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1.
    
Metal halide perovskite optoelectronic devices have made significant progress over the past few years, but precise control of charge carrier density through doping is essential for optimizing these devices. In this study, the potential of using an organic salt, N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, as a dopant for Sn-based perovskite devices, is explored. Under optimized conditions, the thin film transistors based on the doped 2D/3D perovskite PEAFASnI3 demonstrate remarkable improvement in hole mobility, reaching 7.45 cm2V−1s−1 with a low subthreshold swing and the smallest sweep hysteresis (ΔVhysteresis = 2.27 V) and exceptional bias stability with the lowest contact resistance (2.2 kΩ cm). The bulky chemical structure of the dopant prevents it from penetrating the perovskite lattice and also surface passivation against Sn oxidation due to its hydrophobic nature surface. This improvement is attributed to the bifunctional effect of the dopant, which simultaneously passivates defects and improves crystal orientation. These findings provide new insights into potential molecular dopants that can be used in metal halide perovskite devices.  相似文献   

2.
    
Metal halide perovskites have attracted a considerable amount of research attention with significant progress made in the field of optoelectronics. Despite their outstanding electrical characteristics, structural defects impede their potential performance due to the polycrystalline nature of solution-processed perovskite films. Herein, the effective p-type doping and defect passivation of phenethylammonium tin iodide ((PEA)2SnI4) perovskite films using xanthate additives as a sulfur source is reported. Sulfur can be introduced to the iodine vacancies mainly at the grain boundaries of the perovskite film, passivating the electrical defects originating from the iodine vacancy and increasing the hole concentration. The Fermi-level shift toward the valence band maximum of the sulfur-doped perovskite film is confirmed using ultraviolet photoemission spectroscopy, resulting in p-type doping. Finally, the electrical performance improvement for the 0.2% sulfur-doped (PEA)2SnI4 thin-film transistor with a mobility of 1.45 cm2 V−1 s−1, an on/off ratio of 2.9 × 105 is demonstrated, and hysteresis of 10 V is reduced.  相似文献   

3.
    
The interaction of free carriers with defects and some critical defect properties are still unclear in methylammonium lead halide perovskites (MHPs). Here, a multi-method approach is used to quantify and characterize defects in single crystal MAPbI3, giving a cross-checked overview of their properties. Time of flight current waveform spectroscopy reveals the interaction of carriers with five shallow and deep defects. Photo-Hall and thermoelectric effect spectroscopy assess the defect density, cross-section, and relative (to the valence band) energy. The detailed reconstruction of free carrier relaxation through Monte Carlo simulation allows for quantifying the lifetime, mobility, and diffusion length of holes and electrons separately. Here, it is demonstrated that the dominant part of defects releases free carriers after trapping; this happens without non-radiative recombination with consequent positive effects on the photoconversion and charge transport properties. On the other hand, shallow traps decrease drift mobility sensibly. The results are the key for the optimization of the charge transport properties and defects in MHP and contribute to the research aiming to improve perovskite stability. This study paves the way for doping and defect control, enhancing the scalability of perovskite devices with large diffusion lengths and lifetimes.  相似文献   

4.
    
The presence of defects in thermoelectric materials plays a significant role in the modification their properties by influencing the behavior of electrons and phonons. Dopants with a unique f‐orbital can directly cause distortions in electronic density of states (eDOS) and phonon transport mechanism by intentionally inducing defects in their lattice. The theoretical and experimental outcomes of engineered vacancy defects are investigated by intentional doping of f‐block rare earth elements in β‐Zn4Sb3. Thermoelectric behavior breaks down the inverse relation and results in a parallel increase in Seebeck coefficient and electrical conductivity for β‐(Zn0.997Ce0.003)4Sb3 and β‐(Zn0.997Er0.003)4Sb3. This synergistic response triples the power factor of a thermoelectric β‐Zn4Sb3 system realized by the impurity induced resonant distortion in eDOS. From first principle GGA + U calculations, the above‐mentioned unconventional properties are attributed to the effect of doping induced vacancy formation and the formation of resonant impurity levels. Hence, it is postulated that defect engineering can be a broad strategy to improve the power factor of the system and can be extended to other thermoelectric materials.  相似文献   

5.
    
The rational design of heterojunctions based on metal halide perovskites (MHPs) is an effective route to create novel photocatalysts to run relevant solar-driven reactions. In this work, an experimental and computational study on the synergic coupling between a lead-free Cs3Bi2Br9 perovskite derivative and g-C3N4 is presented. A relevant boost of the hydrogen photogeneration by more than one order of magnitude is recorded when going from pure g-C3N4 to the Cs3Bi2Br9/g-C3N4 system. Effective catalytic activity is also achieved in the degradation of the organic pollutant with methylene blue as a model molecule. Based upon complementary experimental outputs and advanced computational modeling, a rationale is provided to understand the heterojunction functionality as well as the trend of hydrogen production as a function of perovskite loading. This work adds further solid evidence for the possible application of MHPs in photocatalysis, which is emerging as an extremely appealing and promising field of application of these superior semiconductors.  相似文献   

6.
    
Mixed‐cation lead mixed‐halide perovskites are employed as the photoactive material in single‐layer solution‐processed photodetectors fabricated with coplanar asymmetric nanogap Al–Au and indium tin oxide–Al electrodes. The nanogap electrodes, bearing an interelectrode distance of ≈10 nm, are patterned via adhesion lithography, a simple, low‐cost, and high‐throughput technique. Different electrode shapes and sizes are demonstrated on glass and flexible plastic substrates, effectively engineering the device architecture, and, along with perovskite film and material optimization, paving the way toward devices with tunable operational characteristics. The optimized coplanar nanogap junction perovskite photodetectors show responsivities up to 33 A W?1, specific detectivity on the order of 1011 Jones, and response times below 260 ns, while retaining a low dark current (0.3 nA) under ?2 V reverse bias. These values outperform the vast majority of perovskite photodetectors reported so far, while avoiding the complicated fabrication steps involved in conventional multilayer device structures. This work highlights the promising potential of the proposed asymmetric nanogap electrode architecture for application in the field of flexible optoelectronics.  相似文献   

7.
    
Tin‐based perovskites have long remained a side topic in current perovskite optoelectronic research. With the recent efficiency improvement in thin film solar cells and the observation of a long hot carrier cooling time in formamidinium tin iodide (FASnI3), a thorough understanding of the material's photophysics becomes a pressing matter. Since pronounced background doping can easily obscure the actual material properties, it is of paramount importance to understand how different processing conditions affect the observed behavior. Using photoluminescence spectroscopy, thin films of FASnI3 fabricated through different protocols are therefore investigated. It is shown that hot carrier relaxation occurs much faster in highly p‐doped films due to carrier–carrier scattering. From high quality thin films, the longitudinal optical phonon energy and the electron–phonon coupling constant are extracted, which are fundamental to understanding carrier cooling. Importantly, high quality films allow for the observation of a previously unreported state of microsecond lifetime at lower energy in FASnI3, that has important consequences for the discussion of long lived emission in the field of metal halide perovskites.  相似文献   

8.
    
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9.
    
As the requirements and expectation for displays in society are growing, higher standards of the display technology are proposed, including wider color gamut, higher color purity, and higher resolution. The recent emergence of light‐emitting halide perovskites has come with numerous advantages, such as high charge‐carrier mobility, tunable emission wavelength, narrow emission linewidth, and intrinsically high photoluminescence quantum yield. Recent advancement of perovskite‐based light‐emitting diodes (PeLEDs) as a promising technology for next‐generation displays is reviewed. Here, how the attractive optical and electrical properties of perovskite materials can be translated into high PeLED performance are discussed, and working mechanisms and optimization approaches of both perovskite materials and the respective devices are analyzed. On the material side this includes the control of size and composition of perovskites grains and nanocrystals, surface and interface passivation, doping and alloying, while on the device side this includes the interfacial engineering and energy level adjustments, and photon emission enhancement. Several challenges such as performance of blue PeLEDs, the environmental and operational stability of PeLEDs, and the toxicity issues of lead halide perovskites are discussed, and perspectives on future developments of perovskite materials and PeLEDs for the display technology are offered.  相似文献   

10.
    
The demand for high-energy radiation detection systems combining high sensitivity, low-cost and large-area fabrication has pushed the research on hybrid perovskites as promising materials for X- and γ-photon detection, thanks to their high Z atoms, solution-processability, and high optoelectronic performance. Here, flexible direct X-ray detectors are demonstrated with outstanding real-time detection properties. They are based on printed micrometers-thick films of methylammonium lead triiodide nanocrystals inks, formulated in low boiling point and benign solvents. Record optoelectronic performances, such as high X-ray sensitivity (up to 2270 µC Gy−1 cm−2), radiation tolerance over 2.2 Gy of total dose, and fast response time (48 ms) have been achieved by using a simple device architecture and materials processing The functionality under strong bending stress (strain > 10%) and under high X-ray energy (up to 150 keV) has been assessed, opening the way for flexible real-time direct radiation detectors and imagers, operating at low-voltages (bias < 4V) and apt to be fabricated by means of large-area scalable processes.  相似文献   

11.
    
Organic-based energy harvesting devices can contribute to a sustainable solution for the transition to renewable energy sources. The concept of ionic thermoelectrics (iTE) has been recently proposed and motivated by the high values of thermo-voltage in electrolytes. So far, most research has focused on developing new electrolytes with high Seebeck coefficient. Despite the major role of the electrode materials in supercapacitors and batteries, the effect of various electrodes on energy harvesting in iTE devices has not been widely studied. In this work, the conducting polymer poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) is investigated as the functional electrodes in iTE supercapacitors. Through investigating the thermo-voltage of iTEs of the same electrolyte with varying composition of PEDOT electrodes, it is identified that the different PSS content greatly affects the overall thermo-induced voltage coefficient, Seff (i.e., effective thermopower). The permselective polyanion in the electrode causes cation concentration differences at the electrode/electrolyte interface and contributes to an interfacial potential drop that is temperature dependent. As a result, the overall thermo-voltage of the device possesses both an interfacial and a bulk contribution. The findings extend the fundamental understanding of iTE effect with functional electrodes, which could lead a new direction to enhance the heat-to-electricity conversion.  相似文献   

12.
    
Seebeck coefficient is a widely studied semiconductor property. Conventional Seebeck coefficient measurements are based on DC voltage measurement. Normally this is performed on samples with moderate resistances (e.g., below a few MΩ level). Certain semiconductors are intrinsic and highly resistive. Many examples can be found in optical and photovoltaic materials. The hybrid halide perovskites that have gained extensive attention recently are a good example. Despite great attention from the materials and physics communities, few successful studies exist of the Seebeck coefficient of these compounds, for example CH3NH3PbI3. An AC‐technique‐based Seebeck coefficient measurement is reported, which makes high‐quality Seebeck voltage measurements on samples with resistances up to the 100 GΩ level. This is achieved through a specifically designed setup to enhance sample isolation and increase capacitive impedance. As a demonstration, Seebeck coefficient measurement of a CH3NH3PbI3 thin film is performed at dark, with sample resistance 150 GΩ, and found S = +550 µV K−1. The strategy reported could be applied to the studies of fundamental transport parameters of all intrinsic semiconductors that have not been feasible.  相似文献   

13.
    
SnSe has attracted much attention due to the excellent thermoelectric (TE) properties of both p‐ and n‐type single crystals. However, the TE performance of polycrystalline SnSe is still low, especially in n‐type materials, because SnSe is an intrinsic p‐type semiconductor. In this work, a three‐step doping process is employed on polycrystalline SnSe to make it n‐type and enhance its TE properties. It is found that the Sn0.97Re0.03Se0.93Cl0.02 sample achieves a peak ZT value of ≈1.5 at 798 K, which is the highest ZT reported, to date, in n‐type polycrystalline SnSe. This is attributed to the synergistic effects of a series of point defects: V Se .. , Cl Se . , V Sn , , , Re Sn × , Re 0 . In those defects, the V Se .. compensates for the intrinsic Sn vacancies in SnSe, the Cl Se . acts as a donor, the V Sn , , acts as an acceptor, all of which contribute to optimizing the carrier concentration. Rhenium (Re) doping surprisingly plays dual‐roles, in that it both significantly enhances the electrical transport properties and largely reduces the thermal conductivity by introducing the point defects, Re Sn × , Re 0 . The method paves the way for obtaining high‐performance TE properties in SnSe crystals using multipoint‐defect synergy via a step‐by‐step multielement doping methodology.  相似文献   

14.
    
Organic-inorganic hybrid halide perovskites show a unique two-channel thermal transport through propagons and diffusons, largely affecting other energy carriers for opto- and thermoelectric applications. Taking CH3NH3PbI3 as a prototype, the impact of iodine vacancy point defects on the two-channel thermal transport is investigated using theoretical calculations and experimental validations. This work finds that iodine vacancies suppress the thermal transport in the propagon channel significantly, but less in the diffuson channel. This results in a weaker reduction of the total thermal conductivity (TC) than that predicted by the classical Klemens model. The TC reduction in the diffuson channel is mainly attributed to the declined vibrational density of states. Moreover, low-frequency diffusons transformed from propagons compensate the reduction of TC in the diffuson channel, resulting in a dominant contribution from the diffuson channel to the total TC, which is 55% to 85% for 0% to 6% vacancy concentration. CH3NH3PbI3 also shows ultra-defect-tolerant diffusonic thermal transport, ≈1–2 orders of magnitude lower than diamond in the defect sensitivity factor. This work shows both scientific insights into the new two-channel thermal transport mechanism in complex material systems with disorder, and technological significance on halide perovskites for solar cell, light-emitting diode, thermoelectric, and memristor applications.  相似文献   

15.
    
Lead halide perovskites are a remarkable class of materials that have emerged over the past decade as being suitable for application in a broad range of devices, such as solar cells, light‐emitting diodes, lasers, transistors, and memory devices. While they are often solution‐processed semiconductors deposited at low temperatures, perovskites exhibit properties one would only expect from highly pure inorganic crystals that are grown at high temperatures. This unique phenomenon has resulted in fast‐paced progress toward record device performance. Unfortunately, the basic science behind the remarkable nature of these materials is still not well understood. This review assesses the current understanding of the photoluminescence properties of metal halide perovskite materials and highlights key areas that require further research. Furthermore, the need to standardize the methods for characterization of PL in order to improve comparability, reliability, and reproducibility of results is emphasized.  相似文献   

16.
    
To efficiently harvest the abundant waste heat on earth is of great significance for sustainable development. Thermoelectric materials can be used to directly convert heat into electricity, and ionic thermoelectric materials like ionic liquids (ILs) are considered as the next-generation thermoelectric materials. It is important to develop novel methods to improve the overall thermoelectric properties particularly the thermopower. Herein, the great enhancement in the thermopower of 1-ethyl-3-methylimidazolium dicyanamide (EMIM:DCA) is reported that is an IL by introducing zeolitic imidazolate framework (ZIF-8) that is a metal-organic framework (MOF) for the first time. The presence of 40 wt.% ZIF-8 can greatly increase the ionic thermopower of EMIM:DCA from 8.8 to 31.9 mV K−1 at room temperature, and the ZIF-8/EMIM:DCA mixture at the ZIF-8 loading of 10 wt.% can exhibit a ZTi value of 3.1, notably higher than that (0.59) of neat EMIM:DCA. The enhancement in the thermopower is attributed to the increase in the difference of the mobilities of EMIM+ and DCA− by ZIF-8. Because DCA− is smaller while EMIM+ is larger than the pore size of ZIF-8, the DCA− transport is hindered by ZIF-8, while EMIM+ can bypass ZIF-8.  相似文献   

17.
    
The role of tin fluoride in defining the complex surface chemistry of tin halide perovskites (THP) is investigated. It is shown that oxygen is found on the surface of tin perovskite thin films even if prepared under a virtually inert environment; however, the presence of SnF2 strongly affects the chemical nature of the found species. Oxygen primarily binds to tin in the form of SnO2 only when SnF2 is added to the precursor solution, while it preferentially binds to carbon and hydrogen in pristine materials. Thanks to the spatial mapping of both the local chemical environment and photoluminescence, it is shown that pristine films have a higher accumulation of iodine at the grain boundaries while the addition of SnF2 allows for preserving the perovskite phase and reducing chemical and optical heterogeneities. Finally, SnF2 does not help in avoiding nor slowing down the degradation of the perovskite film when exposed to ambient air and oxidation occurs on the whole THP-grain surface. These results provide insightful guidance toward understanding oxidation in THPs and elucidate its detrimental effect on the material's properties.  相似文献   

18.
    
Core/shell structured metal halide perovskite nanocrystals (NCs) are emerging as a type of material with remarkable optical and electronic properties. Research into this field has been developing and expanding rapidly in recent years, with significant advances in the studies of the shell growth mechanism and in understanding of properties of these materials. Significant enhancement of both the stability and the optical performance of core/shell perovskite NCs are of particular importance for their applications in optoelectronic technologies. In this review, the recent advances in core/shell structured perovskite NCs are summarized. The band structures and configurations of core/shell perovskite NCs are elaborated, the shell classification and shell engineering approaches, such as perovskites and their derivative shells, semiconductor shell, oxide shell, polymer shell, etc. are reviewed, and the shell growth mechanisms are discussed. The prospective of these NCs in lighting and displays, solar cells, photodetectors, and other devices is discussed in the light of current knowledge, remaining challenges, and future opportunities.  相似文献   

19.
    
Metal halide perovskites (MHPs) as one of the most active materials gained tremendous attention in the past decade because of their outstanding performance in optoelectronics. Owing to their perovskite structure, ferroelectricity is anticipated in this class of materials. However, whether MHPs are ferroelectric or not remains elusive. Recently, discussion regarding ferroelasticity in MHPs has been also raised. In addition, ionic motion and structural dynamics are well known in MHPs. The interplay of these phenomena including electric polarization, strain, ionic motion, and structural dynamics can have a significant impact on optoelectronics. Therefore, understanding the mechanism behind these phenomena and their interactions is critical in addressing the controversy about ferroicity of MHPs and developing functional devices. Here, the current findings about MHP's ferroicity are summarized and evaluated and a perspective for the future is provided. It is suggested that ionic motion and associated phenomena, coupled with ferroic behavior, are the main drivers behind MHPs functionality. The challenges are also discussed in probing MHPs’ ferroicity and what new measurement modalities are needed to fully understand and characterize MHP behavior. Finally, it is discussed how ferroic and strain can affect the optoelectronic performance of MHPs and how they can be used for engineering of higher performance devices.  相似文献   

20.
    
Metal halide perovskites (MHPs) have become a promising candidate in a myriad of applications, such as light-emitting diodes, solar cells, lasing, photodetectors, photocatalysis, transistors, etc. This is related to the synergy of their excellent features, including high photoluminescence quantum yields, narrow and tunable emission, long charge carrier lifetimes, broad absorption spectrum along with high extinction absorptions coefficients, among others. However, the main bottleneck is the poor stability of the MHPs under ambient conditions. This is imposing severe restrictions with respect to their industrialized applications and commercialization. In this context, metal oxide (MOx) coatings have recently emerged as an efficient strategy toward overcoming the stabilities issues as well as retaining the excellent properties of the MHPs, and therefore facilitate the development of the related devices’ stabilities and performances. This review provides a summary of the recent progress on synthetic methods, enhanced features, the techniques to assess the MHPs@MOx composites, and applications of the MHPs@MOx. Specially, novel approaches to fabricate the composites and new applications of the composites are also reported in this review for the first time. This is rounded by a critical outlook about the current MHPs’ stability issues and the further direction to ensure a bright future of MHPs@MOx.  相似文献   

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