Cu2+-Doped CsPbI3 Nanocrystals with Enhanced Stability for Light-Emitting Diodes.
18 Mar 2021-Journal of Physical Chemistry Letters (American Chemical Society)-Vol. 12, Iss: 12, pp 3038-3045
TL;DR: In this paper, the enhanced stability of CsPbI3 nanocrystals is achieved by incorporating the Cu2+ ion into the lattice under mild conditions, which can maintain red luminescence for 35 days in air while the undoped ones transformed into the nonluminescent yellow phase in several days.
Abstract: Black phase CsPbI3 perovskites have emerged as one of the most promising materials for use in optoelectronic devices due to their remarkable properties. However, black phase CsPbI3 usually possesses poor stability and involves a phase change process, resulting in an undesired orthorhombic (δ) yellow phase. Here, the enhanced stability of CsPbI3 nanocrystals is achieved by incorporating the Cu2+ ion into the CsPbI3 lattice under mild conditions. In particular, the Cu2+-doped CsPbI3 film can maintain red luminescence for 35 days in air while the undoped ones transformed into the nonluminescent yellow phase in several days. Furthermore, first-principles calculations verified that the enhanced stability is ascribed to the increased formation energy due to the successful doping of Cu2+ in CsPbI3. Benefiting from such an effective doping strategy, the as-prepared Cu2+-doped CsPbI3 as an emitting layer shows much better performance compared with that of the undoped counterpart. The turn-on voltage of the Cu2+-doped quantum-dot light-emitting diode (QLED) (1.6 V) is significantly reduced compared with that of the pristine QLED (3.8 V). In addition, the luminance of the Cu2+-doped QLED can reach 1270 cd/m2, which is more than twice that of the pristine CsPbI3 QLED (542 cd/m2). The device performance is believed to be further improved by optimizing the purification process and device structure, shedding light on future applications.
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TL;DR: Li et al. as mentioned in this paper presented a systematic study across ∼170 photostable single colloidal quantum dots (QDs) of different sizes and compositions, unveiling that increasing quantum confinement is an effective strategy for maximizing single-photon purity due to the suppressed biexciton quantum yield.
Abstract: Attaining pure single-photon emission is key for many quantum technologies, from optical quantum computing to quantum key distribution and quantum imaging. The past 20 years have seen the development of several solid-state quantum emitters, but most of them require highly sophisticated techniques (e.g., ultrahigh vacuum growth methods and cryostats for low-temperature operation). The system complexity may be significantly reduced by employing quantum emitters capable of working at room temperature. Here, we present a systematic study across ∼170 photostable single CsPbX3 (X: Br and I) colloidal quantum dots (QDs) of different sizes and compositions, unveiling that increasing quantum confinement is an effective strategy for maximizing single-photon purity due to the suppressed biexciton quantum yield. Leveraging the latter, we achieve 98% single-photon purity (g(2)(0) as low as 2%) from a cavity-free, nonresonantly excited single 6.6 nm CsPbI3 QDs, showcasing the great potential of CsPbX3 QDs as room-temperature highly pure single-photon sources for quantum technologies.
18 citations
24 Sep 2021
13 citations
TL;DR: In this paper , the authors analyzed the main instability factors of red-emissive perovskite nanocrystals (PNCs), including their structures, optoelectronic properties, and instability mechanism.
Abstract: All-inorganic perovskite nanocrystals (PNCs) have been anticipated to be used in efficient and stable perovskite optoelectronic devices because of their suitable bandgap, broad absorption spectrum, and high color purity. However, long-term stability remains a major obstacle for the commercial application of PNCs. In particular, for red-emissive perovskites, the reaction to the environment is more sensitive than that for the green counterpart, which makes a phase transformation easily occur at room temperature. On the basis of CsPbI3 PNCs, we analyze the main instability factors of red-emissive PNCs (620–720 nm), including their structures, optoelectronic properties, and instability mechanism. We then summarize some strategies to improve the stability and performance of the perovskites and light-emitting diodes (LEDs). Furthermore, we discuss the challenge of scaling up the production of PNCs. Finally, we propose possible perspectives for the development of perovskite materials.
12 citations
TL;DR: In this article , phase-pure, monodispersed, stable and highly luminescent CsPbI3 nanocrystals can be obtained by tweaking the conventional hot-injection method employing NH4I as an additional precursor.
Abstract: Despite their low band gap, the utility of CsPbI3 nanocrystals (NCs) in solar photovoltaic and optoelectronic applications is rather limited because of their phase instability and photoluminescence (PL) intermittency. Herein we show that phase-pure, monodispersed, stable and highly luminescent CsPbI3 NCs can be obtained by tweaking the conventional hot-injection method employing NH4I as an additional precursor. Single-particle studies show a significant suppression of PL blinking. Among all NCs studied, 60% exhibit only high-intensity ON states with a narrow distribution of intensity. The remaining 40% of NCs exhibit a much wider distribution of PL intensity with a significant contribution of low-intensity OFF states. Excellent characteristics of these CsPbI3 NCs are shown to be the result of NH4+ replacing some surface Cs+ of an iodide-rich surface of the NCs. These phase-stable and highly luminescent CsPbI3 NCs with significantly suppressed PL blinking can be useful single-photon emitters and promising materials for optoelectronic and solar photovoltaic applications.
11 citations
01 Nov 2021
9 citations
References
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TL;DR: The compelling combination of enhanced optical properties and chemical robustness makes CsPbX3 nanocrystals appealing for optoelectronic applications, particularly for blue and green spectral regions (410–530 nm), where typical metal chalcogenide-based quantum dots suffer from photodegradation.
Abstract: Metal halides perovskites, such as hybrid organic–inorganic CH3NH3PbI3, are newcomer optoelectronic materials that have attracted enormous attention as solution-deposited absorbing layers in solar cells with power conversion efficiencies reaching 20%. Herein we demonstrate a new avenue for halide perovskites by designing highly luminescent perovskite-based colloidal quantum dot materials. We have synthesized monodisperse colloidal nanocubes (4–15 nm edge lengths) of fully inorganic cesium lead halide perovskites (CsPbX3, X = Cl, Br, and I or mixed halide systems Cl/Br and Br/I) using inexpensive commercial precursors. Through compositional modulations and quantum size-effects, the bandgap energies and emission spectra are readily tunable over the entire visible spectral region of 410–700 nm. The photoluminescence of CsPbX3 nanocrystals is characterized by narrow emission line-widths of 12–42 nm, wide color gamut covering up to 140% of the NTSC color standard, high quantum yields of up to 90%, and radiativ...
6,170 citations
TL;DR: In this article, the authors describe visible-light-emitting perovskite LEDs that surpass the quantum efficiency milestone of 20.3 per cent, which is achieved by a new strategy for managing the compositional distribution in the device.
Abstract: Metal halide perovskite materials are an emerging class of solution-processable semiconductors with considerable potential for use in optoelectronic devices1–3. For example, light-emitting diodes (LEDs) based on these materials could see application in flat-panel displays and solid-state lighting, owing to their potential to be made at low cost via facile solution processing, and could provide tunable colours and narrow emission line widths at high photoluminescence quantum yields4–8. However, the highest reported external quantum efficiencies of green- and red-light-emitting perovskite LEDs are around 14 per cent7,9 and 12 per cent8, respectively—still well behind the performance of organic LEDs10–12 and inorganic quantum dot LEDs13. Here we describe visible-light-emitting perovskite LEDs that surpass the quantum efficiency milestone of 20 per cent. This achievement stems from a new strategy for managing the compositional distribution in the device—an approach that simultaneously provides high luminescence and balanced charge injection. Specifically, we mixed a presynthesized CsPbBr3 perovskite with a MABr additive (where MA is CH3NH3), the differing solubilities of which yield sequential crystallization into a CsPbBr3/MABr quasi-core/shell structure. The MABr shell passivates the nonradiative defects that would otherwise be present in CsPbBr3 crystals, boosting the photoluminescence quantum efficiency, while the MABr capping layer enables balanced charge injection. The resulting 20.3 per cent external quantum efficiency represents a substantial step towards the practical application of perovskite LEDs in lighting and display. A strategy for managing the compositional distribution in metal halide perovskite light-emitting diodes enables them to surpass 20% external quantum efficiency—a step towards their practical application in lighting and displays.
2,346 citations
TL;DR: The demonstration of these novel quantum-dot light-emitting diodes based on all-inorganic perovskite CsPbX3 (X = Cl, Br, I) nanocrystals opens a new avenue toward designing optoelectronic devices, such as displays, photodetectors, solar cells, and lasers.
Abstract: Novel quantum-dot light-emitting diodes based on all-inorganic perovskite CsPbX3 (X = Cl, Br, I) nanocrystals are reported. The well-dispersed, single-crystal quantum dots (QDs) exhibit high quantum yields, and tunable light emission wavelength. The demonstration of these novel perovskite QDs opens a new avenue toward designing optoelectronic devices, such as displays, photodetectors, solar cells, and lasers.
2,311 citations
TL;DR: N nanoscale phase stabilization of CsPbI3 quantum dots (QDs) to low temperatures that can be used as the active component of efficient optoelectronic devices and describe the formation of α-CsP bI3 QD films that are phase-stable for months in ambient air.
Abstract: We show nanoscale phase stabilization of CsPbI 3 quantum dots (QDs) to low temperatures that can be used as the active component of efficient optoelectronic devices. CsPbI 3 is an all-inorganic analog to the hybrid organic cation halide perovskites, but the cubic phase of bulk CsPbI 3 (α-CsPbI 3 )—the variant with desirable band gap—is only stable at high temperatures. We describe the formation of α-CsPbI 3 QD films that are phase-stable for months in ambient air. The films exhibit long-range electronic transport and were used to fabricate colloidal perovskite QD photovoltaic cells with an open-circuit voltage of 1.23 volts and efficiency of 10.77%. These devices also function as light-emitting diodes with low turn-on voltage and tunable emission.
2,103 citations
TL;DR: Here, a critical instability in mesoporous TiO₂-sensitized solar cells arising from light-induced desorption of surface-adsorbed oxygen is identified and it is shown that this instability does not arise in mesosuperstructured solar cells.
Abstract: The power conversion efficiency of hybrid solid-state solar cells has more than doubled from 7 to 15% over the past year. This is largely as a result of the incorporation of organometallic trihalide perovskite absorbers into these devices. But, as promising as this development is, long-term operational stability is just as important as initial conversion efficiency when it comes to the development of practical solid-state solar cells. Here we identify a critical instability in mesoporous TiO₂-sensitized solar cells arising from light-induced desorption of surface-adsorbed oxygen. We show that this instability does not arise in mesoporous TiO₂-free mesosuperstructured solar cells. Moreover, our TiO₂-free cells deliver stable photocurrent for over 1,000 h continuous exposure and operation under full spectrum simulated sunlight.
1,569 citations