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The threshold carrier density, conventionally evaluated from optical pumping, is a key reference parameter towards electrically pumped lasers with the widely acknowledged assumption that optically excited charge carriers relax to the band edge through an ultrafast process. However, the characteristically slow carrier cooling in perovskites challenges this assumption. Here, we investigate the optical pumping of state-of-the-art bromide- and iodine-based perovskites. We find that the threshold decreases by one order of magnitude with decreasing excitation energy from 3.10 eV to 2.48 eV for methylammonium lead bromide perovskite (MAPbBr(3)), indicating that the low-energy photon excitation facilitates faster cooling and hence enables efficient carrier accumulation for population inversion. Our results are then interpreted due to the coupling of phonon scattering in connection with the band structure of perovskites. This effect is further verified in the two-photon pumping process, where the carriers relax to the band edge with a smaller difference in phonon momentum that speeds up the carrier cooling process. Furthermore, by extrapolating the optical pumping threshold to the band edge excitation as an analog of the electrical carrier injection to the perovskite, we obtain a critical threshold carrier density of similar to 1.9 x 10(17) cm(-3), which is one order of magnitude lower than that estimated from the conventional approach. Our work thus highlights the feasibility of metal halide perovskites for electrically pumped lasers. Funding Agencies|ERC Consolidator Grant [101045098]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]; China National Key Basic Research Program [2022YFA1404800]; National Science Foundation of China [12234007, 12221004, 91963212]; Science and Technology Commission of Shanghai Municipality [19XD1434600, 2019SHZDZX01, 19DZ225 3000, 20501110500, 21DZ1101500]; Marie Curie Fellowship [Horizon-MSCA-2021-PF, 101066960]; Horizon Europe

With the development of perovskite photodetectors, integrating photodetectors into array image sensors is the next target to pursue. The major obstacle to integrating perovskite photodiodes for dynamic imaging is the optoelectrical crosstalk among the pixels. Herein, a perovskite photodiode-blocking diode (PIN-BD) crossbar array with pixel-wise rectifying property by the vapor deposition method is presented. The PIN-BD shows a large rectification ratio of 3.3 × 10

The device stability and toxic-solvent-free processing are indispensable development to industrialize organometal halide perovskite solar cells. In this work, the conventional top surface of vapor prepared 3D-MAPbI3 was replaced by 2D-(BA)2(MA)n‐1PbnI3n+1 perovskite platelet via molecular substitution from MA (CH3NH) to BA (C4H9NH2). Our fully vapor process fabricated a 3D-2D perovskite heterojunction for solar cell application, realizing the power conversion efficiency as high as 16.50% and the average one as 15.40%. Furthermore, unencapsulated devices can sustain their 81% efficiency after 30 days under 55% RH, and also 74% efficiency after 30 days under 80 °C heat stress. Stability of humidity resistance arises from the reduced n value of 2D perovskite caused by the surface reaction of moisture, and the improvement of thermal stability comes from the buffering of MA molecules release. Meanwhile, the fabrication of large scale device with high efficiency is also demonstrated in our experiment.

Long-term stability of organic-inorganic hybrid perovskite solar cells (PSCs) is inhibited by ion diffusion. Herein, we introduce a thermally stable and hydrophobic silicone resin layer with a network structure as an interfacial layer between the perovskite and the hole-transporting layer (HTL). Experimental and theoretical investigations confirm that the small Si-O-Si unit in the network forms both Si-I and Pb-O bonds with the perovskite surface, which physically and chemically inhibit the diffusion and self-release of iodine. Besides, the silicone resin layer suppresses the thermal crystallization of spiro-OMeTAD and optimizes the interfacial energy level alignment for hole extraction. The power conversion efficiency (PCE) of a perovskite solar cell with a silicone resin layer is improved to 21.11%. The device maintains more than 90.1% of its original PCE after 1200 h under 85 °C thermal stress, 99.6% after 2000 h under RH ∼55 ± 5%, and 83% of its original PCE after light soaking in air for 1037 h.

Bandgap tuning through mixing halide anions is one of the most attractive features for metal halide perovskites. However, mixed halide perovskites usually suffer from phase segregation under electrical biases. Herein, we obtain high-performance and color-stable blue perovskite LEDs (PeLEDs) based on mixed bromide/ chloride three-dimensional (3D) structures. We demonstrate that the color instability of CsPb(Br1-xClx)(3) PeLEDs results from surface defects at perovskite grain boundaries. By effective defect passivation, we achieve color-stable blue electroluminescence from CsPb(Br1-xClx)(3) PeLEDs, with maximum external quantum efficiencies of up to 4.5% and high luminance of up to 5351 cd m(-2) in the sky-blue region (489 nm). Our work provides new insights into the color instability issue of mixed halide perovskites and can spur new development of high-performance and color-stable blue PeLEDs. Funding Agencies|ERC Starting GrantEuropean Research Council (ERC) [717026]; Swedish Energy Agency EnergimyndighetenSwedish Energy Agency [48758-1, 44651-1]; Swedish Foundation for International Cooperation in Research and Higher Education [CH2018-7736]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [200900971]; China Scholarship CouncilChina Scholarship Council

All-inorganic perovskite CsPbI2Br usually requires a high fabrication temperature (higher than 200 °C) and suffers from an unwanted phase transition from a photo-active cubic phase to a photo-inactive orthorhombic phase. Here, we demonstrate an effective anti-solvent-free route to simultaneously stabilize the cubic phase and lower the fabrication temperature of perovskite solar cells with guanidinium (GA) cation doping. It is suggested that a trace amount of GA in the precursor could enter the substitutional sites to stabilize the cubic phase by relaxing the lattice strain and forming strong hydrogen bonds. State-of-the-art in situ grazing-incidence wide-angle X-ray scattering (GIWAXS) measurements reveal that GA could advance the crystallization of the cubic phase, indicating that the formation of the perovskite cubic phase experiences a lowered energy barrier with the assistance of GA, thereby resulting in a significant decrease of the fabrication temperature. An efficiency as high as 14.34% was achieved at a low fabrication temperature of 140 °C. With the help of GA, the device maintains ∼94% of its initial efficiency after being stored for 1000 h.

Vapor reaction is one of the major methods used for large-scale fabrication of high-quality organic–inorganic halide perovskite solar cells, but its detailed process is rarely investigated. In this study, the thermal and illumination effects on PbI2 and its transformation to CH3NH3PbI3 (MAPbI3) under CH3NH3I (MAI) vapor were investigated. Atomic shifting of the PbI2 layer was observed, which caused the generation of defects and distortion in PbI2 without breaking the phase structure. The reaction with MAI started with decoupling of PbI2 layers and formation of nanoislands and then, the transformation of PbI2 to MAPbI3 proceeded randomly on the surface from top to bottom. Additional illumination of the reaction suppressed the transformation, causing the generation of PbI2 nano-walls along [100] and [010] directions, leading to decrease in power conversion efficiency.

Surface passivation has played a critical role for efficient and stable perovskite solar cells by reducing surface defects, promoting charge transport, and preventing the penetration of degrading agents. State-of-the-art passivation approaches mainly rely on the formation of a two-dimensional (2D) perovskite layer or the deposition of an ultrathin layer based on the molecular design. Here, we demonstrated a novel nanocrystal-pinning passivation by dripping 2-bromoethyltrimethylammonium bromide (BETAB) colloidal solution onto perovskite films. Theoretical simulation and kinds of experimental results confirm that BETAB nanocrystals can effectively reduce the defect density of perovskite films. Impressively, the resulting FA1-xMAxPbI3 based planar devices exhibit a champion power conversion efficiency (PCE) of 23.04% (certified: 22.10%) with a voltage loss of only 390 mV. Besides, the BETAB nanocrystals could simultaneously increase the hydrophobic property of perovskite films and prevent the reaction and formation of 2D perovskites during device operation. Correspondingly, the resulted devices exhibit excellent stability under moisture, heating, and operational tracking conditions.

MAPbI 3 perovskite is an important component for high-performance perovskite solar cell (PSC) but its own thin film stability is challenging in PSC community. Herein, we report a high crystallinity perovskite MAPbI 3 with texture structure prepared from HPbI 3 reacted with low partial pressure (LPP) MA gas, that has substantially higher both thermal and moisture stability than polycrystalline perovskite (PP) prepared from MAI+PbI 2 . A prototype reactor is developed to perform coordination engineering between MA vapor and HPbI 3 solid and facilitate the large-scale fabrication. The large Pb-N binding energy (~80.04 kJ mol −1 ) results in the liquefied state after MA adhesion. Finally, a high texture perovskite (TP) is formed after excess MA expeditious releasing. The MA-rich passivation through Pb-N bonding at interface and boundary contributes to the substantial improved stability. Besides, MA-rich species trigger an anti-degradation reaction in presence of moisture and thus endow stability above two months under ~65% humidity. The textured PSCs (TPSCs) deliver power conversion efficiency (PCE) between 15.5% and champion 18.9% in the batch deposition. Therefore, the coordination engineering improves the efficiency, stability, scalability and ease of fabrication together.

Defects engineering can broaden the absorption band of wide band gap van der Waals (vdW) materials to the visible or near-IR regime at the expense of material stability and photoresponse speed. Herein, we introduce an atomic intercalation method that brings the wide band gap vdW α-MoO3 for vis–MIR broadband optoelectronic conversion. We confirm experimentally that intercalation significantly enhances photoabsorption and electrical conductivity buts effects negligible change to the lattice structure as compared with ion intercalation. Charge transfer from the Sn atom to the lattices induces an optoelectrical change. As a result, the Sn-intercalated α-MoO3 shows room temperature, air stable, broadband photodetection ability from 405 nm to 10 μm, with photoresponsivity better than 9.0 A W–1 in 405–1500 nm, ∼0.4 A W–1 at 3700 nm, and 0.16 A W–1 at 10 μm, response time of ∼0.1 s, and peak D* of 7.3 × 107 cm Hz0.5 W–1 at 520 nm. We further reveal that photothermal effect dominates in our detection range by real...

Dimension regulation and defect passivation are two key strategies for highly efficient and stable perovskite solar cell. Vapor deposition of perovskite is a toxic-solvent-free method for large-scale fabrication. However, without the assistance of solvent for crystal optimization, effective structural regulation and defect passivation become challenging. Here, detailed investigations on the structural evolution of perovskite thin film are carried out in sequential vapor deposition using mixed-vapor (R-NH3I/MAI). Correlation between electron donating ability of R-NH3I (BAI, PEAI, PMAI and ALI) molecule and the way of structural transition is established. It is found that R-NH3I with stronger electron-donating ability promoted the phase transition from three-dimensional (3D) to two-dimensional (2D) perovskite. Typically, the n value from 1 to 5 can be tuned by reaction time or component control using BAI with the strongest electron donating ability. R-NH3I with weak electron-donating ability suppresses the 3D to 2D transition, but enhances the defect passivation effect. The ALI with the weakest electron donating ability shows the best passivation effect, leading to the best device performance than that of the control 3D device, with PCE of 18.23% (0.045 cm2) and 15.48% (1 cm2) and the significantly improved stability. This study provides the evidence that the concept of Lewis acid-base reaction is applicable in vapor deposition, which provides us with the selection guide of R-NH3I molecules for structural design in vapor fabrication of perovskite thin film.

Quantification of intergrain length scale properties of CH3NH3PbI3 (MAPbI3) can provide further understanding of material physics, leading to improved device performance. In this work, we noticed that two typical types of facets appear in sequential deposited perovskite (SDP) films: smooth and steplike morphologies. By mapping the surface potential as well as the photoluminescence (PL) peak position, we revealed the heterogeneity of SDP thin films that smooth facets are almost intrinsic with a PL peak at 775 nm, while the steplike facets are p-type-doped with 5-nm blue-shifted PL peak. Considering the reaction process, we propose that the smooth facets have well-defined crystal lattices that resulted from the interfacial reaction between MAI and PbI2 domains containing low trap states density. The steplike facets are MAI-rich originated from the grain boundaries of PbI2 film and own more trap states. Conversion of steplike facets to smooth facets can be controlled by increasing the reaction time through O...

High quality polycrystalline CH3NH3PbI3 was prepared by dripping the γ-butyrolactone (GBL) solution of CH3NH3PbI3 into toluene, dimethylformamide (DMF) and dimethylsilicone oil. In toluene, a compact CH3NH3PbI3 thin film was observed but with grain size smaller than 1 μm because of the rapid extraction of GBL. As CH3NH3PbI3 is soluble in DMF, the crystallization in DMF is understood by interdiffusion induced local and temporal supersaturated droplets, which allow for growth of irregular, separated single crystals with size of more than 0.1 mm. In dimethylsilicone oil, compact, yolk-like polycrystalline CH3NH3PbI3 was observed. Unlike the round grains observed in toluene, it is composed of single crystal grains with clear angular surfaces. The average crystal size is tens of μm and can be modulated by the solvent temperature. We suggest that the poor miscibility between GBL and dimethylsilicone oil, and the poor solubility of CH3NH3I, PbI2 and CH3NH3PbI3 in the dimethylsilicone oil, allow slow extraction of GBL while keeping the stoichiometry of CH3NH3PbI3. The results offer a feasible and high-yielding method for growing uniform CH3NH3PbI3 crystals in a few seconds.

Directional optical nanoantennas are often realized by nanostructured systems with ingenious or complex designs. Herein we report on the realization of directional scattering of visible light from a simple configuration made of single Ag nanorods supported on Si substrates, where the incident light can be routed toward the two flanks of each nanorod. Such an intriguing far-field scattering behavior, which has not been investigated so far, is proved to result from the near-field coupling between high-aspect-ratio Ag nanorods and high-refractive-index Si substrates. A simple and intuitive model is proposed, where the complicated plasmon resonance is found to be equivalent to several vertically aligned electric dipoles oscillating in phase, to understand the far-field properties of the system. The interference among the electric dipoles results in wavefront reshaping and sidewise light routing in a similar manner to the broadside antenna described in the traditional antenna theory, allowing for the naming of these Si-supported Ag nanorods as "broadside nanoantennas". We have carried out comprehensive experiments to understand the physical origins behind and the affecting factors on the directional scattering behavior of such broadside nanoantennas.

The mixed cation lead mixed halide perovskite (MLMP) Csx FA1-x PbIy Br3-y is one of the most promising candidates for both single-junction and tandem solar cells due to its high efficiency and remarkable stability. However, the composition effect on thermal stability and photovoltaic performances has not yet been comprehensively investigated. Therefore, the interplay between composition, crystal structure, morphology, and optoelectronic properties under heat stress, is systematically elucidated here through a series of in situ characterizations. It is revealed for the first time that the FA+ and Br- release synchronously at first even under mild annealing. This leads to a serious FA- and Br-deficiency issue, with only 88.3% of Br and 90.2% of FA retained after annealing at 100 °C, which significantly magnifies the hysteresis, phase segregation, and instability issues. Finally, a trace amount of FA+ and Br- is introduced onto the post-annealed MLMP surface to compensate for the deficiency through vacancy filling. The degradation lifetime to 80% of the initial efficiency (t80 ) is improved from 504 to 1056 h and the hysteresis issue is also well resolved. This work highlights the importance of the synergetic composition effect of the organic cation and halide anion on stability and efficiency optimization for long-term applications.

We developed a molecule/polymer composite hole transporting material (HTM) with a periodic microstructure for morphology replication of a corrugated Au electrode, which in combination plays a dual role in the optical and electronic enhancement of high performance perovskite solar cells (PSCs). The electro-optics revealed that perovskite couldn't readily extinct the red light even though the thickness increased to 370 nm, but we found that the quasi periodic microstructure composite (PMC) HTM in combination with the conformal Au electrode could promote the absorption through the enhanced cavity effects, leading to comparable absorption even using much thinner perovskite (240 nm). We identified that the cavity was the combination of Fabry-Pérot interferometer and surface plasmonic resonance, with light harvesting enhancement through surface plasmon polariton or waveguide modes that propagate in the plane of the perovskite layer. On the other hand, the PMC HTM increased hole conductivity by one order of magnitude with respect to standard spiro-OMeTAD HTM due to molecular packing and self-assembly, embodying traceable hole mobility and density elevation up to 3 times, and thus the hysteresis was greatly avoided. Owing to dual optical and electronic enhancement, the PMC PSC afforded high efficiency PSC using as thin as 240 nm perovskite layer, delivering a V(oc) of 1.05 V, J(sc) of 22.9 mA cm(-2), FF of 0.736, and efficiency amounting to 17.7% PCE, the highest efficiency with ultrathin perovskite layer.

The mixed perovskite (FAPbI3)1−x(MAPbBr3)x, prepared by directly mixing different perovskite components, suffers from phase competition and a low-crystallinity character, resulting in instability, despite the high efficiency. In this study, a dual ion exchange (DIE) method is developed by treating as-prepared FAPbI3 with methylammonium brodide (MABr)/tert-butanol solution. The converted perovskite thin film shows an optimized absorption edge at 800 nm after reaction time control, and the high crystallinity can be preserved after MABr incorporation. More importantly, it is found that the threshold electrical field to initiate ion migration is greatly increased in DIE perovskite thin film because excess MABr on the surface can effectively heal structural defects located on grain boundaries during the ion exchange process. It contributes to the over-one-month moisture stability under ≈65% room humidity (RH) and greatly enhanced light stability for the bare perovskite film. As a result of preserved high crystallinity and simultaneous grain boundary passivation, the perovskite solar cells fabricated by the DIE method demonstrate reliable reproducibility with an average power conversion efficiency (PCE) of 17% and a maximum PCE of 18.1%, with negligible hysteresis.