host crystal structure and basic properties [19–21] .…”