Sequential Spin Research Articles

Over 18.2% efficiency of layer–by–layer all–polymer solar cells enabled by homoleptic iridium(III) carbene complex as solid additive

The vertical phase distribution of active layers plays a vital role in balancing exciton dissociation and charge transport for achieving efficient polymer solar cells (PSCs). The layer–by–layer (LbL) PSCs are commonly prepared by using sequential spin–coating method from donor and acceptor solutions with distinct solvents and solvent additives. The enhanced exciton dissociation is expected in the LbL PSCs with efficient charge transport in the relatively neat donor or acceptor layers. In this work, a series of LbL all–polymer solar cells (APSCs) were fabricated with PM6 as donor and PY–DT as acceptor, and triplet material m–Ir(CPmPB)3 is deliberately incorporated into PY–DT layer to prolong exciton lifetimes of active layers. The power conversion efficiency (PCE) of LbL APSCs is improved to 18.24% from 17.32% by incorporating 0.3 wt% m–Ir(CPmPB)3 in PY–DT layer, benefiting from the simultaneously enhanced short–circuit current density (JSC) of 25.17 mA cm−2 and fill factor (FF) of 74.70%. The enhancement of PCE is attributed to the efficient energy transfer of m–Ir(CPmPB)3 to PM6 and PY–DT, resulting in the prolonged exciton lifetime in the active layer and the increased exciton diffusion distance. The efficient energy transfer from m–Ir(CPmPB)3 to PM6 and PY–DT layer can be confirmed by the increased photoluminescence (PL) intensity and the prolonged PL lifetime of PM6 and PY–DT in PM6 + m–Ir(CPmPB)3 and PY–DT + m–Ir(CPmPB)3 films. This study indicates that the triplet material as solid additive has great potential in fabricating efficient LbL APSCs by prolonging exciton lifetimes in active layers.

Direct observation of photoinduced sequential spin transition in a halogen-bonded hybrid system by complementary ultrafast optical and electron probes

A detailed understanding of the ultrafast dynamics of halogen-bonded materials is desired for designing supramolecular materials and tuning various electronic properties by external stimuli. Here, a prototypical halogen-bonded multifunctional material containing spin crossover (SCO) cations and paramagnetic radical anions is studied as a model system of photo-switchable SCO hybrid systems using ultrafast electron diffraction and two complementary optical spectroscopic techniques. Our results reveal a sequential dynamics from SCO to radical dimer softening, uncovering a key transient intermediate state. In combination with quantum chemistry calculations, we demonstrate the presence of halogen bonds in the low- and high-temperature phases and propose their role during the photoinduced sequential dynamics, underscoring the significance of exploring ultrafast dynamics. Our research highlights the promising utility of halogen bonds in finely tuning functional properties across diverse photoactive multifunctional materials.

Reducing rejection exponentially improves Markov chain Monte Carlo sampling

The choice of transition kernel critically influences the performance of the Markov chain Monte Carlo method. Despite the importance of kernel choice, guiding principles for optimal kernels have not been established. Here, we propose a one-parameter rejection control transition kernel that can be applied to various Monte Carlo samplings and demonstrate that the rejection process plays a major role in determining the sampling efficiency. Varying the rejection probability, we examine the autocorrelation time of the order parameter in the two- and three-dimensional ferromagnetic Potts models. Our results reveal that reducing the rejection rate leads to an exponential decrease in autocorrelation time in sequential spin updates and an algebraic reduction in random spin updates. The autocorrelation times of conventional algorithms almost fall on a single curve as a function of the rejection rate. The present transition kernel with an optimal parameter provides one of the most efficient samplers for general cases of discrete variables.

Application of Hydrosol to Aerosol Based Metrology to Predict Wafer Defects from Process Chemical Contamination

A method for continuous measurement of particle and particle precursor material in high purity liquids using aerosolization and condensation particle courting (A+CPC) is presented. A process for correlating wafter defects with the concentration values measured using A+CPC using Sequential Spin Coating + Surface Enhanced Particle Sizing (SSC + SEPS) is described. The method was applied to monitor the rinsate of an ion exchange resin following the SEMI C93 guide. The results showed correlation between the methods and the concentration values were used to calculate a deposition factor (liquid concentration/surface concentration) on the order of 1E5 (#/ml)/(#/cm2).

Controllable blading interdiffusion of formamidinium iodide on thermal evaporated scalable and conformal lead iodide for efficient perovskite solar cells

Organic-inorganic perovskite solar cells with a rapid improving performance have attracted a broad interest, which are mainly fabricated by either one step antisolvent or sequential two-step spin coating process. The sequential two-step coating process has a fine controllability by separating the deposition of PbI2 and organic salt like formamidinium iodide. However, the spin coating has issues such as the use of toxic solvents, a high solution waste ratio and is not suitable for large-area and textured surface. The developed sequential two-step process combining the thermal evaporation of scalable and conformal PbI2 and a blading process of organic salt is expected for the formation of high-quality perovskite with a high uniformity and conformability. However, the device performance is inferior to the two-step solution coating process. Here we systematically investigated the structure and morphology difference of the PbI2 that deposited by solution coating process and thermal evaporation process, and its effect on perovskite layer quality and device performance. The spin coated solvent coordinated PbI2 formed a porous structure, which is beneficial for organic salt penetration. In contrast, evaporated PbI2 is compact with a smooth surface, and may lead to unwanted 2D structures or un-completed conversion when reacted with organic ammonium salt. A temperature-assisted crystal growth is developed to modulate the crystal growth and a superior perovskite film morphology was obtained from thermal evaporated PbI2. Consequently, a champion efficiency of 19.8 % was realized, which is among the highest values for perovskite solar cells prepared by sequential two-step process with thermal evaporation of PbI2 and blading of organic salts.

Over 17.4% Efficiency of Layer‐by‐Layer All‐Polymer Solar Cells by Improving Exciton Utilization in Acceptor Layer

AbstractLayer‐by‐layer all‐polymer solar cells (LbL all‐PSCs) are prepared with PM6 and PY‐IT by using sequential spin coating method. The exciton dissociation efficiency in acceptor layer near electrode is rather low due to the limited exciton diffuse distance and impossible energy transfer from narrow bandgap acceptor to wide bandgap donor. In this study, less PM6 is incorporated into PY‐IT layer to enhance exciton dissociation in PY‐IT layer near electrode. A power conversion efficiency (PCE) of 17.45% is achieved in the LbL all‐PSCs incorporating 10 wt% PM6 into PY‐IT layer, which is much larger than 16.04% PCE of PM6/PY‐IT‐based LbL all‐PSCs. Over 8% PCE enhancement can be realized by incorporating 10 wt% PM6 into PY‐IT layer, which is attributed to the enhanced exciton utilization efficiency in PY‐IT layers near electrode. The enhanced exciton utilization efficiency in PY‐IT layer can be confirmed from the quenched photoluminescence (PL) emission in PY‐IT:PM6 films. Meanwhile, charge transport in acceptor layers can be optimized by incorporating less PM6, as confirmed from the optimized molecular arrangement. This study indicates that the strategy of incorporating less donor into acceptor layer has great potential in fabricating efficient LbL all‐PSCs by improving exciton utilization efficiency in acceptor layer near electrode.

Zwitterionic Ionic Liquid as Additive for High‐Performance FAPbI3 Perovskite Solar Cells with Negligible Hysteresis

Imidazolium‐based ionic liquids have been established as promising candidates for additives in perovskite solar cells. Herein, 1‐(1‐ethyl‐3‐imidazolium)propane‐3‐sulfonate (EIMS) zwitterionic ionic liquid is studied as additive to enhance the performance of the FAPbI3 perovskite solar cells. The addition of EIMS leads to the generation of porous PbI2 film, which promotes the reaction of PbI2 with FAI solution and thus improves the quality of FAPbI3 perovskite film during the two‐step sequential spin coating. It is revealed that EIMS accelerates the extraction of electron, inhibits the formation of pinhole, and reduces the defect density, which leads to an increased efficiency of 22.1%. The hysteresis index is also reduced from 0.142 to 0.009, which indicates the addition of EIMS can realize a negligible hysteresis behavior in the solar cells. Moreover, devices prepared with EIMS retain above 96% of the original power conversion efficiency (PCE) value after being stored in dry air for 45 days. All these results demonstrate that the imidazolium‐based zwitterionic ionic liquid additive strategy is a promising way for high‐performance perovskite solar cells.

Investigating the Sequential Deposition Route for Mixed Cation Mixed Halide Wide Bandgap Perovskite Absorber Layer

Wide bandgap (Eg) perovskite solar cells (PSCs) are emerging as the preferred choice for top cells in a tandem architecture with crystalline silicon solar cells. Among the wide bandgap perovskites, a mixed cation mixed halide composition containing CsyFA1-yPbI3−xBrx is a popular choice because the presence of bromine widens the bandgap and addition of cesium stabilizes the crystal structure. These perovskite layers are commonly fabricated using one-step spin coating technique; however, sequential spin coating followed by dip coating has been successful in offering better control over the crystallization process for low bandgap absorber layers. In this paper, the fabrication of a Cs0.2FA0.8PbI3−xBrx perovskite absorber layer using the sequential deposition route is reported. The concentration of bromine was varied in the range 0 ≤ x ≤ 1 and optical, structural, and morphological properties of the films were studied. As the concentration was increased, the perovskite showed better crystallinity and the presence of large grains with high surface roughness, indicating the formation of the CsPbBr3 phase. Optically, the perovskite films exhibited higher absorbance in the ultraviolet (UV) range between 300 and 500 nm, hence up to x = 0.3 they can be profitably employed as a wide bandgap photon absorber layer in solar cell applications.

Simulation and Model Checking for Close to Realtime Overtaking Planning

Fast and reliable trajectory planning is a key requirement of autonomous vehicles. In this paper we introduce a novel technique for planning the route of an autonomous vehicle on a straight rural road using the Spin model checker. We show how we can combine Spins ability to identify paths violating temporal properties with sensor information from a 3D Unity simulation of an autonomous vehicle, to plan and perform consecutive overtaking manoeuvres on a traffic heavy road. This involves discretising the sensory information and combining multiple sequential Spin models with a Linear Time Temporal Logic specification to generate an error path. This path provides the autonomous vehicle with an action plan. The entire process takes place in close to realtime using no precomputed data and the action plan is specifically tailored for individual scenarios. Our experiments demonstrate that the simulated autonomous vehicle implementing our approach can drive on average at least 40km and overtake 214 vehicles before experiencing a collision, which is usually caused by inaccuracies in the sensory system. While the proposed system has some drawbacks, we believe that our novel approach demonstrates a potentially powerful future tool for efficient trajectory planning for autonomous vehicles.

Intermediate Evaporation Controlled SnO2/Mo Doped BiVO4 photoanode for Enhanced Photoelectrochemical Performance

The design of multilayer oxide films heterojuctions for photoanodes enables the control of charge transport/transfer and optical properties, and thus leads to efficient photoelectrochemical performance. In this research, a SnO2/Mo-doped BiVO4/ based photoanode was fabricated by sequential spin coating method on an FTO substrate followed by thermal treatment. First, bottom SnO2 layers were deposited, and subsequently Mo doped BiVO4 layers were loaded. When Mo doped BiVO4 layers were coated, intermediate evaporation was controlled by varying temperature condition for a formation of uniform crystalline film, allowing an improved charge separation. The synthesized photoanodes were examined by SEM, TEM, XRD, UV-vis as well as electrochemical measurements.

Binary Self-Assembly of Nanocolloidal Arrays using Concurrent and Sequential Spin Coating Techniques.

This paper reports the binary colloid assembly of nanospheres using spin coating techniques. Polystyrene spheres with sizes of 900 and 100 nm were assembled on top of silicon substrates utilizing a spin coater. Two different spin coating processes, namely concurrent and sequential coatings, were employed. For the concurrent spin coating, 900 and 100 nm colloidal nanospheres of latex were first mixed and then simultaneously spin coated onto the silicon substrate. On the other hand, the sequential coating process first created a monolayer of a 900 nm nanosphere array on the silicon substrate, followed by the spin coating of another layer of a 100 nm colloidal array on top of the 900 nm array. The influence of the processing parameters, including the type of surfactant, spin speed, and spin time, on the self-assembly of the binary colloidal array were explored. The empirical outcomes show that by employing the optimal processing conditions, binary colloidal arrays can be achieved by both the concurrent and sequential spin coating processes.

A comparative study of two-step and three-step methods for coating organometallic lead halide perovskite thin films

Two-step sequential spin coating deposition technique provides a cost-effective and high performance route for the synthesis of the organometallic lead halide perovskite materials. In this method, initially the metal halide film is coated, over which the MAI with a particular concentration is again spin-coated. However, it is difficult to obtain complete conversion of PbI2 in CH3NH3PbI3 perovskite. In this work, we show that good quality perovskite films can be coated by a three-step method to obtain improved conversion to perovskite and with improved materials properties. We have coated the perovskite films by two-step as well as three-step methods and presented a comparison of obtained film properties. Our results show that at lower concentration of MAI, complete conversion of PbI2 does not take place. With increase in MAI concentration, in addition to the perovskite phase an intercalated MAI into PbI2 phase is formed. In three-step coating, good phase of perovskite and improved morphology is obtained at comparatively lower MAI concentration. At higher concentrations of MAI in three-step method, leads to removal of already existing perovskite material and therefore leads to lower absorption.

Study on hysteresis in perovskite solar cells fabricated using different solvents under ambient conditions

We have investigated the dependency of hysteresis in all-ambient-processed perovskite solar cells on the solvent used for the synthesization of perovskite. Methylammonium lead iodide (MAI) perovskite solar cells have been fabricated using the two-step sequential spin coating method. The influences of PbI2 precursor on the cell performance and its hysteresis are investigated using four different solvents of pure dimethylformamide (DMF), pure dimethyl sulfoxide (DMSO) and mixtures of DMF:DMSO with the ratios of (4:1) and (1:4). The results indicate that a small amount of DMSO in DMF leads to produce large grains of perovskite with proper coverages at the interfaces with hole and electron transport layers. The best conversion efficiency of 10.9% was obtained for the cell prepared by the solvent of (4:1) for DMF:DMSO. The best hysteresis was also obtained from the same cell with the hysteresis index of 0.009.

Inconsistency of a Realistic Interpretation of Quantum Measurements: a Simple Example

We use a simple example to illustrate why it is not possible to consider that a measurement reveals an underlying objective reality of a property of a quantum system, that continues the same after the measurement is performed. This kind of incompatibility between realism and quantum mechanics is theoretically demonstrated with an example where sequential spin measurements are performed on a spin-2 quantum particle. We discuss the relation of this result with other works that investigate the concept of reality in quantum mechanics.

Sequential Spin State Transition and Intermetallic Charge Transfer in PbCoO3.

Spin state transitions and intermetallic charge transfers can essentially change material structural and physical properties while excluding external chemical doping. However, these two effects have rarely been found to occur sequentially in a specific material. In this article, we show the realization of these two phenomena in a perovskite oxide PbCoO3 with a simple ABO3 composition under high pressure. PbCoO3 possesses a peculiar A- and B-site ordered charge distribution Pb2+Pb4+3Co2+2Co3+2O12 with insulating behavior at ambient conditions. The high spin Co2+ gradually changes to low spin with increasing pressure up to about 15 GPa, leading to an anomalous increase of resistance magnitude. Between 15 and 30 GPa, the intermetallic charge transfer occurs between Pb4+ and Co2+ cations. The accumulated charge-transfer effect triggers a metal-insulator transition as well as a first-order structural phase transition toward a Tetra.-I phase at the onset of ∼20 GPa near room temperature. On further compression over 30 GPa, the charge transfer completes, giving rise to another first-order structural transformation toward a Tetra.-II phase and the reentrant electrical insulating behavior.

A Review on Halide Perovskite Film Formation by Sequential Solution Processing for Solar Cell Applications

Perovskite solar cell performance is closely related to the quality of the perovskite absorbing layer which is highly dependent on deposition processes. Sequential process is shown to be effective in fabricating both single‐junction and tandem solar cells delivering comparable efficiencies compared with devices by a single‐step process. Sequence processes exhibit the benefits of controlling crystallization speed, overcoming solvent incompatibility, and greater flexibility. Here, mechanisms of film formation in two common sequential solution processes, namely chemical bath deposition and sequential spin coating, showing that film formation is highly dependent on precursors or deposition conditions, are reviewed. Herein, further review is conducted on how three main strategies improve perovskite crystallization. The first is by PbI2 complex formation or via intramolecular exchange which is shown to result in a better perovskite conversion and a more ordered perovskite growth. The second strategy is by changing the condition of perovskite precursors, e.g., by solvent, cation, halide, and additive engineering. The last strategy is by altering precursor dispensing conditions and adding vapor or solvent annealing, thereby affecting reaction conditions. Many of these strategies are demonstrated to improve perovskite film morphology with reduced defects.

High-pressure synthesis of A-site ordered perovskite CaMn3(Fe3Mn)O12 and sequential long-range antiferromagnetic ordering and spin glass transition

An AA’3B4O12-type perovskite oxide CaMn3(Fe3Mn)O12 was synthesized at 8 GPa and 1473 K. X-ray diffraction shows a cubic crystal structure with space group Im-3. The charge states are verified by soft x-ray absorption spectroscopy to be CaMn3+3(Fe3+3Mn4+)O12, where the Ca2+ and Mn3+ are 1:3 ordered respectively at A and A′ sites, while the Mn4+ and Fe3+ are disorderly distributed at B site. The spin interaction of A′-site Mn3+ ions causes a long-range antiferromagnetic phase transition at about 39 K. Subsequently, a spin glass transition is found to occur around 14 K due to the randomly distributed Fe3+ and Mn4+ at B site. Moreover, the spin glass behavior follows a dynamic scaling power law. The temperature dependent resistivity can be well fitted by a 3D Mott variable-range hopping model, indicating the insulating nature of CaMn3(Fe3Mn)O12 due to the strong electron correlation effects.

Singlet-triplet minus mixing and relaxation lifetimes in a double donor dot

We measure singlet-triplet mixing in a precision fabricated double donor dot comprising 2 and 1 phosphorus atoms separated by 16 ± 1 nm. We identify singlet and triplet-minus states by performing a sequential independent spin readout of the two electron system and probe its dependence on magnetic field strength. The relaxation of singlet and triplet states is measured to be 12.4 ± 1.0 s and 22.1 ± 1.0 s, respectively, at Bz = 2.5 T.

Quantitative Correlation of Perovskite Film Morphology to Light Emitting Diodes Efficiency Parameters

This paper reports quantitative correlation of CH3NH3PbBr3 (MAPbBr3) thin film morphology to light emitting diode efficiency parameters. Sequential (spin coating) deposition is used for highly reproducible and dense film morphology of MAPbBr3 thin-film. In this fabrication process using an orthogonal solvent approach, control of morphology, coverage, thickness, and optical properties in these compact thin-films is demonstrated. Optical studies show direct correlation between morphology to dynamics of photoluminescence (PL) and absolute PL yield. Perovskite light emitting diodes (PeLEDs) are fabricated from these films to find the best ratio of PbBr2 versus MABr for optimal performance. This study demonstrates PeLEDs with high brightness, ≈1050 cd m−2 at 4.7 V (luminance efficiency ≈0.1 cd A−1), for optimal thin-film process with state-of-the-art device performance. This quantitative analysis suggests that these state-of-the-art PeLEDs suffer from poor charge carrier balance (≈2%) and out-coupling efficiency (≈6%). Interestingly, charge carrier balance and PL yield together can explain the change in PeLED efficiency modulation with film morphology. Studies on single carrier devices show that these PeLEDs are electron current dominated and charge carrier balance increases with operating bias voltage.

CoFe2O4 and CoFe2O4‐SiO2 Nanoparticle Thin Films with Perpendicular Magnetic Anisotropy for Magnetic and Magneto‐Optical Applications

This paper presents an efficient colloidal approach to process CoFe2O4 and SiO2 nanoparticles into thin films for magnetic and magneto‐optical applications. Thin films of varying CoFe2O4‐to‐SiO2 ratios (from 0 to 90 wt%) are obtained by sequential spin coating‐calcination cycles from the corresponding nanoparticle dispersions. Scanning electron microscopy analysis reveals a crack free and nanoparticulate structure of the sintered films with thicknesses of 480–1200 nm. Results from the optical characterization indicate a direct band gap ranging from 2.6 to 3.9 eV depending on the SiO2 content. Similarly, the refractive indices and absorption coefficients are tunable upon SiO2 incorporation. In‐plane measurements of the magnetic properties of the CoFe2O4 films reveal a superparamagnetic behavior with both Co2+ and Fe3+ contributing to the magnetism. Polar Kerr measurements show the presence of a spontaneous magnetization in the CoFe2O4 and CoFe2O4‐SiO2 (with SiO2 < 50 wt%) films, pointing to magnetic anisotropy perpendicular to the substrate. The origin of this effect is attributed to the constrained sintering conditions of the nano­particulate film and the negative magnetostriction of CoFe2O4.