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Halide perovskites have been proven to have enormous potential for further flexible optoelectronic devices. However, the repeated mechanical bending and tolerance to moisture corrosion remain a critical challenge for flexible perovskite devices. Solution chemistry of a precursor is the basis for the preparation of high-quality perovskite films and can significantly enhance the lasing performance and humidity stability of perovskites. Herein, from the perspective of solvent engineering, two ionic liquids (ILs) of methylammonium acetate (MAAc) and methylammonium propionate (MAP) were introduced to prepare high-quality MAPbBr3 perovskite films. The as-prepared MAPbBr3 perovskite films exhibit not only enhanced amplified spontaneous emission (ASE) performance but also the excellent mechanical reliability even in a humid environment. Especially, the MAAc-based MAPbBr3 perovskite film possesses the morphology optimization, defect passivation, simultaneous improvements in ASE, and bending durability due to the stronger coordination capacity and reactivity between MAAc and Pb2+. Our work provides an effective strategy for flexible perovskite based photonic devices fueled by the remarkable mechanical reliability. [ABSTRACT FROM AUTHOR]

Cesium lead bromide (CsPbBr3) perovskite has attracted great attention recently for its potentials for next-generation green-color lasing devices owing to the relatively high structural stability and the high emission efficiency among the perovskite family. Herein, we explore the origins of cavity modes in CsPbBr3 microplatelets (MPs) lasers by using angle-resolved microphotoluminescence Fourier imaging technique, which is still controversial so far. In-plane Fabry–Pérot (F-P) mode lasing transition to whispering-gallery-mode (WGM) lasing is verified at room temperature, which mostly occurs in large MPs with edge length (L) over 13 μm. The F-P lasing is suppressed upon decreasing L or increasing excitation density, and the WGM lasing is predominant for all MPs at high excitation density. Furthermore, the parity and symmetry of in-plane F-P modes are classified. These results advance the fundamental understanding of lasing modes in planar microcavities as well as their applications in on-chip interconnection and quantum optics. [ABSTRACT FROM AUTHOR]

Herein, the piezoelectric effect of CsPbBr3 perovskite is utilized for the first time to enhance the nanolasers performance based on the flexible poly(ethylenenaphthalate) PEN/single‐crystal‐Au/MgF2/CsPbBr3 (ScAu/M/CPB) structure. The dynamic‐modulated plasmonic lasing mode blueshift is achieved by the piezoelectric polarization effect (PPE)‐induced effective refractive index (neff) change by varying the applied strain (ε). In particular, taking advantage of the increased cavity mode frequency, the lasing threshold (Pth) reduces from 4.5 µJ cm−2 (ε = 0) to 1.5 µJ cm−2 (ε = −1.02%). The ε‐dependent carrier dynamics results reveal the nature of ultralow Pth being PPE‐induced spontaneous emission (SE) decay rate enhancement, leading to the reduction in radiation loss of the plasmonic cavity. The corresponding enhancement mechanism is put forward to elucidate the principle of piezoelectric‐induced dynamic modulation nanolasers characteristic. This work demonstrates that coupling of piezoelectric effect and plasmonics is an effective route to enhance the performance of plasmonic nanolasers. [ABSTRACT FROM AUTHOR]

Perovskite colloidal quantum wells (QWs) are promising to realize narrow deep‐blue emission, but the poor optical performance and stability suppress their practical application. Here, we creatively propose a water‐driven synthesis strategy to obtain size‐homogenized and strongly confined deep‐blue CsPbBr3 QWs, corresponding to three monolayers, which emit at the deep‐blue wavelength of 456 nm. The water controls the orientation and distribution of the ligands on the surface of the nanocrystals, thus inducing orientated growth through the Ostwald ripening process by phagocytizing unstable nanocrystals to form well‐crystallized QWs. These QWs present remarkable stability and high photoluminescence quantum yield of 94 %. Furthermore, we have prepared light‐emitting diodes based on the QWs via the all‐solution fabrication strategy, achieving an external quantum efficiency of 1 % and luminance of 2946 cd m−2, demonstrating state‐of‐the‐art brightness for perovskite QW‐based LEDs. [ABSTRACT FROM AUTHOR]

Perovskite colloidal quantum wells (QWs) are promising to realize narrow deep‐blue emission, but the poor optical performance and stability suppress their practical application. Here, we creatively propose a water‐driven synthesis strategy to obtain size‐homogenized and strongly confined deep‐blue CsPbBr3 QWs, corresponding to three monolayers, which emit at the deep‐blue wavelength of 456 nm. The water controls the orientation and distribution of the ligands on the surface of the nanocrystals, thus inducing orientated growth through the Ostwald ripening process by phagocytizing unstable nanocrystals to form well‐crystallized QWs. These QWs present remarkable stability and high photoluminescence quantum yield of 94 %. Furthermore, we have prepared light‐emitting diodes based on the QWs via the all‐solution fabrication strategy, achieving an external quantum efficiency of 1 % and luminance of 2946 cd m−2, demonstrating state‐of‐the‐art brightness for perovskite QW‐based LEDs. [ABSTRACT FROM AUTHOR]

Semiconductor micro/nano-cavities with high quality factor (Q) and small modal volume provide critical platforms for exploring strong light-matter interactions and quantum optics, enabling further development of coherent and quantum photonic devices. Constrained by exciton binding energy and thermal fluctuation, only a handful of wide-band semiconductors such as ZnO and GaN have stable excitons at room temperature. Metal halide perovskite with cubic lattice and well-controlled exciton may provide solutions. In this work, high-quality single-crystalline cesium lead halide CsPbX3 (X = Cl, Br, I) whispering-gallery-mode (WGM) microcavities are synthesized by vapor-phase van der Waals epitaxy method. The as-grown perovskites show strong emission and stable exciton at room temperature over the whole visible spectra range. By varying the halide composition, multi-color (400-700 nm).WGM excitonic lasing is achieved at room temperature with low threshold (~ 2.0 μJ cm−2) and high spectra coherence (~0.14-0.15 nm). The results advocate the promise of inorganic perovskites towards development of optoelectronic devices and strong light-matter coupling in quantum optics. [ABSTRACT FROM AUTHOR]

Quasi‐2D perovskite solar cells have recently emerged as a highly prospective and inexpensive solution for sustainable energy due to their intrinsic optoelectronic properties and stability. The qualities of these promising quasi‐2D perovskite cells are generally affected by different intermediates derived from the precursor solution during film fabrication processing. However, efficient solutions to inhibit intermediates remain insufficient to date. Here, an effective strategy is prsented to inhibit the growth of 1D solvate intermediate during the fabricating process of quasi‐2D perovskite films by introducing a guanidinium thiocyanate (GUASCN) inhibitor. Theoretical calculations reveal that the SCN− anions spontaneously replace the iodide ions in the inorganic framework [PbI6]3− and induce the decomposition of the solvate intermediate. The resulted perovskite solar cells exhibit a significant improvement in power conversion efficiency (PCE), benefiting from the reduced trap‐state density and enhanced carrier mobilities. The unencapsulated devices retain 91% and 95% of the original PCEs under 45 ± 10% humidity in air or under continuous light irradiation at 100 mW cm−2 and 45 °C in a nitrogen atmosphere for 1000 h. Particularly, devices without electron‐transporting layers maintain 85% of the peak PCE under maximum power point tracking at 45 °C for 1000 h. [ABSTRACT FROM AUTHOR]

Ruddlesden–Popper phase 2D perovskite solar cells (PSCs) exhibit improved lifetime while still facing challenges such as phase alignment and up‐scaling to module‐level devices. Herein, polyelectrolytes are explored to tackle this issue. The contact between perovskite and hole‐transport layer (HTL) is important for decreasing interfacial non‐radiative recombination and scalable fabrication of uniform 2D perovskite films. Through exploring compatible butylamine cations, we first demonstrate poly(3‐(4‐carboxybutyl)thiophene‐2,5‐diyl)‐butylamine (P3CT‐BA) as an efficient HTL for 2D PSCs due to its great hydrophilicity, relatively high hole mobility and uniform surface. More importantly, the tailored P3CT‐BA has an anchoring effect and acts as the buried passivator for 2D perovskites. Consequently, a best efficiency approaching 18 % was achieved and we further first report large‐area (2×3 cm2, 5×5 cm2) 2D perovskite minimodules with an impressive efficiency of 14.81 % and 11.13 %, respectively. [ABSTRACT FROM AUTHOR]

Ruddlesden–Popper phase 2D perovskite solar cells (PSCs) exhibit improved lifetime while still facing challenges such as phase alignment and up‐scaling to module‐level devices. Herein, polyelectrolytes are explored to tackle this issue. The contact between perovskite and hole‐transport layer (HTL) is important for decreasing interfacial non‐radiative recombination and scalable fabrication of uniform 2D perovskite films. Through exploring compatible butylamine cations, we first demonstrate poly(3‐(4‐carboxybutyl)thiophene‐2,5‐diyl)‐butylamine (P3CT‐BA) as an efficient HTL for 2D PSCs due to its great hydrophilicity, relatively high hole mobility and uniform surface. More importantly, the tailored P3CT‐BA has an anchoring effect and acts as the buried passivator for 2D perovskites. Consequently, a best efficiency approaching 18 % was achieved and we further first report large‐area (2×3 cm2, 5×5 cm2) 2D perovskite minimodules with an impressive efficiency of 14.81 % and 11.13 %, respectively. [ABSTRACT FROM AUTHOR]

Near-infrared (NIR) solid-state micro/nanolasersare importantbuilding blocks for true integration of optoelectronic circuitry.1 Although significant progress has been made inIII–V nanowire lasers with achieving NIR lasing at room temperature,2−4 challenges remain including low quantum efficiencies and high Augerlosses. Importantly, the obstacles toward integrating one-dimensionalnanowires on the planar ubiquitous Si platform need to be effectivelytackled. Here we demonstrate a new family of planar room-temperatureNIR nanolasers based on organic–inorganic perovskite CH3NH3PbI3-aXa(X = I, Br, Cl)nanoplatelets. Their large exciton binding energies, long diffusionlengths, and naturally formed high-quality planar whispering-gallerymode cavities ensure adequate gain and efficient optical feedbackfor low-threshold optically pumped in-plane lasing. We show that theseremarkable wavelength tunable whispering-gallery nanolasers can beeasily integrated onto conductive platforms (Si, Au, indium tin oxide,and so forth). Our findings open up a new class of wavelength tunableplanar nanomaterials potentially suitable for on-chip integration. [ABSTRACT FROM AUTHOR]

All‐inorganic CsPbX3 (X = Cl, Br, I, or mixed halides) perovskite quantum dots (QDs) exhibit tunable optical bandgaps and narrow emission peaks, which have received worldwide interest in the field of both photovoltaics (PVs) and light‐emitting diodes (LEDs). Herein, it is reported a discovery that CsPbI3 perovskite QD solar cell can simultaneously deliver high PV performance and intense electroluminescence. In specific, the multifunctional CsPbI3 QD film is fabricated through a simple yet efficient solid‐state‐ligand exchange process using a tailored organic ligand triphenyl phosphite (TPPI). The function of QD surface manipulation using TPPI here is proven to be twofold, balancing the carrier transport and effectively passivating the QD surface to produce conductive and emissive QD film. The CsPbI3 perovskite QD solar cell delivers a champion efficiency of 15.21% with improved open circuit voltage and high fill factor. Concurrently functioning as a red LED, the CsPbI3 perovskite QD solar cell outputs electric power to light conversion efficiency approaching 4%, a record value for QD electroluminescent PVs. The results here indicate that these versatile perovskite QDs may be a promising candidate for fabricating multifunctional optoelectronic devices. [ABSTRACT FROM AUTHOR]

Green and amplified spontaneous emissions with low thresholds are crucial for the development of solution‐processable perovskite light sources. Although mixed‐cation CsPbBr3 perovskites are highly promising, pinholes are inevitably formed during the spin‐coating process, which results in considerable optical losses. This study proposes a solvent recrystallization strategy to reduce the number of pinholes and enhance the crystallinity of (Cs, FA, MA)PbBr3/NMA (FA = CH(NH2)2, MA = CH3NH3, and NMA = C11H9NH3) films in a dimethyl sulfoxide gas environment. Amplified spontaneous green emissions are produced with a low threshold of 1.44 μJ cm−2 and a high net modal gain of 1176 cm−1. The reduced threshold is attributed to the relatively low propagation loss and suppressed Auger recombination, which results from the formation of a pinhole‐free surface and enlarged grain size. These results can be utilized in the development of high‐performance perovskite laser devices. [ABSTRACT FROM AUTHOR]

A solution‐processed thin film made of all‐inorganic CsPbBr3 perovskite is a promising candidate for low‐cost and flexible green‐color lasers. However, the amplified spontaneous emission (ASE) of solution‐processed CsPbBr3 films still experiences a high threshold owing to poor morphology and insufficient optical gain. Here, a multiple‐cation doping strategy is demonstrated to develop compact, smooth thin films of Cs0.87(FAMA)0.13PbBr3/(NMA)2PbBr4 (FA: formamidinium; MA: methylammonium; NMA: naphthylmethylammonium) with a record high net modal optical gain of ≈3030 cm−1 and low propagation loss of 1.0 cm−1. The FA and MA cations improve the crystallization kinetics to form continuous films, and the NMA cations reduce the grain dimension, increase film dispersibility/uniformity, and enhance spatial confinement to promote optical gain. Room‐temperature ASE is demonstrated under a low threshold of ≈3.8 µJ cm−2 without degradation after four months of storage in glove box or excitation by 3 × 107 laser pulses. These findings provide insights into enhancing the optical gain and lowering the threshold of perovskite lasers in terms of molecular synthesis and microstructure engineering. [ABSTRACT FROM AUTHOR]

Hybrid organic‐inorganic halide perovskites are actively pursued for optoelectronic technologies, but the poor stability is the Achilles' heel of these materials that hinders their applications. Very recently, it has been shown that lead sulfide (PbS) quantum dots (QDs) can form epitaxial interfaces with the perovskite matrix and enhance the overall stability. In this work, it is demonstrated that embedding QDs can significantly modify the transport property of pristine perovskite single crystals, endowing them with new functionalities besides being structurally robust and free from grain boundaries. Resistive switching memory devices are constructed using solution‐processed CH3NH3PbBr3 (MAPbBr3) perovskite single crystals and the QD‐embedded counterparts. It is found that QDs could significantly enhance the charge transport and reduce the current–voltage hysteresis. The pristine singe crystal device exhibits negative differential resistance, while the QD‐embedded crystals are featured with filament‐type switching behavior and much improved device stability. This study underscores the potential of QD‐embedded hybrid perovskites as a new media for advanced electronic devices. [ABSTRACT FROM AUTHOR]

Exploring the exciton-phonon interaction of cesium lead bromide (CsPbBr3) perovskite nanowires (NWs) is not only important to the fundamental understanding of phonon-assisted carrier dynamics but also critical for the development of high performance miniaturized light sources. Herein, we systematically investigated the temperature (T) dependent spontaneous emission (SE) and lasing spectra of chemical vapor deposited CsPbBr3 NWs. We demonstrated that both the SE and the lasing energy were mainly determined by two facts: the electron-phonon interaction (EP) and the lattice thermal expansion (TE). The lattice TE effect plays a key role at T ∼ 78–170 K, therefore both the lasing and SE peaks exhibit a nearly linear blueshift with increasing T. As T > 195 K, the EP interaction becomes dominant, which reduces the blueshift rate of the SE peak and causes a redshift of lasing peaks. These findings will further advance the understanding of the exciton-phonon interaction and the T-dependence of emission properties of lasers and related optoelectronic devices. [ABSTRACT FROM AUTHOR]

Organolead halide perovskites (e.g., CH3NH3PbI3) have caught tremendous attention for their excellent optoelectronic properties and applications, especially as the active material for solar cells. Perovskite crystal quality and dimension is crucial for the fabrication of high-performance optoelectronic and photovoltaic devices. Herein the controlled synthesis of organolead halide perovskite CH3NH3PbI3 nanoplatelets on SiO2/Si substrates is investigated via a convenient two-step vapor transport deposition technique. The thickness and size of the perovskite can be well-controlled from few-layers to hundred nanometers by altering the synthesis time and temperature. Raman characterizations reveal that the evolutions of Raman peaks are sensitive to the thickness. Furthermore, from the time-resolved photoluminescence measurements, the best optoelectronic performance of the perovskite platelet is attributed with thickness of ≈30 nm to its dominant longest lifetime (≈4.5 ns) of perovskite excitons, which means lower surface traps or defects. This work supplies an alternative to the synthesis of high-quality organic perovskite and their possible optoelectronic applications with the most suitable materials. [ABSTRACT FROM AUTHOR]

Back Cover: Tailoring Phase Alignment and Interfaces via Polyelectrolyte Anchoring Enables Large-Area 2D Perovskite Solar Cells (Angew. 2D Perovskites, Polyelectrolytes, Ruddelsden-Popper Phase, Solar Cells The tailored polyelectrolyte has an anchoring effect and acts as a passivator for 2D perovskites, which can improve 2D perovskite phase alignment and interfacial charge transfer efficiency, and finally enables high-efficiency and large-area 2D perovskite solar cells. [Extracted from the article]

Keywords: 2D Perovskites; Polyelectrolytes; Ruddelsden-Popper Phase; Solar Cells EN 2D Perovskites Polyelectrolytes Ruddelsden-Popper Phase Solar Cells 1 1 1 09/01/22 20220905 NES 220905 B Eine Polyelektrolyt-Lochtransportschicht b für 2D-Perowskit-Solarzellen unter Verwendung eines kompatiblen Butylamin-Kations wurde von Jianyu Yuan und Mitarbeitern in ihrem Forschungsartikel untersucht (e202205111). Rücktitelbild: Tailoring Phase Alignment and Interfaces via Polyelectrolyte Anchoring Enables Large-Area 2D Perovskite Solar Cells (Angew. 2D Perovskites, Polyelectrolytes, Ruddelsden-Popper Phase, Solar Cells. [Extracted from the article]

2D layered halide perovskites have attracted significant attention. Apart from the linear optical properties, it is also intriguing to explore the nonlinear optics of 2D layered halide perovskites and their heterostructures. Previous nonlinear optical (NLO) studies of 2D perovskites primarily focus on the thin films or microplates. Herein, the NLO properties of (n‐C4H9NH3)2PbI4/(n‐C4H9NH3)2(CH3NH3)Pb2I7 heterostructures with centimeter size are systematically studied. The NLO properties can be continuously tuned by changing the thickness. A giant two‐photon absorption (2PA) coefficient up to 44 cm MW−1 is obtained for the heterostructures with a total thickness of 20 µm based on the nonlinear transmittance measurement. Additionally, strong multiphoton‐induced photoluminescence is observed in the heterostructures. It is proposed that the giant 2PA coefficient might arise from the small thickness (≈1 µm) of (n‐C4H9NH3)2(CH3NH3)Pb2I7 layer and possibly the nonradiative energy transfer between the different constituting layers within the heterostructures through an antenna‐like effect. Finally, benefiting from the giant 2PA coefficient, direct detection of 980 nm light is demonstrated with a responsivity of 10−7 A W−1 in the heterostructures. The findings suggest the promising applications of 2D perovskite heterostructures in the infrared photodetection and some other nonlinear absorption related optoelectronic devices. [ABSTRACT FROM AUTHOR]