Achieving ultranarrow spectral linewidth and broad spectral tunability in light-emitting diodes (LEDs) remains challenging due to linewidth broadening from compositional and size heterogeneities. Here we report an interface-regulated vapour crystallization strategy that enables precise control over the spectral linewidth of solution-processed halide perovskite thin films. Underlying materials that exhibit minimal molecular interactions with perovskite precursors, exemplified by poly(9-vinylcarbazole), facilitate smooth ion diffusion and crystallization assisted by dimethylformamide vapour. This mechanism leads to perovskite films with both horizontal and vertical homogeneity and low inhomogeneous broadening comparable to that of perovskite single crystals. We demonstrate perovskite films with ultranarrow photoluminescence linewidths of 13.6 nm, 13.7 nm, 13.8 nm and 14.4 nm for emissions at 464 nm, 474 nm, 483 nm and 522 nm, respectively. This enables us to achieve sky-blue perovskite LEDs with narrow electroluminescence linewidths of 14.7 nm and a peak external quantum efficiency of 24.6%, with comparable linewidths and performance in LEDs spanning the pure blue to pure green. This work offers a practical and scalable strategy to realize narrow spectral linewidth, broad spectral tunability and high performance in thin film LEDs.

Traditional white light-emitting diodes operate by exciting phosphors using blue light-emitting diodes, leading to the absence of specific colour bands compared with the visible light region of the sunlight spectrum (400-780 nm), and excess blue light increases the risk of harmful effects on ecosystems and organisms. Here, we precisely design and regulate heterophase γ/δ-CsPb(I/Cl)3 at the nanoscale for uniform heterophase distribution, balanced flow of charges and tunable spectrum. Then, γ/δ-CsPb(I/Cl)3 directly excited by electricity shows full-spectrum white electroluminescence covering 400-780 nm with standard Commission Internationale de l'Eclairage coordinates of (0.33, 0.33), a Colour Rendering Index of 95, a Correlated Colour Temperature of 5829 K and a Delta u,v of -3 × 10-4, accompanied with balanced white light composition (Melanopic ratio = 1.004). The match indices of such five core indicators to standard sunlight reach 100%, 95% (97% for R9), 99.5%, 99.97% and 99.6%, respectively, far ahead of as-fabricated commercial white light-emitting diodes.

Colloidal quantum dots (QDs) have illuminated computer monitors and television screens due to their fascinating color-tunable properties depending on the size. Here, the electroluminescence (EL) wavelength of perovskite LEDs was tuned via the atomic layer number (ALN) of nanoplates (NPs) instead of the "size" in conventional QDs. We demonstrated efficient LEDs with controllably tailored emission from n = 3, 4, 5, and ≥7 ALN perovskite NPs with specific and discrete major peaks at 607, 638, 669, and 728 nanometers. These LEDs demonstrated peak external quantum efficiency (EQE) of 26.8% and high wavelength reproducibility with less than 1 to 2 nm difference between batches. High color stability without observable EL spectral change and operating stability with the best T50 of 267 minutes at 1.0 milliampere per square centimeter was also achieved. This work demonstrates a concept of tailoring specific ALN emission with fixed wavelengths, shedding light on efficient, emission-discrete, and color-stable LEDs for next-generation display.

Despite advances in p-i-n perovskite solar cells, interfacial losses between the electron transport layer (ETL) and metal electrode remain a bottleneck for efficiency and stability. Bathocuproine (BCP), a common buffer layer, suffers from poor film uniformity, low electron mobility, and limited thermal stability. Here, we report BTI-N, a D-A-D-type small molecule featuring a benzo-[c]-[1,2,5]-thiadiazole core and polar N,N-dimethylamino groups. BTI-N exhibits favorable molecular packing and solubility, enabling compact, uniform films with efficient electron transport. The polar termini anchor Ag electrodes via Ag-N dipole formation, lowering the work function and improving band alignment and charge extraction. BTI-N also suppresses Ag and I ion diffusion, significantly enhancing thermal stability. We demonstrate broad compatibility across ETLs (C60, PCBM), electrodes (Ag, Au), and perovskites with bandgaps from 1.58 to 1.7 eV. This work provides a practical interface engineering strategy to replace BCP and realize high-performance, stable perovskite solar cells.

The high optoelectronic quality of halide perovskites lends them to be utilized in optoelectronic devices and recently in emerging quantum emission applications. Advancements in perovskite nanomaterials have led to the discovery of processes in which luminescence decay times are sub-100 picoseconds, stimulating the exploration of even faster radiative rates for advanced quantum applications, which have only been prominently realised in III-V materials grown through costly epitaxial growth methods. Here, we discovered ultrafast quantum transients of time scales ~2 picoseconds at low temperature in bulk formamidinium lead iodide films grown through scalable solution or vapour approaches. Using a multimodal strategy, combining ultrafast spectroscopy, optical and electron microscopy, we show that these transients originate from quantum tunnelling in nanodomain superlattices. The outcome of the transient decays, photoluminescence, mirrors the photoabsorption of the states, with an ultra-narrow linewidth at low temperature as low as <2 nm (~4 meV). Localized correlation of the emission and structure reveals that the nanodomain superlattices are formed by alternating ordered layers of corner sharing and face sharing octahedra. This discovery opens new applications leveraging intrinsic quantum properties and demonstrates powerful multimodal approaches for quantum investigations.

An efficient n-dopant is essential to narrow the metal-organic energy barriers for efficient organic semiconductor optoelectronic devices. Molecular n-dopants feature clear merits of versatile molecular manipulation. However, few can achieve ohmic electron contact due to deficient design strategies. Recent studies have revealed that incorporating strong electron-donating groups (EDGs) not only helps to increase the nucleophilicities and reduce electron affinities of n-dopants, but also facilitates an efficient electron-transfer process by stabilizing the resulting carbocations, thus enabling high n-doping efficiency. A comprehensive review elucidating the underlying physics is imperative for a thorough understanding of how to tune the EDGs precisely, motivating more effective design strategies. Herein, we highlight the conjugative effect as a promising design paradigm for potent n-dopants. This perspective delves into the fundamental principles and latest progress relating to the conjugative effect, culminating in a prospective outlook on the future design strategy of molecular n-dopants for high-performance organic optoelectronics.

Developing an additive to effectively regulate the perovskite crystallization kinetics for the optimized optoelectronic properties of perovskite film plays a vital role in obtaining high efficiency and stable perovskite solar cells (PSCs). Herein, a new additive is designed and directly synthesized in perovskite precursor solution by utilizing an addition reaction between but-3-yn-1-amine hydrochloride (BAH) and formamidinium iodide. It is found that its product may control the intermediate precursor phase for regulating perovskite nucleation, leading to advantageous 2D perovskite to induce growth of perovskite along the preferred [001] orientation with not only released lattice strain but also strong interaction with perovskite to passivate its surface defects. By taking advantage of the above synergistic effects, the optimized PSC delivers an efficiency of 25.19% and a high open-circuit voltage (VOC) of 1.22 V. Additionally, the devices demonstrate good stability, remaining over 90% of their initial efficiencies under ambient atmosphere conditions for 60 days, high temperature of 85 °C for 200 h, or maximum power point tracking for 500 h.

AbstractThermoelectrics converting heat and electricity directly attract broad attentions. To enhance the thermoelectric figure of merit, zT, one of the key points is to decouple the carrier-phonon transport. Here, we propose an entropy engineering strategy to realize the carrier-phonon decoupling in the typical SrTiO3-based perovskite thermoelectrics. By high-entropy design, the lattice thermal conductivity could be reduced nearly to the amorphous limit, 1.25 W m−1 K−1. Simultaneously, entropy engineering can tune the Ti displacement, improving the weighted mobility to 65 cm2 V−1 s−1. Such carrier-phonon decoupling behaviors enable the greatly enhanced μW/κL of ~5.2 × 103 cm3 K J−1 V−1. The measured maximum zT of 0.24 at 488 K and the estimated zT of ~0.8 at 1173 K in (Sr0.2Ba0.2Ca0.2Pb0.2La0.2)TiO3 film are among the best of n-type thermoelectric oxides. These results reveal that the entropy engineering may be a promising strategy to decouple the carrier-phonon transport and achieve higher zT in thermoelectrics.

Judicious tailoring of the interface between the SnO2 electron-transport layer and the perovskite buried surface plays a pivotal role in obtaining highly efficient and stable perovskite solar cells (PSCs). Herein, a DL-carnitine hydrochloride (DL) is incorporated into the perovskite/SnO2 interface to suppress the defect-states density. A DL-dimer is obtained at the interface by an intermolecular esterification reaction. For the SnO2 film, the Cl- in the DL-dimer can passivate oxygen vacancies (VO ) through electrostatic coupling, while the N in the DL-dimer can coordinate with the Sn4+ to passivate Sn-related defects. For the perovskite film, the DL-dimer can passivate FA+ defects via hydrogen bonding and Pb-related defects more efficiently than the DL monomer. Upon DL-dimer modification, the interfacial defects are effectively passivated and the quality of the resultant perovskite film is improved. As a result, the DL-treated device achieves a gratifying open-circuit voltage (VOC ) of 1.20 V and a champion power conversion efficiency (PCE) of 25.24%, which is a record value among all the reported FACsPbI3 PSCs to date. In addition, the unencapsulated devices exhibit a charming stability, sustaining 99.20% and 90.00% of their initial PCEs after aging in air for 1200 h and continuously operating at the maximum power point tracking for 500 h, respectively.

Organic-inorganic hybrid perovskite solar cells (PSCs) have been extensively researched as a promising photovoltaic technology, wherein the orientation of the perovskite film plays a crucial role in the power conversion efficiency (PCE) and stability. Here, a seed-mediated method is developed to in situ grow a layer of 2D perovskite seed for epitaxial growth of 3D perovskite atop it to construct a high-quality 2D/3D heterojunction. It is found that the epitaxial 3D perovskite film exhibits a preferred [112] direction, which is different from traditional perovskites with a preferred [001] orientation. The oriented perovskite film consists of large-sized grains with low defect density, long charge-carrier lifetime, and good stability, resulting in efficient PSCs with a champion efficiency of 24.83%. In addition, the devices exhibit high stability under ambient, thermal, and continuous light-soaking conditions. This work provides an effective strategy for achieving high-quality perovskite films with tunable orientation to simultaneously boost the efficiency and stability of PSCs.

Surmounting complicated defects at the electron transport layer (ETL) and perovskite interface plays a non‐trivial role in improving efficiency and stability of perovskite solar cells (PSCs). Herein, an asymmetric interface modification strategy (AIMS) is developed to passivate the defects from both a SnO 2 ETL and the perovskite buried surface via incorporating 1,3‐thiazole‐2,4‐diammonium (TDA) into the SnO 2 /perovskite interface. Detailed experimental and calculated results demonstrate that N3 (the nitrogen atom bonding to the imine) in the TDA preferentially cures the free hydroxyl (OH), oxygen vacancy ( V O ), and the Sn‐related defects on the SnO 2 surface, while N1 (the nitrogen atom bonding to the vinyl) is more inclined to passivate the Pb 2+ and I − related defects at the perovskite buried surface. As a result, the TDA‐modified FACsPbI 3 PSC yields a champion power conversion efficiency (PCE) of 24.96% with a gratifying open‐circuit voltage ( V oc ) of 1.20 V. In addition, the optimized PSCs exhibit charming air‐operational stability with the unencapsulated device sustaining 97.04% of its initial PCE after storage in air conditions for 1400 h. The encapsulated device maintains 90.21% of its initial PCE after maximum power point tracking for 500 h.

The improvement of power conversion efficiency (PCE) and stability of the perovskite solar cell (PSC) is hindered by carrier recombination originating from the defects at the buried interface of the PSC. It is crucial to suppress the nonradiative recombination and facilitate carrier transfer in PSC via interface engineering. Herein, P-biguanylbenzoic acid hydrochloride (PBGH) is developed to modify the tin oxide (SnO2)/perovskite interface. The effects of PBGH on carrier transportation, perovskite growth, defect passivation, and PSC performance are systematically investigated. On the one hand, the PBGH can effectively passivate the trap states of Sn dangling bonds and O vacancies on the SnO2 surface via Lewis acid/base coordination, which is conducive to improving the conductivity of SnO2 film and accelerating the electron extraction. On the other hand, PBGH modification assists the formation of high-quality perovskite film with low defect density due to its strong interaction with PbI2. Consequently, the PBGH-modified PSC exhibits a champion power conversion efficiency (PCE) of 24.79%, which is one of the highest PCEs among all the FACsPbI(3)-based PSCs reported to date. In addition, the stabilities of perovskite films and devices under high temperature/humidity and light illumination conditions are also systematically studied.

High density of defects at interface severely affects the performance of perovskite solar cells (PSCs). Herein, cobalt (II) hexafluoro‐2,4‐pentanedionat (CoFAc), a hinge‐type fluorine‐rich complex, is introduced onto the surface of formamidinium cesium lead iodide (FACsPbI 3 ) film to address the issues of perovskite/Spiro‐OMeTAD interface. The existence of CoFAc passivates both organic cation and halide anion vacancies by establishing powerful hydrogen bonds with HC(NH 2 ) 2 + (FA + ) and strong ionic bonds with Pb 2+ in perovskite films. In addition, CoFAc serves as a connecting link to enhance interfacial hole‐transport kinetics via interacting with Spiro‐OMeTAD. Consequently, FACsPbI 3 PSCs with CoFAc modification display a champion power conversion efficiency (PCE) of 24.64% with a charming open‐circuit voltage ( V OC ) of 1.191 V, which is the record V OC among all the reported organic‐inorganic hybrid PSCs with TiO 2 as electron transport layer. Furthermore, CoFAc‐modified devices exhibit an outstanding long‐term stability, which can maintain 95% of their initial PCEs after exposure to ambient atmosphere for 1500 h without any encapsulation.

The poor interface quality between cesium lead triiodide (CsPbI 3 ) perovskite and the electron transport layer limits the stability and efficiency of CsPbI 3 perovskite solar cells (PSCs). Herein, a 4‐amino‐2,3,5,6‐tetrafluorobenzoate cesium (ATFC) is designed as a bifacial defect passivator to tailor the perovskite/TiO 2 interface. The comprehensive experiments demonstrate that ATFC can not only optimize the conductivity, electron mobility, and energy band structure of the TiO 2 layer by passivation of the undercoordinated Ti 4+ , oxygen vacancy ( V O ), and free OH defects but also promote the yield of high‐quality CsPbI 3 film by synergistic passivation of undercoordinated Pb 2+ defects with the CO group and F atom, and limiting I − migration via F···I interaction. Benefiting from the above interactions, the ATFC‐modified CsPbI 3 device yields a champion power conversion efficiency (PCE) of 21.11% and an excellent open‐circuit voltage ( V OC ) of 1.24 V. Meanwhile, the optimized CsPbI 3 PSC maintains 92.74% of its initial efficiency after aging 800 h in air atmosphere, and has almost no efficiency attenuation after tracking at maximum power point for 350 h.

Formamidinium methylammonium lead iodide (FAMAPbI3) perovskite has been intensively investigated as a potential photovoltaic material because it has higher phase stability than its pure FAPbI3 perovskite counterpart. However, its power conversion efficiency (PCE) is significantly inferior due to its high density of surface detects and mismatched energy level with electrodes. Herein, a bifunctional passivator, methyl haloacetate (methyl chloroacetate, (MClA), methyl bromoacetate (MBrA)), is designed to reduce defect density, to tune the energy levels and to improve interfacial charge extraction in the FAMAPbI3 perovskite cell by synergistic passivation of both CO groups and halogen anions. As predicted by modeling undercoordinated Pb2+, the MBrA shows a very strong interaction with Pb2+ by forming a dimer complex ([C6H10Br2O4Pb]2+), which effectively reduces the defect density of the perovskite and suppresses non‐radiative recombination. Meanwhile, the Br− in MBrA passivates iodine‐deficient defects. Consequently, the MBrA‐modified device presents an excellent PCE of 24.29%, an open‐circuit voltage (Voc) of 1.18 V (Voc loss ≈ 0.38 V), which is one of the highest PCEs among all FAMAPbI3‐based perovskite solar cells reported to date. Furthermore, the MBrA‐modified devices without any encapsulation exhibit remarkable long‐term stability with only 9% of PCE loss after exposure to ambient air for 1440 h.

Flexible perovskite solar cells (f-PSCs) have attracted great attention because of their unique advantages in lightweight and portable electronics applications. However, their efficiencies are far inferior to those of their rigid counterparts. Herein, a novel histamine diiodate (HADI) is designed based on theoretical study to modify the SnO2 /perovskite interface. Systematic experimental results reveal that the HADI serves effectively as a multifunctional agent mainly in three aspects: 1) surface modification to realign the SnO2 conduction band upward to improve interfacial charge extraction; 2) passivating the buried perovskite surface, and 3) bridging between the SnO2 and perovskite layers for effective charge transfer. Consequently, the rigid MA-free PSCs based on the HADI-SnO2 electron transport layer (ETL) display not only a high champion power conversion efficiency (PCE) of 24.79% and open-circuit voltage (VOC ) of 1.20 V but also outstanding stability as demonstrated by the PSCs preserving 91% of their initial efficiencies after being exposed to ambient atmosphere for 1200 h without any encapsulation. Furthermore, the solution-processed HADI-SnO2 ETL formed at low temperature (100 °C) is utilized in f-PSCs that achieve a PCE as high as 22.44%, the highest reported PCE for f-PSCs to date.

Suppressing defects at the interface between the TiO2 electron transport layer (ETL) and perovskite film is critical for high efficiency and stable perovskite solar cells (PSCs). Herein, a siloxane derivative diethylphosphatoethylsilicic acid (PSiOH) is developed to modify the interface of TiO2 ETL/FA0.83 Cs0.17 PbI3 perovskite. Comprehensive characteristics reveal that silicon hydroxyl (SiOH) in PSiOH can reduce surface defects, improve the electrical properties and optimize the energy band structure of TiO2 by forming a SiOTi bond, while the phosphate bond (PO) in PSiOH can passivate Pb-related defects on the perovskite bottom surface. Consequently, PSiOH-modified PSCs yield a remarkable power conversation efficiency of 24.20% and improved air, thermal, or illumination stabilities. This study provides insight into passivation defects at the buried interface for efficient and stable PSCs.

There are many grain boundaries and defects in polycrystalline perovskite films, resulting in sacrificed efficiency and instability for perovskite solar cells (PSCs). By regulating the growth of perovskite grains along the vertical direction through epitaxial growth, one may expect fewer grain-boundaries, effective charge transport, improved crystalline quality, and reduced defect density. However, there is still no suitable epitaxial growth substrate for perovskite. Here, we developed an electrochemical lithiation intercalation and ultrasonication method to prepare high-quality antimonene nanosheets (ANs). It is found that the perovskite film grows preferentially along the (012) planes of the ANs that have perfect lattice match with the (001) planes of the perovskite, leading to a high-quality perovskite film with a preferential orientation along the [001] direction and greatly enlarged grain size. Consequently, the oriented perovskite-based PSC achieves a remarkable PCE of 24.54% and shows an enhanced stability under ambient conditions, thermal annealing or light illumination. This work opens an effective avenue to effectively control the oriented growth of perovskite film for high-performance perovskite optoelectrical devices.

An ideal host for blue emitters with thermally activated delayed fluorescence (TADF) should bear a moderate polarity to relax charge transfer (CT) states of dopant for a reduced singlet-triplet energy gap (Delta E-ST) while uttermostly keeping blue emission, a high triplet energy to confine exciton, and a small Delta E-ST for feasible charge injection. However, it is rather challenging to simultaneously fulfill all those requirements as the strong CT characteristic necessary for a small Delta E-ST usually enlarge polarity and lower energy levels. Here, a symmetrical ortho-linked diphenylphosphine oxide (DPO)/carbazole derivative is developed, of which the configuration resembles the bee with carbazoles as front wings, phenyl rings on DPO as back wings, hooked together by pi-pi interaction. This motif features a short distance of charges for a moderate polarity of 3.45 D, a twisted nonconjugation structure for a small Delta E-ST of 0.24 eV with a high triplet of 2.98 eV and multiple intermolecular interactions for enhanced charge transport. The corresponding blue TADF device realizes a compromise between efficiency and colors with a maximum external quantum efficiency (EQE(max)) of 35.7% and a CIEy of 0.20. Furthermore, a full-TADF white device with this host realizes a EQE(max) of 26.1%, representing the state-of-the art performance.

Organic-inorganic halide perovskites have become promising materials for the next generation of photovoltaic devices on account of the preeminent optoelectronic characteristics and boundless potentialities. Perovskite solar cells (PSCs) normally require a complex structure design with an electron transport layer (ETL) to provide a builtin electric field and depress the probability of carrier recombination. Nonetheless, the construction of a proper ETL is not cost-effective, which precludes the practical commercialization of the PSCs. In this respect, a simplified ETL-free PSC is successfully fabricated by inserting a facile and efficient 1-[N-(2-Hydroxyethyl)-4 '-piperidyl]-3(4 '-piperidyl) propane (PPPDE) small-molecule thin interlayer between the FTO substrate and perovskite film. Compared with the bare FTO-based PSCs, this surface engineering can prominently ameliorate the photovoltaic performance parameters, yielding an extraordinary PCE of up to 19.71% with a ca. 31% efficiency enhancement, which can be attributed to the optimized interface energy-level alignment with a barrier-free contact, the elevated charge transfer and collection as well as the suppressed electron-holes recombination at the FTO/ perovskite interface. Synchronously, the long-term air stability is also improved with mitigated J-V hysteretic behavior due to the larger grain size of perovskite and the suppressed defect-induced degradation. Furthermore, an augmented performance of 15.87% was achieved for the flexible PPPDE embedded ETL-free PSC fabricated on ITO/PEN substrates via a low-temperature deposition process. The demonstrated PPPDE interlayer presents a brand-new strategy that can simplify the cell configuration and improve the photovoltaic performance of ETLfree PSCs.