Search

The development of natural polymer-based hydrogels, combining outstanding injectability, self-healing, and tissue adhesion, with mechanical performance, able to facilitate full-thickness skin wound healing, remains challenging. We have developed an injectable micellar hydrogel (AF127/HA-ADH/OHA-Dop) with outstanding adhesive and self-healing properties able to accelerate full-thickness skin wound healing. Dopamine-functionalized oxidized hyaluronic acid (OHA-Dop), adipic acid dihydrazide-modified HA (HA-ADH), and aldehyde-terminated Pluronic F127 (AF127) were employed as polymer backbones. They were cross-linked in situ using Schiff base dynamic covalent bonds (AF127 micelle/HA-ADH network and HA-ADH/OHA-Dop network), hydrogen bonding, and π-π stacking interactions. The resulting multicross-linked double-network design forms a micellar hydrogel. The unique multicross-linked double-network structure endows the hydrogel with both improved injection abilities and mechanical performance while self-healing faster than single-network hydrogels. Inspired by mussel foot adhesive protein, OHA-Dop mimics the catechol groups seen in mussel proteins, endowing hydrogels with robust adhesion properties. We also demonstrate the potential of our hydrogels to accelerate full-thickness cutaneous wound closure and improve skin regeneration with reduced scarring. We anticipate that our hydrogel platform based on a novel multicross-linked double-network design will transform the future development of multifunctional wound dressings.

Summary This paper reports a new method to generate stable and high-brightness electroluminescence (EL) by subsequently growing large/small grains at micro/nano scales with the configuration of attaching small grains on the surfaces of large grains in perovskite (MAPbBr3) films by mixing two precursor solutions (PbBr2 + MABr and Pb(Ac)2·3H2O + MABr). Consequently, the small and large grains serve, respectively, as passivation agents and light-emitting centers, enabling self-passivation on the defects located on the surfaces of light-emitting large grains. Furthermore, the light-emitting states become linearly polarized with maximal polarization of 30.8%, demonstrating a very stable light emission (49,119 cd/m2 with EQE = 11.31%) and a lower turn-on bias (1.9 V) than the bandgap (2.25V) in the perovskite LEDs (ITO/PEDOT:PSS/MAPbBr3/TPBi[50 nm]/LiF[0.7 nm]/Ag). Therefore, mixing large/small grains with the configuration of attaching small grains on the surfaces of large grains by mixing two precursor solutions presents a new strategy to develop high-performance perovskite LEDs., Graphical Abstract, Highlights • Small grains are attached to the surfaces of large grains in perovskite films • Ions can passivate grain boundary defects to enable self-passivation in PeLEDs • Light-emitting states become linearly polarized upon self-passivation • Turn-on voltage is lower than bandgap in perovskite LEDs under self-passivation, Materials Characterization; Optical Materials; Surface

Intrinsic degradation in 100 nm AlQ3 OLED device with strong luminescence was observed while nearly no degradation in 50 nm AlQ3 device with weak luminescence was observed for the same operation time. Based on the EL and PL measurements, it was suggested that penetration of AlQ3 molecules into NPB layer resulted in the increase of electron leakage current, and thus significant loss of current efficiency. A plausible Coulomb effect induced intrinsic degradation mechanism was therefore proposed to explain the experimental results.

Metal halide perovskites have shown rapid development in various fields such as photovoltaics, photodetectors, light-emitting diodes (LEDs), and optically pumped lasers owing to their superior optoelectronic properties. Here, we review the basic optoelectronic properties of halide perovskites from a photophysical perspective. We highlight that halide perovskites are promising in various optoelectronic devices functioning at a wide range of carrier densities. We discuss optically and electrically generated carrier density under two different excitation modes [continuous wave (CW) and pulsed] as well as the impact of carrier density on the optoelectronic behavior of perovskites. Moreover, we discuss lasing actions at high carrier densities and summarize key rules to evaluate the lasing actions. Last, we provide an outlook on perovskite-based electrically pumped lasers. 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) [2009-00971]

One of the most critical challenges in perovskite light-emitting diodes (PeLEDs) lies in poor operational stability. Although field dependent ion migration is believed to play an important role in the operation of perovskite optoelectronic devices, a complete understanding of how it affects the stability of PeLEDs is still missing. Here, we report a unique self-repairing behavior that the electroluminescence of moderately degraded PeLEDs can almost completely restore to their initial performance after resting. We find that the accumulated halides within the hole transport layer undergo back diffusion toward the surface of the perovskite layer during resting, repairing the vacancies and thus resulting in electroluminescence recovery. These findings indicate that one of the dominant degradation pathways in PeLEDs is the generation of halide vacancies at perovskite/hole transport layer interface during operation. We thus further passivate this key interface, which results in a high external quantum efficiency of 22.8% and obviously improved operational stability. Funding Agencies|ERCEuropean Research Council (ERC)European Commission [717026]; Swedish Energy Agency EnergimyndighetenSwedish Energy Agency [48758-1]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; DFGGerman Research Foundation (DFG)European Commission [SPP 2196, 424216076]; China Scholarship CouncilChina Scholarship Council [201906830040]; Nanjing University of Aeronautics and Astronautics PhD short-term visiting scholar project [180608DF06]; Priority Academic Program Development of Jiangsu Higher Education Institutions; Swiss Federal Office of Energy (SFOE)-BFE [SI/501805-01]

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

Understanding the feasibility to couple semiconducting and magnetic properties in metal halide perovskites through interface design opens new opportunities for creating the next generation spin‐related optoelectronics. In this work, a fundamentally new phenomenon of optically induced magnetization achieved by coupling photoexcited orbital magnetic dipoles with magnetic spins at perovskite/ferromagnetic interface is discovered. The depth‐sensitive polarized neutron reflectometry combined with in situ photoexcitation setup, constitutes key evidence of this novel effect. It is demonstrated that a circularly polarized photoexcitation induces a stable magnetization signal within the depth up to 7.5 nm into the surface of high‐quality perovskite (MAPbBr3) film underneath a ferromagnetic cobalt layer at room temperature. In contrast, a linearly polarized light does not induce any detectable magnetization in the MAPbBr3. The observation reveals that photoexcited orbital magnetic dipoles at the surface of perovskite are coupled with the spins of the ferromagnetic atoms at the interface, leading to an optically induced magnetization within the perovskite’s surface. The finding demonstrates that perovskite semiconductor can be bridged with magnetism through optically controllable method at room temperature in this heterojunction design. This provides the new concept of utilizing spin and orbital degrees of freedom in new‐generation spin‐related optoelectronic devices., The depth‐sensitive polarized neutron reflectometry technique reveals the optically induced static magnetization in metal halide perovskite by coupling photoexcited orbital magnetic dipoles with spins at perovskite/ferromagnetic interface. This work demonstrates that perovskite can be bridged with magnetism through optically controllable method in perovskite/ferromagnetic heterojunction, providing the new concept of utilizing spin and orbital degrees of freedom for spin‐related optoelectronics.

Doping has been used as a common method to improve photovoltaic performance in perovskite solar cells (PSCs). This paper reports a new phenomenon that the SnF2 doping can largely increase the exciton-exciton interaction through orbital magnetic dipoles toward increasing dissociation probabilities in lead-free FASnI2Br PSCs. Essentially, when orbit-orbit interaction between excitons occurs, linearly and circularly polarized photoexcitations can inevitably generate different photocurrents, giving rise to a ΔJsc phenomenon. Here, it is found that, when SnF2 doping is used to boost photovoltaic efficiency to 7.61%, the orbit-orbit interaction is increased by a factor of 2.2, shown as the ΔJsc changed from 1.21% to 0.55%. Simultaneously, magnetic field effects of Jsc indicate that increasing orbit-orbit interaction leads to an increase on the spin-orbital coupling in Sn perovskites (FASnI2Br) upon SnF2 doping. This presents a new doping effect occurring in the Sn perovskite solar cell toward enhancing photovoltaic efficiency.

Recent studies have shown that introductions of some organic additives are beneficial for optimizing organic–inorganic hybrid perovskite (OIHP) optoelectronic properties to promote their industrial...

The Raman spectra of two kinds of expansins KT-30 and DA-6 are measured and analyzed in the cases of pure solid-phase and in water solutions. The results show that, KT-30 has much richer and narrower Raman spectral peaks. The first, second, and third strong Raman peaks are respectively located 990.68738 cm−1, 1606.0975 cm−1, and 1327.9379 cm−1. Besides the dense and narrow Raman peaks below 1800 cm−1, there exist three weak peaks within 3050–3410 cm−1. In comparison, fewer spectral peaks can be observed for DA-6. The first and second strong peaks respectively appear at 2883.03760 cm−1 and 2848.4480 cm−1. There exist about 8 peaks below 1500 cm−1. In water solutions, bell-shaped and homogeneous fluorescence background will respectively superpose on the Raman spectra of KT-30 and DA-6 within 100–2500 cm−1 and 400–4000 cm−1. Parts of spectral peaks will be covered accordingly. Moreover, the peak position shifts of KT-30 are very slight. While DA-6 takes the opposite. Its largest shift can even be up to 63.4148 cm−1. The results can supply important fingerprint data for Raman detection of expansins in fruits and vegetables.

The forming/destruction mechanism of conducting filament is essential in understanding the behavior of resistance-memory device. On the basis of filamentary theory, we systematically studied the different electrical performances of both planar and vertical sandwich (metal/organic/metal) memory devices. Bias induced morphological change in gap devices are monitored using scanning electron microscopy system equipped with probes. The in situ images directly demonstrate that with bias increasing, metal clusters emerge inside the channel and further cause sudden switching of device resistance. After clarifying the roles of electrodes and sandwiched organic layer, we conclude a field-dependent filament formation and organics-assistant filament destruction mechanism for resistance memory phenomenon, which should generally exist in all organic electronic devices with metal electrodes.

To deal with the invalidation of commonly employed series model and parallel model in capacitance–voltage (C–V) characterization of organic thin films when current injection is significant, a three-element equivalent circuit model is proposed. On this basis, the expression of real capacitance in consideration of current injection is theoretically derived by small-signal analysis method. The validity of the proposed equivalent circuit and theoretical expression are verified by a simulating circuit consisting of a capacitor, a diode, and a resistor. Moreover, the accurate C–V characteristic of an organic thin film device is obtained via theoretical correction of the experimental measuring result, and the real capacitance is 35.7% higher than the directly measured capacitance at 5-V bias in the parallel mode. This work strongly demonstrates the necessity to consider current injection in C–V measurement and provides a strategy for accurate C–V characterization experimentally.

Organic-inorganic hybrid perovskite thin films with nanostructured polycrystalline grains have shown great potential in various nanoscale optoelectrical applications. Among them, the field of electrical memory has fallen behind due to insufficient knowledge of the related resistive switching characters and mechanisms. In the present work, switching behaviors of perovskite memory devices are systematically analyzed by comparing them with organic memory devices. We found that decreasing the conductivity of a polycrystalline perovskite thin layer would lead to unipolar switching behaviors, which is supplementary to the present perovskite memory family where bipolar switching is commonly reported. Moreover, our proposed symmetrical device with a nanoscale heterolayer structure enables us not only to achieve highly reproducible unipolar switching devices but also to settle the argument whether microconducting channels exist within perovskite memory devices through characterizing the microscopic morphological homogeneity. Surprisingly, the scanning electron microscopy results show that partial 10 pm large perovskite grains would be decomposed into various 100 nm small grains under high external bias, indicating the presence of microconducting channels. Furthermore, energy-dispersive X-ray spectroscopy results together with photoluminescence results of the perovskite thin film before and after applying bias are nearly identical, demonstrating that microconducting channels are formed without any difference in compositions or optical properties. Our discoveries provide a practical strategy to achieve electrical storage via organic-inorganic hybrid perovskite thin-film devices. Funding Agencies|National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [11574049]

In article 2004488, Miaosheng Wang, Valeria Lauter, Bin Hu and co‐workers discovered a fundamentally new phenomenon of optically induced magnetization achieved by coupling photoexcited orbital magnetic dipoles with magnetic spins at perovskite/ferromagnetic interface. In operando polarized neutron reflectometry combined with in situ photoexcitation, constitutes key evidence of this novel effect. Image credit: Oak Ridge National Laboratory/Jill Hemman. [Image: see text]

The vertically ordered (small-to-large n) quasi-2D perovskite films serve as common approaches to facilitate directional charge transfer. Here, we report a different strategy of uniformly arranging different-n-value nanoplates (PEA(2)MA(n-1)Pb(n)I(3n+1)) by introducing vacuum poling treatment to enforce nucleation during crystallization. This uniform distribution is verified by delicate mechanical tape-peeling method while monitoring optical absorption, photoluminescence (PL), and energy-dispersive X-ray spectroscopy (EDS). With uniform distribution, efficient carrier transfer within 10 ps is revealed by transient absorption. Moreover, record-high fill factor (FF) of 82.4% with power conversion efficiency (PCE) of 18.04% (Voc = 1.223 V, Jsc = 17.91 mA/cm(2)) was demonstrated. Superior stability is achieved with retaining 96.1% of initial efficiency after 8-month storage and maintaining 97 7% at 80'C for over 180 h. This uniformly arranging different-n-value nanoplates offers a new material engineering strategy to enhance carrier transfer and extraction for developing high-efficiency and stable quasi-2D perovskite solar cells.

Optoelectronic behavior in materials such as organic/inorganic hybrid perovskites depend on a complex interplay between fast (electronic) and slower (ionic) processes. These processes are thought to be influenced by structural inhomogeneities (e.g. interfaces and grain boundaries) bringing forward the necessity for development of techniques capable of correlating nanostructure and photo-transport behavior. While Kelvin probe force microscopy (KPFM) is ideally suited to map surface potentials on relevant length scales, it lacks sufficient temporal resolution to extract the meaningful system dynamics. Here, we develop a time resolved surface photovoltage (SPV) measurement based on full information capture of the photodetector stream during open loop KPFM operation. G-Mode, or G-KPFM allows quantification of SPV with microsecond temporal and nanoscale spatial resolution. Using this technique, we observe concurrent spatial and fast temporal variations in the SPV generated across a methylammonium lead bromide (MAPbBr3) thin film, a possible indicator relating microstructure with heterogenous photo-transport behavior. We further demonstrate the advantage of adopting big data analytics including unsupervised clustering methods to quickly discern spatial variability in the information rich SPV dataset. Beyond G-KPFM, such clustering methods will be useful for interpretation of the multidimensional datasets arising from the growing number of time resolved KPFM approaches now available.

Two peaks are observed in the capacitance–voltage (C–V) characteristics of electron-transport fullerene (C60 or C70)/Bphen based devices. The experimental results suggest that the mobile carriers generated from unintentional doping and trapped carriers are the origins of these two peaks, just the same as those of hole-transport devices. In addition, the polarity of one C–V peak voltage (the voltage corresponding to the peak capacitance) reverses as the Bphen layer thickness increases. The transient photo-voltage (TPV) signals show a polarity reversal of the internal electric field, confirming the related phenomenon.

Capacitance–voltage ( C – V ) characteristics of organic molecular semiconductors attracted much research interest recently, but no convincing physical mechanism has been established so far. In this work, the C – V characteristics of pentacene-based devices have been systematically investigated at various frequencies. Only one peak occurs when the measuring frequency is less than 3 kHz or greater than 8 kHz. While within the frequency range between the two, two C – V peaks are observed with quite different dependence on temperature, which suggests that the origins of these two C – V peaks are respectively mobile holes and trapped carriers. This conclusion is also experimentally validated with the C – V characteristics of intentionally doped devices.

An ultra-thin molybdenum(VI) oxide (MoO3) modification layer can significantly improve hole injection from an electrode even though the MoO3 layer does not contact the electrode. We find that as the thickness of the organic layer between MoO3 and the electrode increases, the hole injection first increases and it then decreases. The optimum thickness of 5 nm corresponds to the best current improvement 70%, higher than that in the device where MoO3 directly contacts the Al electrode. According to the 4,4-bis[N-(1-naphthyl)-N-phenyl-amino] biphenyl (NPB)/MoO3 interface charge transfer mechanism and the present experimental results, we propose a mechanism that mobile carriers generated at the interface and accumulated inside the device change the distribution of electric field inside the device, resulting in an increase of the probability of hole tunneling through the injection barrier from the electrode, which also explains the phenomenon of hole injection enhanced by MoO3/NPB/Al composite anode. Based on this mechanism, different organic materials other than NPB were applied to form the composite electrode with MoO3. Similar current enhancement effects are also observed.

Polarization effects on optoelectronic behaviors in perovskite-based devices are difficult to address due to quick electronic polarization relaxation and ionic polarization from mobile ions. Here we show the effects of polarized excited states on photoluminescence and photocurrent in MAPbBr3 thin-film devices. We found optically polarized transition dipoles, oriented paralleled and perpendicular to device built-in field, give rise to significantly different photoluminescence and photocurrent outcomes. It provides a new understanding that controlling domain geometry can further enhance the light-emitting and photovoltaic performance of perovskite-based applications. The observation proves that the anisotropy of photoexcited transition dipoles is existed in the electronic states of MAPbBr3. Particularly, this indicates that photo-induced electronic polarization can be shown as photoinduced dielectric polarization at the dipolar polarization regime, which impacts device performance. We also observed that increasing photoexcitation intensity leads to a decreases on both field-induced photoluminescence quenching and field-induced photocurrent enhancing, which implies a cooperative interaction between transition dipoles of increased density that favors light emission but infavors charge dissociation. This provides a critical understanding on why organic-inorganic hybrid perovskites can function as efficient photovoltaic and light-emitting materials at low and high excitation intensities, respectively. Our estimation shows that, by manipulating the ratio of dipole orientation, the efficiencies of perovskite-based LEDs and solar cells could be improved by 50% and 18%, respectively. Clearly, the polarization effect presents a new insight on further controlling photovoltaic and light-emitting actions by manipulating the polarization of excited states in perovskite optoelectronics.

This paper reports an amplified spontaneous emission (ASE) initiated by intrinsically passivating grain boundary defects and aligning transition dipoles in polycrystalline perovskite (MAPbBr3) films. The method is developed by using concurrently occurring fast and slow growths to attach small grains on surfaces of large grains toward low-threshold ASE. This materials processing utilizes one-step solution method of mixing two MAPbBr3 precursor (PbBr2-based and Pb(Ac)2 · 3H2O-based) solutions to control two subsequent growths: quickly growing large grains followed by slowly growing small grains, leading to unique emitting centers from large grains and self-doping agents from small grains. With this design, spectral narrowing phenomenon is observed from the large grains with the full width at half maximum decreasing from 21 to 4 nm when the pumping fluence is increased from 2 to 10 µW, generating an efficient ASE. Concurrently, the observed ASE shows a linear polarization reaching 21.1%, indicating that the transition dipoles in large grains are linearly polarized with coherent interaction. Therefore, this processing strategy presents a unique method to intrinsically passivate grain boundary defects and align transition dipoles toward developing ASE by attaching small grains (serving as passivation agent) to the surfaces of large grains (functioning as light-emitting centers).

Lead halide perovskites have demonstrated outstanding achievements in photoelectric applications owing to their unique properties. However, the moisture sensitivity of lead halide perovskite has ra ...

Organic photovoltaics (OPVs) with three types of double anode buffer layers (DABLs), i.e., 4.5 nm hole-transport material 4,4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl layer, 1 nm electron-transport material Bphen, and 1 nm typical insulator LiF layer, respectively, deposited onto 10 nm MoO3 layer, were fabricated. All these three DABLs can improve the efficiency of CuPc/C60 based planar heterojunction OPV, especially with about 10% enhancement of short-circuit current (ISC). Based on the external quantum efficiency (EQE) and transient photovoltage (TPV) measurements, a mechanism of depressing harmful exciton dissociation at the MoO3/CuPc interface has been proposed. This harmful dissociation results in exciton loss within the CuPc layer, while a proper ultrathin layer inserted at MoO3/CuPc interface can effectively depress the dissociation and thus improve the total photocurrent.

Self-assembled SiGe quantum rings (QRs) on Si(001) are capped with Si layers at temperatures varying from 200 to 550 °C; their shape changes after Si capping are investigated by atomic force microscopy (AFM) and transmission electron microscopy (TEM). The SiGe QR shape can be well preserved in the Si capping layer when the substrate temperature at Si capping is lower than 350 °C, whereas the SiGe QR shape transforms from a ring to a mound when the substrate temperature is higher than 480 °C. The SiGe QR shape could also be well preserved in the Si capping layer with an initial low temperature (300 °C) Si capping followed by a relatively high temperature (550 °C) Si capping. A comparison of the photoluminescence (PL) spectra of the SiGe QRs and the SiGe quantum dots (QDs) is also reported.

The morphologies of self-assembled Ge/Si(001) islands with initial Si capping at a temperature of 640 °C are investigated by atomic force microscopy. Before Si capping, the islands show a metastable dome shape with very good size uniformity. This dome shape changes to a pyramid shape with {103} facets at a Si capping thickness of 0.32 nm, and then changes to pyramid shapes with {104} and {105} facets at Si capping thicknesses of 0.42 and 0.64 nm, respectively. Noteworthy is that islands with one side retained their dome shape while the other three sides that changed to {103} facets are observed at a Si capping thickness of 0.18 nm. These observations indicate that island shape change with Si capping is a kinetic rather than thermodynamic process. The atomic processes associated with this island shape change are kinetically limited at a low temperature of 400 °C, and no significant change in size and shape of islands is observed when Si capping layers are deposited at this temperature.

Despite quick development of perovskite light-emitting diodes (PeLEDs) during the past few years, the fundamental mechanisms on how ion migration affects device efficiency and stability remain unclear. Here, it is demonstrated that the dynamic redistribution of mobile ions in the emissive layer plays a key role in the performance of PeLEDs and can explain a range of abnormal behaviours commonly observed during the device measurement. The dynamic redistribution of mobile ions changes charge-carrier injection and leads to increased recombination current; at the same time, the ion redistribution also changes charge transport and results in decreased shunt resistance current. As a result, the PeLEDs show hysteresis in external quantum efficiencies (EQEs) and radiance, that is, higher EQEs and radiance during the reverse voltage scan than during the forward scan. In addition, the changes on charge injection and transport induced by the ion redistribution also well explain the rise of the EQE/radiance values under constant driving voltages. The argument is further rationalized by adding extra formamidinium iodide (FAI) into optimized PeLEDs based on FAPbI(3), resulting in more significant hysteresis and shorter operational stability of the 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) [2009-00971]; NSFCNational Natural Science Foundation of China (NSFC) [61774077]; Research and Development Program in Key Areas of Guangdong Province [2019B1515120073, 2019B090921002, 2019B010132004]; China Scholarship CouncilChina Scholarship Council

Orientational manipulation of transition dipole moment (TDM) plays an important role in controlling the polarization of excited states in light emission as well as lasing actions. The present work discovers vertically aligned TDMs in hybrid perovskite films through angle-resolved photoluminescence (PL) measurements, which show enhanced emission through the film edge. With increasing excitation intensity, the edge emission induced by these vertically aligned TDMs becomes dominant and eventually leads to amplified spontaneous emission (ASE) through the edge view. Meanwhile, polarized emission of both PL and electroluminescence (EL) provides further evidence for vertically aligned TDMs. Surprisingly, the degree of polarization (DOP) through the film edge is increased when grain boundary defects are passivated through either stochiometric engineering or self-passivation by mobile ions under working conditions. With increasing DOP, ASE threshold of the perovskite film is reduced owing to enhanced collective behaviors of light-emitting states. This work presents a useful method to manipulate TDMs in organic-inorganic hybrid perovskites. Funding Agencies|ERC Starting GrantEuropean Research Council (ERC) [717026]; Swedish Energy Agency EnergimyndighetenSwedish Energy Agency [48758-1]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009-00971]