LiJiong

Perovskite quantum dot paper, a new type of perovskite quantum dot film, is demonstrated. Using a simple, fast, scalable, and inexpensive paper fabrication process, the resulting perovskite quantum dot paper is uniform, of high quality, and very stable; it is able to bear high energy radiation and greatly improve the efficiency of perovskite quantum dot–based white light‐emitting diodes.

Abstract

Perovskite quantum dots (PQDs) are a competitive candidate for next‐generation display technologies as a result of their superior photoluminescence, narrow emission, high quantum yield, and color tunability. However, due to poor thermal resistance and instability under high energy radiation, most PQD‐based white light‐emitting diodes (LEDs) show only modest luminous efficiency of ≈50 lm W⁻¹ and a short lifetime of <100 h. In this study, by incorporating cellulose nanocrystals, a new type of QD film is fabricated: CH₃NH₃PbBr₃ PQD paper that features 91% optical absorption, intense green light emission (518 nm), and excellent stability attributed to the complexation effect between the nanocellulose and PQDs. The PQD paper is combined with red K₂SiF₆:Mn4⁺ phosphor and blue GaN LED chips to fabricate a high‐performance white LED demonstrating ultrahigh luminous efficiency (124 lm W⁻¹), wide color gamut (123% of National Television System Committee), and long operation lifetime (240 h), which paves the way for advanced lighting technology.

Fully transparent inverted quantum dot light-emitting diodes (QLEDs) were fabricated by incorporating a Ag-nanowire-based anode. Aluminum-doped zinc oxide (ZnO:Al, AZO) was inserted by atomic layer deposition and reduced the sheet resistance by promoting adhesion of Ag nanowires (AgNWs) film and increasing its chemical stability towards oxygen. The performance of the QLEDs was optimal when the thickness of AZO was 20 nm. The current efficiency of the fully transparent inverted QLEDs integrated with the AgNWs/AZO anode reached 15.33 cd A −1 . The main peak wavelength and optical transmittance of the inverted QLEDs were 530 nm and 75.66%, respectively. This discovery is expected to provide a basic method for the production of flexible displays with full transparency by AgNWs-based electrodes.

Ruddlesden–Popper 2D perovskites with a formula of (A′)₂(A) _{n −1}B _n X_{3 n +1} are excellent materials for the next generation of optoelectronic devices. Their properties can be tuned by selecting different organic amines, metal halides, and number of layers for light‐emitting diodes and solar cells.

Abstract

Ruddlesden–Popper perovskites with a formula of (A′)₂(A) _{n −1}B _n X_{3 n +1} have recently gained widespread interest as candidates for the next generation of optoelectronic devices. The variations of organic cation, metal halide, and the number of layers in the structure lead to the change of crystal structures and properties for different optoelectronic applications. Herein, the different synthetic methods for 2D perovskite crystals and thin films are summarized and compared. The optoelectronic properties and the charge transfer process in the devices are also delved, in particular, for light‐emitting diodes and solar cells.

Self-driven photodetectors are widely used in communication and imaging. As a newly developed semiconductor material, perovskite quantum dots (QDs) are not only bandgap tunable, but also easily combined with other materials. In this paper, a vertical structure self-driven photodetector based on heterojunction of CsPbBr 3 QDs and PbS QDs is proposed, and the device is prepared by solution spin coating method. The device can work in visible and near infrared (400–1130 nm) regions, and has excellent performance, such as ultrafast response speed (rise and decay time are 0.4 μ s/0.73 μ s under 532 nm laser irradiation in self-driven mode, the estimated response time under 1064 nm laser irradiation is about 11.5 μ s), more than 100 dB linear dynamic range for both visible and infrared regions, and good stability. Similarly, the responsivity of the photodetector can also reach an average of 10 mA W −1 , and the detectivity is 1.13 × 10 10 ...

Nature Communications, Published online: 03 October 2019; doi:10.1038/s41467-019-12513-x

Tin-based perovskites possess the suitable narrow-bandgap for tandem solar cells but their short carrier diffusion lengths limit device efficiency. Here Yang et al. add cadmium ions to increase diffusion length to above 2 µm by reducing the background free hole concentration and electron trap density.

Nature Communications, Published online: 09 October 2019; doi:10.1038/s41467-019-12613-8

Charged surface defects are expected to undermine the charge extraction in organic-inorganic perovskite solar cells. Here Zhang et al. design ionic fullerene derivatives to not only passivate the charged defects, but also optimize the interfacial energy due to aligned orientation of the fullerenes.