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Abstract:

LED light bulbs that simulate solar spectrum were fabricated using CdSe core-shell quantum dots in combination with GaN blue-light chips. They exhibited excellent optical properties such as white CIE coordinates of (0.33, 0.33), high color rendering index (CRI) of 98 and correlated color temperature (CCT) of 5352 K. Moreover, a circuit system was used to control the LEDs so that the lighting spectrum changes with the time in a day to simulate the actual solar spectrum. The results show that the sun-like spectrum smart bulbs not only have good optical properties and high electrical stability, but also can automatically adjust their spectrum according to the time, making the lighting natural. This work makes sun-like lighting conditions for some special environments to promote the application of smart bulbs in smart lighting.

Abstract:

2D transition metal carbides, nitrides, and carbonitrides called MXenes show outstanding performance in many applications due to their superior physical and chemical properties. Herein, a ZnO-MXene mixture with different contents of Ti₃ C₂ is applied as electron transport layers (ETLs) and the influence of the Ti₃ C₂ MXene in all-inorganic metal halide perovskite nanocrystal light-emitting diodes (perovskite NC LEDs) is explored. The addition of Ti₃ C₂ makes more balanced charge carrier transport in LEDs by changing the energy level structure and electron mobility of ETL. Moreover, lower surface roughness is obtained for the ETL, thus guaranteeing uniform distribution of the perovskite NCs layer and further reducing leakage current. As a result, a 17.4% external quantum efficiency (EQE) with low efficiency roll-off is achieved with 10% Ti₃ C₂ , which is a 22.5% improvement compared to LEDs without Ti₃ C₂ .

Abstract:

Perovskite nanocrystal light-emitting devices (PNC LEDs) exhibit great potential in display and lighting applications. Balanced hole and electron injection in the light-emitting layer is undoubtedly an effective way to improve LED performance. Here, bismuth (Bi) was introduced into PNC LEDs to form a silver-bismuth (Ag-Bi) bilayer anode. Ag diffused into a defective 2 nm thick Bi layer to form an alloy-like state that promoted hole injection, reduced the charge transfer resistance, and enhanced charge transfer, leading to more balanced hole-electron carriers in the emission layer through hole injection enhancement. As a result, the turn-on voltage and brightness changed from 2.41 V and 2200 cd m^-2, respectively, for CsPb_1-xZn_xI₃-based LEDs with a Ag monolayer anode to 2.2 V and 3714 cd m^-2, respectively, for devices with a Ag-Bi bilayer anode. In addition, the performance of CsPbI₃ and CsPbBrI₂ PNC-based LEDs has also been effectively improved by using a Ag-Bi bilayer anode.

Abstract:

Perovskite white light-emitting devices (WLEDs) without intercalation layers have not been achieved due to the ion exchange. Although the intercalation layers prevent ion exchange between perovskite nanocrystals (NCs), it also creates a new problem of charge imbalance and the structure becomes more complex. In this study, blue emitting ZnCdS/ZnS NCs with high quantum yield and stability are introduced to work with the yellow emission from CsPb(Br/I)₃ perovskite NCs for WLEDs. The WLEDs are constituted of ITO/ZnO/PEI/ZnCdS/ZnS NCs/CsPb(Br/I)₃ NCs/TCTA/MoO₃/Au. This design avoids ion exchange between different perovskites NCs, and realizes white light emission by simple fabrication. As a result, we achieved the white light coordinates of (0.34, 0.34) and a correlated color temperature of 5153 K.

Abstract:

All-inorganic cesium lead halide perovskite nanocrystals (NCs) have demonstrated excellent optical properties and an encouraging potential for optoelectronic applications; however, mixed-halide perovskites, especially CsPb(Cl/Br)₃ NCs, still show lower photoluminescence quantum yields (PL QY) than the corresponding single-halide materials. Herein, anhydrous oxalic acid is used to post-treat CsPb(Cl/Br)₃ NCs in order to initially remove surface defects and halide vacancies, and thus, to improve their PL QY from 11% to 89% for the emission of 451 nm. Furthermore, due to the continuous chelating reaction with the oxalate ion, chloride anions from the mixed-halide CsPb(Cl/Br)₃ perovskite NCs could be extracted, and green emitting CsPbBr₃ NCs with PL QY of 85% at 511 nm emission are obtained. Besides being useful to improve the emission of CsPb(Cl/Br)₃ NCs, the oxalic acid treatment strategy introduced here provides a further tool to adjust the distribution of halide anions in mixed-halide perovskites without using any halide additives.