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Employing a 2-phenylfuro[2,3-b]quinoxaline scaffold as a fluorophore, and phenyl, biphenyl, anthracene and benzothiadiazole as π-linkers, Ph-dFQ, bPh-dFQ, ADN-dFQ and Bth-dFQ were constructed, along with BIZ-FQ with a benzimidazole unit, to screen suitable blue emitters.

Blue emitters with various electron-donors attached to the 9-phenyl-9-phosphafluorene oxide (PhFIOP) moiety and their thermally activated delayed fluorescence (TADF) behavior.

This minireview discloses the underlying challenges of perovskite indoor photovoltaics and summarizes the advanced strategies for indoor efficiency improvement.

Pancreatic cancer (PC) is the most hypoxic cancer type among solid tumors. The dynamic changes of RNA N6-methyl-adenosine (m6A) contribute to tumor cells adaption to hypoxic microenvironmental. However, the regulatory mechanisms of hypoxia response in PC remains elusive. Here, we reported that the m6A demethylase ALKBH5 mediated a decrease of total mRNA m6A modification during hypoxia. Subsequently, methylated RNA immunoprecipitation sequencing (MeRIP-seq) combined with RNA sequencing (RNA-seq) revealed transcriptome-wide gene expression alteration and identified histone deacetylase type 4 (HDAC4) as a key target gene of m6A modification under hypoxic conditionds. Mechanistically, m6A methylation recognized by m6A reader-YTHDF2 enhanced the stability of HDAC4, and then promoted glycolytic metabolism and migration of PC cells. Our assays also demonstrated that hypoxia-induced HDAC4 enhanced HIF1a protein stability, and overexpressed HIF1a promoted transcription of ALKBH5 in hypoxic pancreatic cancer cells. Together, these results found a ALKBH5/HDAC4/HIF1α positive feedback loop for cellular response to hypoxia in pancreatic cancer. Our studies uncover the crosstalk between histone acetylation and RNA methylation modification on layer of epigenetic regulation.

Conjugated and short-molecule capping ligands have been demonstrated as a valid strategy for achieving high-efficiency perovskite nanocrystal (NCs) light-emitting diodes (LEDs) owing to their advantage of allowing efficient carrier transport between NCs. However, monotonously utilizing conjugated ligands cannot achieve sufficient surface modification/passivation for perovskite NCs, leading to their poor photoluminescence quantum yield (PLQY) and dispersibility. This work designs a complementary ligand synthesis method to obtain high-quality methylamine lead bromide (MAPbBr

Two novel molecular scaffolds, dibenzo[f,h]furo[2,3-b]quinoxaline (diBFQ) and its derivative, 3,6-bis(4-isopropylphenyls)-11-phenyldibenzo[f,h]furo[2,3-b]quinoxaline (dP-diBFQ), and furo[2',3':5,6]pyrazino[2,3-f][1,10]phenanthroline (FPPhen), were designed and syn-thesized for highly efficient pure and deep blue emission. The unsubstituted molecule scaffold diBFQ and FPPhen exhibit 424~445 nm emission with ~70% PLQY, and disubstituted derivative of diBFQ, dP-diBFQ, shows 79.1% PLQY. Our experimental and theoretical investigations re-vealed the additional N atoms in FPPhen facilitate electron distribution of HOMO orbital localizing on smaller π-conjugate fragment as com-pared with diBFQ, which resulted in emission peak blue-shifting from 445 nm of diBFQ to 424 nm of FPPhen. Furthermore, introducing the steric substituent isopropylphenyl into diBFQ scaffold would help to suppress aggregate of dP-diBFQ molecules and improve fluorescence efficiency. The OLEDs using dP-diBFQ as dopants shows pure blue emission with a CIE coordinates (0.154, 0.102) and an EQE of 2.28%. In-creasing dopant concentration, the EQE and current efficiency could be improved to 2.63 % and 4.7 cd/A, but aggregate emission with a peak of 472~476 nm was clearly observed due to molecular aggregate. Our studies clearly suggested that diBFQ and FPPhen scaffolds are promising fluorescence core for deep and pure-blue emissions.

We report here two new centimetric two-dimensional Dion–Jacobson bromide double perovskites with outstanding stability, strong photocurrent responses and bluish-white broadband emission.

An approach was presented to suppress T1-state energy loss in OLEDs. That is developing comparable T1-energy FD with TADF co-host, and thus, T1 excitons on the FDs would escape and go back to the co-host and then transfer to the singlet state of the FDs, finally contributing to light-emission.

Cs5Cu3Cl6I2 nanocrystals exhibit a blue light emission with a high PLQY of 73.7%. Multiple self-trapped excitons are proposed to be responsible for the peculiar emission originating from various Cu–Cu interactions on one-dimensional chains.

We have demonstrated that the T1-state energy of a fluorescence dopant (FD) is close to that of the thermally activated delayed fluorescence (TADF)-type exciplex co-host, and the energy loss caused by the T1 states of the FD could be suppressed in TADF-sensitized fluorescence (TSF) OLEDs.

Two-dimensional (2D) organic–inorganic hybrid materials have attracted widespread attention for photodetection. Moreover, such materials with broadband photoluminescence and strong photocurrent response are still rare. Here, we report two new semiconducting 2D organic–inorganic hybrid materials, namely {PbII2I6[PbII(TETA)]}n (1Pb) and {PbII3I8[PbII(TETA)]}n (2Pb), where TETA = triethylenetetramine, with broadband yellow-green emission. Both compounds are soluble in DMF and yield high surface coverage films through spin coating. Strikingly, the photocurrent responses of such thin films show ca. 600 and 700 nA cm−2 difference between Ilight and Idark for 1Pb and 2Pb, respectively. To the best of our knowledge, 1Pb and 2Pb showed among the highest current obtained in 2D lead iodide hybrid materials under a low voltage (0.7 V). Moreover, 1Pb and 2Pb are stable under heat, moisture and light, which may provide realistic applications for light detection.

Formamidinium (FA)-based perovskites have demonstrated excellent advances in optoelectronics recently, but in terms of perovskite compounds, the optimal condition of their composition optimization remains controversial. Herein, we boosted the performance of perovskite light-emitting diodes (PeLEDs) in both efficiency and stability through composition and phase engineering. The low-dimensional FA2PbBr4 particles emerged and mixed with the FAPbBr3 composites when the FABr content is excessive. By regulating the phase composition in multiphase FAPbBr3 perovskites, the maximum external quantum efficiency (EQEmax) of optimal PeLEDs (5.14%) is 2.7-fold higher than that of pure FAPbBr3-based PeLEDs (1.90%), and device stability is improved. Further optimizing the film quality and emission efficiency with Rb+ ions, the EQEmax of PeLEDs can be increased to 6.01%, with a half-lifetime of about 185 s under the high current density. This strategy of phase composition optimization in FA-based perovskites provides an effective way to process high-efficiency and stable PeLEDs.

We studied the inhibitory effects of allelochemicals extracted from celery (Apium graveolens L.) rotten roots and rhizosphere soil on Fusarium oxysporum f. sp. cucumerinum (FOC). The allelochemicals were extracted and separated by column chromatography from the acetone extracts of celery rotten roots and rhizosphere soil. After extraction each fraction was mixed with potato dextrose agar (PDA) culture medium and then inoculated with FOC. The best fraction was screened by measuring the colony diameter and its effects on FOC was determined by evaluating the activities of antioxidant enzymes. The allelochemicals of best fractions were detected using GC-MS. The best fractions obtained after second run in column chromatography were labeled as RRA32, RRA38, RRA101, RRA102 and RRSA55, RRSA56, RRSA105, RRSA106 and they had allelopathic potential of 29.68 %, 31.97 %, 40.38 %, 41.55 % and 29.51 %, 29.47 %, 29.30 % and 32.85 % respectively. The antioxidants enzymes (peroxidase, catalase and superoxide dismutase) activities were significantly lower in treated FOC than control. Using the 8-best fractions, the GC-MS analysis yielded, total 47 compounds viz., 7 organic acids, 17 esters, 1 phenol, 1 alcohol, 1 aldehyde, 5 nitrogen-containing compounds and 2 carbides.

Perovskite materials display great potential in the optoelectronic applications and are considered as one of the most promising optoelectronic materials due to the advantages such as high color-rending index, wide color gamut, excellent charge-transport properties, adjustable band gap, high photoluminescence quantum efficiency, low manufacturing cost, and compatibility with flexible/stretchable devices. Applying perovskite QDs as phosphors in white light down-converted light- emitting diode (LED) or emitter materials in active matrix-QLEDs to obtain high efficiency and wide color gamut is significantly promising for next-generation high-definition information displays and high-quality lighting sources applications. In this paper, the evolution of device performance of perovskite QDs-based LEDs has been demonstrated. Significant enhancement of device performance has been realized through appropriate ligand choice and effective ligand exchange together with modifying device architectures. Meanwhile, numerous encouraging achievements have been achieved via inhibition of non-radiative recombination and enhancement of exciton binding energy, since the first perovskite LED was reported in 2014. Due to the quantum effect limited by space size, perovskite quantum dots have higher exciton binding energy, easily achievable high fluorescence quantum efficiency and narrow emission bandwidth. Because of the excellent photoelectric characteristics, perovskite quantum dots have a wide application potential in new display and solid state lighting. However, for the commercial applications, further efforts are required to elucidate the physical mechanisms and improve the device performance of perovskite QLEDs. Besides, the poor stability of perovskite QLEDs in ambient and harsh conditions has attracted a wide concern, and simultaneously, several strategies have been explored to circumvent this issue, including compositional engineering, surface engineering, matrix encapsulation and device encapsulation. Although significant advances have been made in this regard, the lifetime of perovskite QLEDs remains far away from the commercial requirements. Further strategies to stabilize perovskite QDs and prevent their decomposition are in demand. Encapsulation technology of such kind of devices should be further investigated. Moreover, to avoid the toxicity problem, stable lead-free metal halide analogues with high optoelectronic performance are also needed. Furthermore, colloidal perovskite QDs can maintain functionality under tensile strains, opening new possibilities for their applications in flexible/stretchable electronics to satisfy the future development trend of QLEDs. In recent years, perovskite quantum dots have become an important issue in the field of photoelectricity. The device performance of perovskite quantum dot light-emitting diode has advanced considerably. In this paper, the research progress of perovskite quantum dot electroluminescence devices is reviewed, the main factors restricting the electroluminescence performance of perovskite quantum dots are analyzed, and in view of the problems in devices: Poor charge transport caused by long-chain ligands, non-radiative quenching of excitons caused by surface defects, and imbalance of charge injection in devices, the improvement strategies are discussed separately. Due to the quantum effect limited by space size, perovskite quantum dots have higher exciton binding energy, easily achievable high fluorescence quantum efficiency and narrow emission bandwidth. Compared with perovskite orebody materials, perovskite quantum dots have greater application potential in the field of display and lighting. And we are convinced that a highly efficient and stable perovskite QDs-based LED will be fulfilled in the near future.

Inspired by the intriguing optoelectronic characteristics of the 2-phenylpyridine-type (ppy-type) four-coordinate organoboron skeleton, we envisage a molecular design strategy by manipulating the MLCT transition character to develop high-performance long-wavelength Ir-based phosphors with a ppy-type four-coordinate organoboron skeleton for organic light-emitting diodes (OLEDs). Three ppy-type cyclometalated Ir(III) complexes are successfully prepared. IrOBN and IrPBN exhibit the expected long-wavelength phosphorescent emission at 620 and 604 nm, respectively, due to the electron-accepting ability of the pyridine coordinated with the boron atom (pyd(B)) in extending the π-conjugated length for the LUMO, thus leading to stabilization of the LUMO. Interestingly, IrMBN shows a green phosphorescence at 514 nm. The more electron-deficient pyd(B) in IrMBN leads to a reorganized and localized LUMO distribution pattern mainly on pyd(B) rather than the pyridine coordinated with the Ir atom (pyd(Ir)), shortening the π-conjugation length for the LUMO, hence resulting in an elevated LUMO. Benefiting from the high rigidity of the ppy-type four-coordinate organoboron skeleton, these three ppy-type cyclometalated Ir(III) complexes show high PLQY (ca. 0.6–1). Beneficially, we can achieve impressive electroluminescence (EL) performance based on IrPBN with the highest efficiencies of a maximum external quantum efficiency (ηext) of 26.0%, a maximum current efficiency (ηL) of 42.0 cd A−1, and a maximum power efficiency (ηP) of 38.5 lm W−1, respectively. All these excellent results convincingly demonstrate the effectiveness of our molecular design strategy and the great potential of the ppy-type four-coordinate organoboron skeleton in developing high-performance Ir-based phosphors.

A series of four-coordinated PtII(C^N)(N-donor ligand)Cl-type complexes have been synthesized through combination between C^N-type and N-donor ligands with different sizes. Photophysical features, electrochemical behaviors and electroluminescent (EL) performances have been investigated in detail. Critically, the relationship between the size of organic ligands and aggregation-induced phosphorescence emission (AIPE) behaviors for these PtII(C^N)(N-donor ligand)Cl-type complexes has been characterized. With extending the dimensions of the C^N-type and/or N-donor ligands, the AIPE of these PtII(C^N)(N-donor ligand)Cl-type complexes is more likely to show up with lower H2O volumetric fractions (fw) in the THF solution of these complexes. These unique AIPE experimental results have clearly revealed a new AIE mechanism called restrained D2d deformation of the coordinating skeleton of these PtII(C^N)(N-donor ligand)Cl-type complexes from square-planar (D4h) in the ground states to the tetrahedron (Td) skeleton in the excited states. In addition, solution-processed organic light-emitting diodes (OLEDs) based on these AIPE emitters have been fabricated to characterize their EL potential. Impressive EL efficiencies with the maximum external quantum efficiency (ηext) of 25.2%, current efficiency (ηL) of 53.9 cd A−1 and power efficiency (ηP) of 43.5 lm W−1 can be achieved, indicating great potential of these PtII(C^N)(N-donor ligand)Cl-type AIPE emitters in the field of OLEDs. Importantly, this research has proposed a new AIE mechanism to promote the development of new phosphorescent AIPE complexes with great potential in the field of OLEDs.

Lead-based semiconducting organic–inorganic halides such as CH3NH3PbI3 are promising materials for optoelectronic applications. However, the toxicity of lead and the instability of these materials could raise environmental issues if they are applied on a large scale. Herein, two new 2D lead-free bimetallic iodide-based hybrid compounds are presented, namely (C12H30N4)Cs3BiI8 (CsBiI-1) and (C14H35N4)CsBiI7 (CsBiI-2), using different amines: C6H14N2 = cyclohexane-1,4-diamine (CDA) and C7H16N2 = 2-piperidinoethylamine (PDA). These two compounds show optical band gaps of 2.18 eV and 2.39 eV for CsBiI-1 and CsBiI-2, respectively. Both materials yield high surface coverage films from spin-coating. Moreover, CsBiI-1 and CsBiI-2 are stable under moisture and present photocurrent responses. Thus, these materials have the potential for use in light detection.

The halide perovskite Ruddlesden-Popper (RP) phases are a homologous layered subclass of solution-processable semiconductors that have aroused great attention, especially for developing long-term solar photovoltaics. They are defined as (A′)2(A)n-1PbnX3n+1 (A′ = spacer cation, A = cage cation, and X = halide anion). The orientation control of low-temperature self-assembled thin films is a fundamental issue associated with the ability to control the charge carrier transport perpendicular to the substrate. Here we report new chemical derivatives designed from a molecular perspective using a novel spacer cation 3-phenyl-2-propenammonium (PPA) with conjugated backbone as a low-temperature strategy to assemble more efficient solar cells. First, we solved and refined the crystal structures of single crystals with the general formula (PPA)2(FA0.5MA0.5)n-1PbnI3n+1 (n = 2 and 3, space group C2) using X-ray diffraction and then used the mixed halide (PPA)2(Cs0.05(FA0.88MA0.12)0.95)n-1Pbn(I0.88Br0.12)3n+1 analogues to achieve more efficient devices. While forming the RP phases, multiple hydrogen bonds between PPA and inorganic octahedra reinforce the layered structure. For films we observe that as the targeted layer thickness index increases from n = 2 to n = 4, a less horizontal preferred orientation of the inorganic layers is progressively realized along with an increased presence of high-n or 3D phases, with an improved flow of free charge carriers and vertical to substrate conductivity. Accordingly, we achieve an efficiency of 14.76% for planar p-i-n solar cells using PPA-RP perovskites, which retain 93.8 ± 0.25% efficiency with encapsulation after 600 h at 85 °C and 85% humidity (ISOS-D-3).

Deep-blue emitters are greatly desirable for preparing white light-emitting diodes and enhancing the color gamut of full-color display. The deep-blue lead halide perovskite light-emitting diodes (PeLEDs) exhibit far inferior performance compared to green and red counterparts and suffer from lead toxicity, hampering their applications. Nontoxic, stable, and wide band gap zero-dimensional (0D) Cs3Cu2I5 with relatively high exciton binding energy has great potential as deep-blue emitters. However, the development of PeLEDs remains a huge challenge due to the difficulties in preparing a high-quality Cs3Cu2I5 film and device design, arising from an inherent wide band gap together with deep ionization potential. Here, a continuous and pin-hole-free Cs3Cu2I5 thin film with deep-blue emission centered at 440 nm was prepared by the dual-source thermal evaporation approach, and a high photoluminescence quantum yield of 58% was achieved, corresponding to significant enhancement of 61% compared with that of the Cs3Cu2I5 thin film synthesized by solution processes. Furthermore, saturated deep-blue PeLEDs at the Commission Internationale de L'Eclairage (CIE) coordinates (0.15, 0.08) were obtained by employing an electron-transfer layer composed of a 1,4,5,8,9,11-hexa-azatriphenylene hexacarboni-trile (HAT-CN) and N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine (NPB) organic heterojunction to realize the effective hole blocking, rendering an external quantum efficiency of approximately 0.1%. These results will be extensively beneficial to wide band gap material and device preparation.

Low-toxicity tin-based perovskites have exhibited huge potential for photovoltaics applications. However, the facile oxidation of Sn2+ to Sn4+ induces ubiquitous Sn vacancies and p-type doping in p...

Blue-emitting materials and their light-emitting diodes (LEDs) are always challenging in lighting and display applications. Recently, perovskite LEDs (PeLEDs) with efficient and stable green/red em...

To best catch human eyes in next-generation displays, the updated recommendation 2020 (Rec. 2020) standard has called for ultrapure green emitters to be qualified with a narrow emission of 525-535 nm with a full width at half-maximum (fwhm) below 25 nm. However, it is still challenging to find an emitter which can simultaneously cover these two criteria. Instead of traditional II-VI group semiconductor quantum dots, perovskite nanocrystals (NCs) can render versatile emitting tunability to allow them access to the Rec. 2020 standard. Herein, to realize the critical window of Rec. 2020, we have proposed a scalable, room temperature synthesis route of formamidinium lead bromide (FAPbBr3) NCs using a sole ligand of sulfobetaine-18 (SBE-18). The as-synthesized FAPbBr3 NCs exhibit an ideal emission at 534 nm with an ultranarrow fwhm of 20.5 nm and a high photoluminescence quantum yield of 90.6%, overwhelming the FAPbBr3 nanoplates capped with oleic acid/oleylamine (OA/OAM). Introducing these high quality NCs into backlight displays, an ultrapure green backlight which covers ≈85.7% of the Rec. 2020 standard in the CIE 1931 color space is achieved, signifying the "greenest" backlight till now. Thus, we can foresee perovskite NCs as the most potential candidates for next-generation displays.

A series of 2-phenylpyridine (ppy)-type cyclometalating ligands containing rigid 5,9-dioxa-13b-boranaphtho[3,2,1-de]anthracene (OBA) units have been developed. Together with different ppy-type cyclometalating ligands with a phenylsulfonyl group (–SO2Ph) substituted at different positions, new unsymmetric heteroleptic cyclometalated Ir(III) complexes have been successfully synthesized. Their photophysical, electrochemical and electroluminescence (EL) behaviors have been fully characterized. In addition, both time-dependent functional theory (TD-DFT) and natural transition orbital (NTO) theoretical results have been obtained to gain insight into the optoelectronic behaviors of these unsymmetric Ir(III) complexes with OBA units. The NTO results indicate that the features of the lowest triplet excited states (T1) can be delicately tuned by combination between the OBA-based cyclometalating ligand and another ppy-type ligand with the –SO2Ph group. Importantly, these unsymmetric Ir(III) complexes can exhibit very high phosphorescence quantum yield (Φp) higher than 0.90 due to the highly rigid OBA unit which can effectively restrain non-radiative processes. In addition, an electron injection/transporting (EI/ET) ability can be conferred to these unsymmetric heteroleptic cyclometalated Ir(III) complexes by both OBA and –SO2Ph moieties. Taking advantage of these merits, organic light-emitting diodes (OLEDs) based on these unsymmetric heteroleptic cyclometalated Ir(III) complexes can show a high maximum external quantum efficiency (ηext) of 12.8%, a current efficiency (ηL) of 51.1 cd A−1, and a power efficiency (ηP) of 40.5 lm W−1 for a yellowish-green device, while EL efficiencies for red devices are 6.8%, 13.9 cd A−1, and 12.8 lm W−1, respectively. All these results indicate the good potential of the rigid OBA unit in developing functional phosphorescent emitters.

The toxicity of lead has inspired recent interest in making lead-free photovoltaic materials, among which the bimetallic double perovskite (DP) strategy is very promising. Unlike the popular Ag(I)–Bi(III) based DPs with wider band gaps ∼2.0 eV, in our previous study we found that the Cu(I)–Bi(III) method may have narrower band gaps ∼1.6 eV. Here we expand this strategy to various amines, from which we can see that the cyclic aliphatic amines (CAAs) are critical to govern the structural dimensions, thin film orientations and band gaps of the Cu(I)–Bi(III) iodide DPs. Among these compounds, CAAs with a “Z-shape” and six-member-rings result in two-dimensional structures (compounds 1–5), while CAAs with a “C-shape” and five-member-rings result in 1D bimetallic chains (compounds 6 and 7). Regardless of the structural dimensions, all seven compounds show narrow band gaps between 1.53 and 1.67 eV, which can be correlated to the distortions of the Cu–I–Bi angles. The band gap will be narrower if the Cu–I–Bi angle is closer to 180° or the octahedral distortion is smaller. Moreover, DFT calculations reveal that such band gaps are flat and direct in nature. Interestingly, the thin films formed by these compounds show preferential orientations to the ITO substrate with respect to the symmetries of the amines. For mirror-symmetric diamines the inorganic layers tend to be perpendicular to ITO; for asymmetric diamines the inorganic layers tend to be randomly oriented on ITO; for the asymmetric mono-amines the inorganic layers tend to be parallel to ITO. Such a phenomenon is, as far as we know, unknown to the field of perovskite thin film construction. To further reveal the potential of these materials for photovoltaic application we took compound 3 as a representative to study the photoelectric properties. From 20 °C to 130 °C, the conductivity of compound 3 increases over five orders of magnitude, ramping from 3.97 × 10−10 S cm−1 to 2.78 × 10−5 S cm−1, indicating a formal semiconducting behaviour. Thus, the photo-current response experiments show a ca. 17.5 nA difference between Ilight and Idark for 3, indicating the potential application of this material for light harvesting.

The energy level alignment and carrier mobility of the charge transport layer are of crucial importance for electron extraction and transport in planar heterojunction perovskite solar cells (PSCs). In this work, a carbon nitride modified SnO2 nanocomposite, SnO2/graphitic carbon nitride (g-C3N4) quantum dots, was designed as the functional electron transport layer (ETL) to precisely regulate the interfacial charge dynamics for high-performance PSCs. It is demonstrated that the g-C3N4 could recast the electronic density distribution around the neighboring SnO2 crystal unit, thus effectively eliminating the oxygen-vacancy-reduced trap centers and promoting the interface and bulk electron transport. Consequently, this carbon nitride modified SnO2 nanocomposite exhibits appropriate electrical properties including suitable energy level alignment and high conductivity. Employing the typical hybrid SnO2-based ETL, a maximum power conversion efficiency (PCE) of 22.13% (Voc = 1.176 V, Jsc = 24.03 mA cm−2, FF = 0.783) can be achieved for planar heterojunction PSCs, with negligible hysteresis and long-term stability (only 10% PCE decay after 1500 h at a relative humidity of 60%). Our work offers a hybrid ETL design strategy to improve the efficiency and stability of PSCs.

The environmental toxicity of lead may eventually hamper the wide applications of hybrid perovskite material-based solar cells despite their excellent power conversion efficiency. Here, we have used silver(I) and bismuth(III) to replace lead(II) and obtain two two-dimensional (2D) iodide-based double perovskites, (AMP)4[BiAgI8]2·H2O (1) and (APP)4[BiAgI8]·H2O (2), where AMP = 4-aminomethylpiperidine and APP = 4-aminopiperidine. Compared to our previously reported 1,4-cyclohexanediamine-based compound (C6H16N2)2[BiAgI8]·H2O with an indirect band gap, these two new 2D Ag–Bi double perovskites show direct band gaps (∼2.00 eV) due to the less distorted [AgI6] coordination geometry. Moreover, the photo-current response experiments showed a difference of more than 50 nA between light and dark conditions for both the compounds, indicating the potential application for light harvesting. 1 and 2 were also stable under heat and moisture. They showed high proton conductivity (∼10−4 S cm−1) at 95 °C and 90% RH. Thus, this work provides a new route for designing stable lead-free bimetallic iodide double perovskites with direct band gaps.

Deep traps originated from the defects formed at the surfaces and grain boundaries of the perovskite absorbers during their lattice assembly are the main reasons that cause nonradiative recombination and material degradation, which notably affect efficiency and stability of perovskite solar cells (PSCs). Here, we demonstrate the substantially improved PSC performance by capping the photoactive layer with low-dimensional (LD) perovskitoids. The undercoordinated Pb ions and metallic Pb at the surfaces of the three-dimensional (3D) perovskite are effectively passivated via the Pb-I bonding from the favorably lattice-matched 3D/LD interface. The good stability and hydrophobicity of the LD (0D and 1D) perovskitoids allow excellent protection of the 3D active layer under severe environmental conditions. The PSC exhibits a power conversion efficiency of 24.18%, reproduced in an accredited independent photovoltaic testing laboratory. The unencapsulated device maintains 90% of its initial efficiency after 800 hours of continuous illumination under maximum power point operating conditions.

Recently, perovskite light-emitting diodes (PeLEDs) have drew widespread attention due to their high efficiencies. However, because of the sensitivity to moisture and oxygen, perovskite luminescent layers are usually prepared in high-purity nitrogen environment, which increases the cost and process complexity of device preparation and seriously hindrances its commercialization of PeLED in lighting and display application. Herein, dual-phase all-inorganic composite CsPbBr3-Cs4PbBr6 films are fabricated from CsBr-rich perovskite solutions by a simple one-step spin-coating method in the air with high humidity. Compared with the pure CsPbBr3 film, the composite CsPbBr3-Cs4PbBr6 film has much stronger photoluminescence emission and longer fluorescence lifetime, accompanied by increased photoluminescence quantum yield (33%). As a result, we obtained green PeLED devices without hole transport layer exhibiting a maximum brightness of 72,082 cd/m2 and a maximum external quantum efficiency of about 2.45%, respectively. More importantly, the champion device shows excellent stability with operational half-lifetime exceeding 1,000 min under continuous operation in the air. The dual-phase all-inorganic composite CsPbBr3-Cs4PbBr6 film shows attractive prospect for advanced light emission applications.

The role of triplet states in the interfacial energy transfer in perovskite light-emitting diodes (PeLEDs) has so far not been clarified because of the complex exciton recombination and decay dynamics. This work aims to study this issue and accordingly proposes a novel interfacial-engineering strategy for efficient sky-blue PeLEDs. To this end, bis[2-(diphenylphosphino)phenyl]ether oxide with a high triplet energy level is introduced into sky-blue PeLEDs. It effectively reduces undesirable exciton transfer from the perovskite emission layer to the electron-transport layer, largely suppresses exciton quenching at the interface, and simultaneously passivates defects at the perovskite surfaces. As a result of the multichannel energy-loss reduction, sky-blue PeLED that emits at 488 nm is achieved with a peak external quantum efficiency of 10.17% and a maximum brightness of 6728.41 cd m-2. This work thus provides indirect evidence for the triplet mechanism of blue emission of mixed-halide perovskites and sheds new light on a promising way of boosting the performance of blue PeLEDs.

Utilization of triplet excitons, which generally emit poorly, is always fundamental to realize highly efficient organic light-emitting diodes (LEDs). While triplet harvest and energy transfer via electron exchange between triplet donor and acceptor are fully understood in doped organic phosphorescence and delayed fluorescence systems, the utilization and energy transfer of triplet excitons in quasi-two-dimensional (quasi-2D) perovskite are still ambiguous. Here, we use an orange-phosphorescence-emitting ultrathin organic layer to probe triplet behavior in the sky-blue-emitting quasi-2D perovskite. The delicate white LEDs architecture enables a carefully tailored Dexter-like energy-transfer mode that largely rescues the triplet excitons in quasi-2D perovskite. Our white organic-inorganic LEDs achieve maximum forward-viewing external quantum efficiency of 8.6% and luminance over 15000 cd m-2, exhibiting a significant efficiency enhancement versus the corresponding sky-blue perovskite LED (4.6%). The efficient management of energy transfer between excitons in quasi-2D perovskite and Frenkel excitons in organic layer opens the door to fully utilizing excitons for white organic-inorganic LEDs.

Interfaces between the perovskite active layer and the charge-transport layers (CTLs) play a critical role in both efficiency and stability of halide-perovskite photovoltaics. One of the major concerns is that surface defects of perovskite could cause detrimental nonradiative recombination and material degradation. In this work, we addressed this challenging problem by inserting ultrathin alkali-fluoride (AF) films between the tri-cation lead-iodide perovskite layer and both CTLs. This bilateral inorganic “walls” strategy makes use of both physical-blocking and chemical-anchoring functionalities of the continuous, uniform and compact AF framework: on the one hand, the uniformly distributed alkali-iodine coordination at the perovskite-AF interfaces effectively suppresses the formation of iodine-vacancy defects at the surfaces, thus reducing the trap-assisted recombination at the perovskite-CTL interfaces and therewith the open-voltage loss; on the other hand, the impermeable AF buffer layers effectively prevent the bidirectional ion migration at the perovskite-CTLs interfaces even under harsh working conditions. As a result, a power-conversion efficiency (PCE) of 22.02% (certified efficiency 20.4%) with low open-voltage deficit (

Layered Ruddlesden-Popper perovskite (RPP) photovoltaics have gained substantial attention owing to their excellent air stability. However, their photovoltaic performance is still limited by the unclear real-time charge-carrier mechanism of operating devices. Herein, we report the correlation between the charge-carrier mechanism and the spatially heterogeneous RPP bulks induced by distinct sublattice cations in the state-of-the-art antisolvent-driven RPP devices. In particular, abnormal heterogeneities ranging from the lateral long-range to local sub-grain scale and corresponding charge-carrier behaviours are visualized for triple-cation RPPs. We discovered that such heterogeneities with a unitary 2D/3D hybrid suppress lattice vibrations and reduce Fröhlich interactions by about 2 times, significantly promoting charge-carrier dynamics. Consequently, optimized triple-cation RPP solar cells greatly outperform their mono-cation counterparts. Furthermore, this principle can be applicable irrespective of 2D layer thickness (n > 2) and substrate type. This work provides a rationale for leveraging a disordered structure to stimulate charge-carrier motion and suggests the design principle of low-dimensional perovskites.