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In order to develop high strength Mg-Gd-Y-Zn alloys, key experiments coupled with CALPHAD (CALculation of PHAse Diagrams) calculations were carried out in the current work to provide critical understanding of this important alloy system. Three Mg-10Gd-xY-yZn (x = 4 or 5, y = 3 or 5, wt.%) were mapped on Mg-Gd-Y-Zn phase diagrams for phase equilibria and microstructure investigation. Electron microscopy was performed for phase identification and phase fraction determination in as-cast and solution treated conditions. In all three alloys, the major phases were Mg-matrix and long period stacking order (LPSO) 14H phase. With ST at 400 and 500 °C, the phase fraction of LPSO 14H increased, particularly the fine lamellar morphology in the Mg matrix. The as-cast and 400 °C Mg10Gd5Y3Zn samples had Mg5(Gd,Y) present. At 500 °C, Mg5(Gd,Y) is not stable and transforms into LPSO 14H. The Mg10Gd5Y5Zn alloy included the W-Phase, which showed a reduction in phase fraction with solution treatment. These experimental results were used to validate and improve the thermodynamic database of the Mg-Gd-Y-Zn system. Thermodynamic calculations using the improved database can well describe the available experimental results and make accurate predictions to guide the development of promising high-strength Mg-Gd-Y-Zn alloys.

Austenitic stainless steels resist solidification cracking much better if ferrite (δ), not austenite (γ), is the primary solidification phase, but why? The curve of temperature T vs. fraction of so...

Siloles are one of the most promising building blocks for the construction of functional materials that exhibit potential application in organic photovoltaic. In the present work, two novel organic dyes featuring highly conjugated and planar tetrathienosilole (TTS) as π-bridge have been successfully synthesized and employed in dye-sensitized solar cells (DSSCs) for the first time. For comparison, dye W13 with non-rigidified 2,2′-bithieno[3,2-b]thiophene linker was prepared as well. The effects of π-bridge rigidification upon the optoelectronic properties as well as the charge transfer energetic and kinetic features of these dyes have been systematically researched. It was found that a significant enhanced open-circuit voltage had been displayed for TTS-based sensitizers as the rigidification of π-bridge with tetrahedral silicon atom. Moreover, the energy levels alignment of the dyes could be fine-tuned through modulating the electron-donating groups to optimize the dyes regeneration process. Under AM 1.5G irradiation, the devices fabricated by W15 employing [Co(phen)3]2+/3+ electrolyte achieve the highest power conversion efficiency of 8.10%, which is about 19% higher than that of W13, demonstrating the great potential of TTS spacer for constructing highly efficient organic sensitizers for DSSCs.

Most organic hole-transport materials (HTMs) toward efficient perovskite solar cells (PSCs) thus far still rely on methoxytriphenylamine, which limits the photovoltage and decrease the stability of PSCs. However, alternative donors with better performance are scarce. Herein, we employ the synergistic strategy to modulate the properties of triarylamines (TAAs) by introducing different functional groups on their outer/inside arm. It is found that the arm modulation of asymmetrical TAAs can balance well the hole transport, HOMO level, film quality and stability of the studied HTMs M140 and M141. The photovoltaic performances of devices with doped and dopant-free M140 and M141 have been investigated. Encouragingly, the doped M141 device featuring the N-(9,9-dimethyl-9H-fluoren-2-yl)-N-(4-methoxyphenyl)spiro[fluorene-9,9′-xanthen]-2-amine (MP-F-SFX) asymmetrical TAA achieves a significantly boosted power conversion efficiency (PCE) of 20.74%, accompanied by long-term stability in ambient air. This work not only provides a promising donor candidate (MP-F-SFX), but also reveals an effective way of using rationally designed asymmetrical triarylamines to fine-tune the properties of linear D–π–D HTMs.

Methoxy-free donors are an emerging class of alternative methoxy triphenylamine materials toward stable organic hole-transporting materials (HTMs). However, low cost, stable and efficient methoxy-free donors are scarce. Moreover, the lack of a molecular design strategy limits the further development of methoxy-free donor-based HTMs. This study reports a newly developed low cost hybrid methoxy-free donor (viz., indeno[2,1-b]carbazole) as well as a triple π-bridge strategy to enhance the performance of methoxy-free donor-based HTMs. Based on this strategy, two new indeno[2,1-b]carbazole HTMs, termed M136 and M138, were tailor-made and tested in perovskite solar cells (PSCs). Upon incorporating the triple π-bridges (i.e. thiophene-dithieno[3,2-b:2′,3′-d]pyrrole-thiophene and thiophene-3,4-ethylenedioxythiophene-thiophene), the resulting indeno[2,1-b]carbazole HTMs (M136 and M138) exhibit a significantly increased hole mobility, improved charge extraction and minimized trap-assisted recombination as compared to M135 and M137 with unitary and binary bridges, respectively. Consequently, the optimized devices based on M138 achieved an efficiency of 21.37%, which is among the top efficiencies for PSCs based on methoxy-free donor HTMs. The findings demonstrate that indeno[2,1-b]carbazole is an excellent methoxy-free donor. In addition, this work underscores the effectiveness of π-bridge engineering to improve the performance of methoxy-free donor-based HTMs.

The explored p–i–n inverted architecture perovskite solar cells (i-PSCs) show promising application in flexible, large-scale and laminated photovoltaic technology. Polymeric HTMs for i-PSCs have been rarely reported. Thus far, only a commercial hole-transporting material, polytriarylamine (PTAA), has achieved a significant PCE of over 23% in i-PSCs. However, a perovskite precursor exhibits poor wettability on the PTAA films, thereby reducing their reproducibility and causing uncontrollable device instability. In this study, a type of binaphthyl-ether based polymer Z13 was developed through radical polymerization to replace the palladium catalyzed coupling reaction. A small molecule (Z5) and commercial PTAA were classified as the control. The comparatively flexible ether bond (–O–) of the backbone in Z13 improved the solubility and film forming properties of the material, thereby contributing to a superior morphology uniformity of the deposited perovskite. Consequently, promising device performance was achieved for i-PSCs endowed with Z13. The maximum power conversion efficiency of 18.80% obtained for Z13 was comparable with that of PTAA (19.02%), exceeding that with Z5 (18.48%). More importantly, Z13 films ensured a significantly optimized device thermal-durability as opposed to references PTAA and Z5. This study proposed a promising design for novel polymeric materials with low costs, high production reproducibility, favorable solubility and excellent optoelectronic properties.

In this work, a comprehensive study on the deliberate molecular design and modifications of electron donors is carried out to elucidate correlations between the methoxy effects and donor configuration of hole-transporting materials (HTMs). Our initial findings demonstrate the donor-dependent methoxy effects. Photovoltaic performance of the HTM with twisted donor highly depends on the methoxy substituent. In contrast, efficiency's reliance on methoxy is insignificant for the HTM with planar donor. The HTM (M123) featuring the methoxy‑substituted carbazole shows a decent power conversion efficiency of 19.33% due to synergistic effects from both planar structure and methoxy. This work gives a guideline to access HTMs reaching both high-performance and good stability.

The mismatch of the energy level between electron transport layer (ETL) and perovskite film (PS) is one of the origins of current-voltage (J-V) hysteresis in perovskite solar cells (PSCs). Drift-di...

In this work, grain boundary (GB) potential barrier ( Δφ GB), dopant density (Pnet), and filled trap state density (PGB,trap) were manipulated at the nanoscale by exposing the fabricated perovskite films to various relative humidity (RH) environments. Spatial mapping of surface potential in the perovskite film revealed higher positive potential at GBs than inside the grains. The average Δφ GB, Pnet, and PGB,trap in the perovskite films decreased from 0% RH to 25% RH exposure, but increased when the RH increased to 35% RH and 45% RH. This clearly indicated that perovskite solar cells fabricated at 25% RH led to the lowest average GB potential, smallest dopant density, and least filled trap states density. This is consistent with the highest photovoltaic efficiency of 18.16% at 25% RH among the different relative humidities from 0% to 45% RH.

Cracking during solidification is a complex phenomenon which has been investigated from various angles for decades using both experimental and theoretical methods. In this paper, cracking susceptibility was investigated by a simulation method for three series of aluminum alloys: AA2xxx, AA6xxx, and AA7xxx alloys. The simulation tool was developed using the CALPHAD method and is readily applicable to multicomponent alloy systems. For each series of alloys, cracking susceptible index values were calculated for more than 1000 alloy compositions by high-throughput calculation. Cracking susceptible maps were then constructed for these three series of aluminum alloys using the simulated results. The effects of major and minor alloying elements were clearly demonstrated by these index maps. The cooling rate effect was also studied, and it was concluded that back diffusion in the solid can significantly improve the cracking susceptibility.

In this work, methylammonium lead triiodide (CH3NH3PbI3) perovskite solar cells with efficiencies higher than 18% were achieved using a new nanocomposite hole transport layer (HTL) by doping poly(ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) with a mixed dopant of polyaniline (PANI) and graphene oxide (GO). A synergistic engineering between GO, PANI, and PEDOT:PSS was accomplished to introduce additional energy levels between perovskite and PEDOT:PSS and increase the conductivity of PEDOT:PSS. Kelvin probe force microscope results confirmed that adding GO to PEDOT:PSS/PANI composite significantly reduced the average surface potential. This increased the open circuit voltage (Voc) to 1.05 V for the GO/PEDOT:PSS/PANI nanocomposite perovskite solar cells from the pristine PEDOT:PSS (Voc = 0.95 V) and PEDOT:PSS/PANI (Voc = 0.99 V). In addition, adding PANI to the HTLs substantially enhanced short circuit current density (Jsc). This was supported by the current sensing‐atomic force microscopy (CS‐AFM) and conductivity measurements. The PANI doped films showed superior electrical conductivity compared with those without PANI as indicated by CS‐AFM results. PANI can fill the gaps between the microflakes of GO and give rise to more compact hole transport material (HTM) layer. This led to a higher Jsc after doping with PANI, which was consistent with the incident photon‐to‐current efficiency and electrochemical impedance spectroscopy results. The results of X‐ray diffraction (XRD) and AFM indicated the GO/PANI doped HTMs significantly improved the crystallinity, topography, and crystal size of the perovskite film grown on their surface. A higher efficiency of 18.12% for p‐i‐n perovskite solar cells has been obtained by adding the mixed dopant of GO, PANI, and PEDOT:PSS, demonstrating better stability than the pristine PEDOT:PSS cell.

With perovskite-based solar cells (PSCs) now reaching efficiencies of greater than 20 %, the stability of PSC devices has become a critical challenge for commercialization. However, most efficient hole-transporting materials (HTMs) thus far still rely on the state-of-the-art methoxy triphenylamine (MOTPA) donor unit in which methoxy groups usually reduce the device stability. Herein, a carbazole-fluorene hybrid has been employed as a methoxy-free donor to construct organic HTMs. The indeno[1,2-b]carbazole group not only inherits the characteristics of carbazole and fluorene, but also exhibits additional advantages arising from the bulky planar structure. Consequently, M129, endowed with indeno[1,2-b]carbazole simultaneously exhibits a promising efficiency of over 20 % and superior long-term stability. The hybrid strategy toward the methoxy-free donor opens a new avenue for developing efficient and stable HTMs.

Bulky rigid substituents, featuring distinctive steric configuration and interesting electronic properties, play an important role in advancing performance of metal-free sensitizers toward dye-sensitized solar cells (DSSCs). However, the question about how to choose the relative position of bulky substituent for optimum device performance remains unclear, which necessitates understanding the structure-property relationship of organic sensitizers. In this work, two new isomeric dyes, W09 and W10, are designed to study the role of bulky rigid truxene unit which locates at the π-bridge and electron-donor, respectively. The comparative effects of truxene position on the optical properties, interfacial kinetic parameters and their synergistic contribution to the photovoltaic performance have been systematically investigated. A significantly improved molar absorption coefficient accompanied with a larger driving force for dye regeneration is obtained for W10 relative to those of W09, manifesting the effect of changing the truxene location. Combined with the slower charge recombination kinetics at the TiO2/dye/electrolyte interface, W10 sensitized solar cells exhibit the highest conversion efficiency of 7.62%, which is around 20% higher than that of W09. This work has demonstrated the feasibility of judiciously locating bulky rigid substituents into the right position to construct highly-efficiency metal-free sensitizers.

Deeply understanding of the performance discrepancy of hole-transporting materials (HTMs) in perovskite solar cells (PSCs) with different configuration (inverted or direct) is important for designing efficient HTMs. Herein, three organic HTMs TZ1, TZ2, and TZ3 have been employed to fabricate the inverted PSCs. Optoelectronic properties and photovoltaic performance of these HTMs are investigated. TZ3 featuring the 3,6-di(thiophen-2-yl)thieno[3,2-b]thiophene conjugate bridge shows a higher work function and enhanced capability of hole extraction, achieving a higher power conversion efficiency (PCE) of 16.33% in the inverted PSCs. Importantly, results reveal that the conjugate bridge has a relevant effect on the photovoltaic performance of cells with different device configuration. The PCE trend of TZ1, TZ2, and TZ3 in inverted PSCs is diametrically opposed to that of direct devices. We proposed that linear triphenylamine HTMs contain a fused bridge with high degree of conjugation are good choice for the direct PSCs. On the other hand, it is better to incorporate linear triphenylamine HTMs with deep highest occupied molecular orbital (HOMO) toward the inverted PSCs, because the photovoltage plays a crucial role in the efficiency of the inverted PSCs. This systematic study provides a new viewpoint to design HTMs toward PSCs with different device configuration.

In this work, four new truxene-based hole-transporting materials (HTMs) have been synthesized and applicated in the inverted perovskite solar cells (PSCs). The impact that the length of alkyl and periphery arylamine on the photophysical, electrochemical and hole transporting properties has been systematically investigated. These new HTMs exhibit decent hole mobility of 10−3 cm2 V−1 s−1, which ensure efficient hole extraction in dopant-free devices. PSC using the dopant-free M118 achieves a power conversion efficiency of 17.1%, which is much higher than the value of 14.4% achieved using poly (3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). Importantly, PSCs based on these truxene HTMs exhibit significantly enhanced durability under UV light. This work reveals that the adjustment of length of alkyl as well as periphery arylamine is necessary for development of stable and efficient truxene HTMs.

A self-consistent thermodynamic description of the Zn–Al–Cu–Mg quaternary alloy system is developed. The as-cast microstructures of key Zn–Al–Cu–Mg samples in the low-alloyed range are studied experimentally. These are interpreted by computational thermodynamic analysis applying both Scheil and equilibrium simulations. Contradictions concerning the variation of apparent fraction of primary (Zn) phase, the eutectic structure and visibly larger fractions of eutectoid structure with increasing Mg content can be resolved by these detailed calculations. Two series of dedicated experimental work found in this journal on as-cast microstructures of such quaternary Zn alloys in the high-alloyed range, including also thermal analysis data, were also analyzed. The viability of this computational thermodynamic approach is demonstrated by providing a detailed analysis going beyond the explanations and interpretations in the original publications. The coverage of a larger Zn alloy composition range suggests a predictive capability of this approach.

The phase equilibria and thermodynamic properties of the Zn-Ti system have been investigated by experiments, first-principles calculations and Calphad assessment. Differential scanning calorimetry measurement and microstructure characterization confirmed the Zn richest eutectic reaction to occur at 691.3 ± 0.4 K with about 0.27 at% Ti in the liquid. Density functional theory (DFT) calculations have been performed to calculate the finite-temperature heat capacity (Cp) of the intermetallics, providing also the absolute entropies. A full thermodynamic assessment of the Zn-Ti system has been performed by using the experimental and DFT results obtained in this work together with the collection of all available data from previous publications. In the present work, the Calphad results show good agreement not only in thermodynamic properties with DFT data, but also phase equilibria data with experimental results, especially in the Zn-rich side, which significantly improved from previous Calphad assessment. Phase diagrams including the gas phase have also been calculated and discussed.

Judicious design alkyl side chain decorated fused aromatic heterocycles as π-spacers has proved to be an efficient strategy to construct highly efficient organic sensitizers. Three novel metal-free dyes W02–04 featuring a highly planar and extensively conjugated 9H-thieno[2′,3':4,5]thieno[3,2-b]thieno[2′,3':4,5]thieno[2,3-d]pyrrole (TTTP) π-bridge have been successfully constructed and applied in dye-sensitized solar cells (DSSCs) for the first time. To better understand the TTTP bridge, the dye W01 possessing the nonplanar 3-hexylthiophene-dithieno[3,2-b:2′,3′-d]pyrrole-3-hexylthiophene linker is prepared as a reference. Introduction of TTTP bridge into the dyes skeleton notably enhances the molar extinction coefficients (e) by comparison with the reference dye, and much improved short-circuit current (Jsc) have been realized. Meanwhile, dynamics measurements reveal that the charge recombination in devices has been significantly reduced by the incorporation of TTTP bridge. Among these dyes, the DSSCs fabricated with W03 employing cobalt electrolyte achieves an excellent power conversion efficiency of 9.43%, with open-circuit voltage (Voc) of 848 mV, Jsc of 16.2 mA cm−2, and fill factor of 0.70 under simulated AM 1.5 G conditions. This work provides important new insight into designing novel organic sensitizers with high e and efficient suppression of charge recombination.

We have synthesized two non-linear molecules with Y-shaped (XSln847) and X-shaped (XSln1453) structures via a facile synthetic route. Comparable to an X-shaped structure, the Y-shaped structural backbone of XSln847 enables a tight molecular stacking arrangement through multiple intermolecular short contacts, which affords a nest-layer in molecules. As a result, the pristine, Y-shaped XSln847 gives higher hole-mobility and more effective photoluminescence quenching than does XSln1453. Additionally, a decreased charge recombination occurs in the XSln847-fabricated inverted perovskite solar cells. As a consequence, the device based on XSln847 affords a higher power conversion efficiency of 15.02% than does that of XSln1453 (12.65%) under standard global AM 1.5 illumination. The efficiency is further improved to 17.16% when using XSln847 doping with 2, 3, 5, 6-tetrafluoro- 7, 7, 8, 8-tetracyanoquinodimethane, which is much higher than that of the widely-used PEDOT:PSS (11.95%) when measured under the same condition. These results demonstrate that the molecular engineering of hole transport materials with non-linear structure is a promising strategy for designing efficient molecules for inverted perovskite solar cells.

Novel binaphthylamine-based hole-transport molecules with different side-chains were designed and synthesized. The obtained materials exhibit comparable optoelectronic properties and molecular configuration, but distinct film properties. In this work, which was inspired by the structural feature of polymer and π–π stacking strategy of carbon nanotubes with large π-spacers, two kinds of optimized hole-transport molecules with amine and methyl units were attached to multi-walled carbon nanotubes by physisorption, and were further used to fabricate inverted perovskite solar cells. A non-encapsulated device based on a hole-transporting material with multi-walled carbon nanotubes gives a power conversion efficiency of 17.17%, comparable to that of the pristine hole-transport material (17.32%). More importantly, the former exhibits a higher device stability than the later. Introduction of carbon nanotubes to hole-transport materials provides a new method for improving the device stability of inverted perovskite solar cells.

A photoanode fabricated with agglomerated zinc stannate nanoparticles was applied to dye sensitized solar cells (DSCs) based on cobalt complex mediators. The resultant devices yield an impressive power conversion efficiency of 8.1% under 100 mW cm-2 (AM1.5) light irradiation, which demonstrates the feasibility of use of zinc stannate photoanodes in iodine-free DSCs.

A complete thermodynamic description of the Mg-Ca-O system and phase diagrams is developed. It is based on our extensive thermodynamic analysis of solid CaO and MgO data and validation of the low-temperature Mg-Ca-O phase diagram up to 1050 K. This work presents the high- temperature oxygen solubilities and revisions of calculated melting points of the oxides. An extension of the empirical schemes for predicting the activity coefficient of oxygen in liquid elements is proposed to predict data for the Mg-O system. Consistent thermodynamic descriptions of the complete binary Ca-O and Mg-O systems are developed. It is shown that this framework is crucial to understand recently measured significantly different melting points of CaO under oxidizing versus reducing conditions. The revised description of the MgO-CaO quasibinary oxide system considers all experimental data, revealing significantly different melting equilibria compared to all previous publications.

Diphenylamine-substituted carbazole (DPACZ) compounds are one of the most interesting hole-transporting materials (HTMs) for perovskite solar cells (PSCs). However, most studies focused on the development of symmetrical DPACZ HTMs with two DPACZ arms or multiple ones. In this work, we developed a new class of asymmetric DPACZ-based HTMs (M111–114) through a combination of one DPACZ arm and different S,N-heterocyclic compounds (phenothiazine (PTZ) and dithieno[3,2-b:2′,3′-d]pyrrole (DTP)), which endow the M111–114 with different electrochemical and photophysical properties as well as hole-transporting properties. Results conclude that the PTZ outperforms of the DTP when combined with the DPACZ arm. In addition, we have investigated the substituent and conjugation effects of heterocyclic properties on the photophysical and electrical properties, as well as performance in PSCs by using physical measurements. PSCs with M114 exhibit a power conversion efficiency of 17.17%, which is higher or comparable to that...

The property of charge extraction at the contact between the perovskite and electron selective layer (ESL) is vital to the photovoltaic performance of perovskite solar cells (PSCs). The J–V hysteresis phenomenon is frequently observed when the PSC is limited by inefficient charge transfer across the perovskite/ESL interface. Drift–diffusion simulations are performed so as to correlate the hysteresis with the quality of the perovskite/ESL junction. A generalized charge exchange model is introduced into drift–diffusion equations for describing the dynamics of charge extraction at the perovskite/ESL contact. Our simulations demonstrate that inefficient charge extraction is one of the causes of j–V hysteresis. This is because limited charge transfer gives rise to a depletion domain in the ESL, and hence promotes the interfacial accumulation of charge carriers as well as movable ions. Furthermore, it is found that the incorporation of surface recombination into drift–diffusion simulations enables the loss in open circuit voltage to be simulated in PSCs with different charge transfer properties. The simulation results indicate that j–V hysteresis can be suppressed by improving the charge extraction property and suppressing surface recombination.

Some published experimental results on the thermodynamic data of pure solid CaO and MgO significantly contradict the widely used data in review books or tables, such as JANAF data. We scrutinized all the original experimental data forming the basis in review books and tables in order to establish a more realistic uncertainty range. The two Gibbs energy functions of CaO and MgO are combined with those of all other relevant phases to develop a thermodynamic database for the Mg–Ca–O system. The first systematic study of the calculated Mg–Ca–O phase diagram is presented. This phase diagram is validated by recently obtained dedicated experimental data using in-situ synchrotron radiation diffraction to study phase formation and reactions during melting and solidification of Mg and Mg–Ca alloys with CaO-additions below 1050 K. Intricacies in the solidification path of Mg-rich ternary alloys are revealed by the present thermodynamic calculations. Mg-rich alloys are categorized in four groups according to their participation in different invariant four-phase reactions. The development of non-equilibrium constitution of four phases, (Mg) + Mg2Ca + MgO + CaO, in the fully solidified sample is explained.

Dithieno[3,2-b:2′,3′-d]pyrrole (DTP) derivatives are one of the most important organic photovoltaic materials due to better π-conjugation across fused thiophene rings. In this work, two new hole transport materials (HTMs), H16 and H18, have been obtained through a facile synthetic route by cross linking triarylamine-based donor groups with a 4-(4-methoxyphenyl)-4H-dithieno[3,2-b:2′,3′-d]pyrrole (MPDTP) and N-(4-(4H-dithieno[3,2 b:2′,3′-d]pyrrol-4-yl)phenyl)-4-methoxy-N-(4-methoxyphenyl)aniline (TPDTP) unit, respectively. The H16 HTM outperforms the H18 in terms of conductivity, hole mobility, and hole transport at the interface. This result could be attributed to the enhancement of the conductivity, hole mobility and high quality of the film exerted by the MPDTP core. The optimized device based on H16 exhibits a high power conversion efficiency (PCE) of 18.16%, which is comparable to that obtained with the state-of-the-art-HTM spiro-OMeTAD (18.27%). Furthermore, the long-term aging test shows that the H16 based device has good stability after two months of aging under controlled (20%) humidity in the dark. Importantly, the synthesis cost of H16 is roughly 1/5 of that of spiro-OMeTAD. The present finding highlights the potential of DTP based HTMs for efficient PSCs.

First results on the constitution of the ternary systems Li-Sn-C and Li-Sn-Si are presented. Extrapolation calculations from the binary boundary systems allow identifying three alloys with key compositions that yield substantial information about the ternary phase diagrams. These alloys were characterized after long-term annealing using X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The XRD and DSC measurements suggest the formation of a solid solution of the isostructural phases Li5Sn2 and Li7Si3 instead of predicted three phase equilibrium in the Li-Sn-Si system. Ternary phases are not observed.

Hole-transporting materials (HTMs) play a crucial role in achieving highly efficient and stable perovskite solar cells (PSCs). Currently, the vast majority of HTMs reported are applicable only for either n-i-p structured regular cells (r-PSCs) or p-i-n structured inverted devices (i-PSCs) (e.g. Spiro-OMeTAD shows an impressive efficiency in r-PSCs, while a poor performance was observed in i-PSCs). The restricted application of HTMs greatly causes waste of materials and increases the research cost of photovoltaic devices, which is harmful to industrial large-scale application and sustainable development. Here, we provide an effective and efficient approach to improve the performance of both r-PSCs and i-PSCs using HTM (PI-2) featuring with a phenanthro[9,10-d]imidazole core via rational π-extension and lower symmetry. The other HTM, DI-1, using non-hybrid imidazole as the central core, was designed as control. Comparing with DI-1, the coplanar π-extended phenanthro[9,10-d]imidazole based PI-2 endows enriched intermolecular interactions as well as enhanced π-π stacking, thus achieving a higher hole mobility. It also exhibits matched energy levels and high thermal stability for application in PSCs. Moreover, a decreased symmetrical conformation of PI-2 contributes to an amorphous film with superior morphological uniformity. Consequently, the p-i-n structured devices with PI-2 realize a champion power conversion efficiency (PCE) of 19.11% and the n-i-p structured devices based on PI-2 achieve an encouraging champion PCE of 21.65%, representing one of the best results among universal HTMs in both i-PSCs and r-PSCs.

Investigations on the thermodynamics of alloy-type anode materials have been carried out for the quaternary Li–C–Si–Sn system. Phase equilibria and phase stabilities were characterized in the binary subsystems Li–C, Li–Si, Li–Sn. The Calphad method was first used to optimize or completely re-establish all binary subsystems containing Li. For reasons of consistency, the binary subsystem Si–C had to be revisited and its Calphad description was modified. The ternary phase diagrams were then tentatively calculated by extrapolation from the binary subsystems and confirmed by key experiments. No ternary compounds were found. In order to verify the applicability of the anode materials in real batteries, some of the materials were nanostructured by ball milling and spark plasma sintering, the corresponding nanostructures were characterized. Theoretical predictions that nanograined Li2C2 can also be used as cathode material were verified experimentally. The methodologies worked out in the present project (e. g. nanoscale structure transmission electron microscopy analysis, glow discharge optical emission spectroscopy) were also employed in other projects and led to publications concerning other materials such as Mg alloys, carbon nanofibers and an Mn-based antiperovskite.

Developing carbazole derivatives as the electron donor for organic dyes have attracted extensive interest recently. Three organic dyes M92-94 based on the 9-hexyl-2-(hexyloxy)-9H-carbazole (HHCBZ) electron donor have been successfully designed and synthesized for dye-sensitized solar cells. M95 with the 9-hexyl-9H-carbazole (HCBZ) unit has also been synthesized for comparison. An introduction of the HHCBZ unit in triarylamine brings several advantages: (i) red shifting the absorption peak and increasing the maximum molar absorption coefficient of absorption bands; (ii) decreasing the charge recombination in cobalt cells as well as iodine cells; (iii) enhancing photocurrent/photovoltage and thus the power conversion efficiencies of cobalt cells as well as iodine cells. Devices prepared with M92 show consistently higher light-to-electric energy conversion efficiencies, with the champion device reaching 8.67%, surpassing M93-95.

The formation of single disordered solid solution phase in multi-principal element alloys (MPEAs) is crucial for the properties of the alloy, and thus several empirical rules have been proposed to predict the stability of disordered solid solution phase in MPEAs. Compared to these empirical rules, Calphad approach provides a more reliable and quantitative prediction. In the present work, we choose three model systems of Al x CoCrFeNi, CoCr x FeMnNi and Al x LiMgSnZn to evaluate these empirical rules by comparing with the Calphad calculated results. The Calphad calculated temperature-composition sections reveal the effect of composition on the phase formation under equilibrium condition. Corresponding diagrams along these sections illustrate parameter variations from empirical rules associated with alloy compositions and highlight predictions and limitations. The impact of the different sources of atomic size data is also discussed.

A consistent thermodynamic description of the Li-Si system and its extension to the Li-Si-H system is developed based on comprehensive Calphad-type assessment of all pertinent thermodynamic and phase equilibrium data. Key experiments were performed by measuring the equilibrium pressure for the hydrogenation of the lithium silicides at 773 K, 748 K and 723 K. The Gibbs energy functions of the Li-Si compounds developed in this work are validated by direct comparison of the predicted hydrogen pressure with experimental data. The interrelation of the hydrogen absorption pressure with the calculated Li-Si-H ternary phase diagram is also elucidated. The calculated Li-Si phase diagram, both on chemical potential and composition scale, is well supported by the entity of experimental data. In addition to the stable intermetallics Li17Si4, Li16.42Si4 (Li4.11Si), Li13Si4, Li7Si3, Li12Si7, LiSi also metastable Li15Si4 and an approximate for amorphous Si(Li) is included in the thermodynamic modeling. Qualitative prediction of open-circuit voltage curves during metastable lithiation/delithiation of Si as advanced anode material for Li-ion batteries at room temperature is made.

New star-shaped and efficient hole-transporting materials based on a 1,1′-bi-2-naphthol central core for perovskite solar cells are developed via facile synthesis. The 1,1′-bi-2-naphthol is first applied into the field of perovskite solar cells. The 2,7-carbazole-bis(4-methoxy-phenyl)-amine and 3,6-carbazole-bis(4-methoxy-phenyl)-amine are used as end groups. A reference compound based on a 3,3′-biphenyl core is prepared as well. The new materials have suitable highest occupied molecular orbital levels to match well with the valence band of CH3NH3PbI3, and they all exhibit a glass transition temperature higher than 160 °C. A device fabricated by hole-transporting materials based on 1,1′-bi-2-naphthol and 2,7-carbazole-bis(4-methoxy-phenyl)-amine in conjunction with a carbon counter electrode achieves the highest power conversion efficiency of 8.38% under the illumination of 100 mW cm−2, which is comparable to that fabricated by commercial spiro-OMeTAD (8.73%). Dark current, IPCE and IMVS measurements are also discussed. The introduction of 2,7-carbazole-bis(4-methoxy-phenyl)-amine onto the 1,1′-bi-2-naphthol central core tends to enhance Jsc of a device, and 3,6-carbazole-bis(4-methoxy-phenyl)-amine improves Voc. This work provides a new series of hole-transporting materials to fabricate economic and efficient perovskite solar cells.

The thickness of TiO2 film is vital to realize the optimization on photovoltaic performance of dye sensitized solar cells (DSSCs). Herein, the process of charge separation in DSSCs was simulated by using a drift-diffusion model. This model allows multiple-trapping diffusion of photo-generated electrons, as well as the back reaction with the electron acceptors in electrolyte, to be mimicked in both steady and non-steady states. Numerical results on current-voltage characteristics allow power conversion efficiency to be maximized by varying the thickness of TiO2 film. Charge collection efficiency is shown to decrease with film thickness, whereas the flux of electron injection benefits from the film thickening. The output of photocurrent is actually impacted by the two factors. Furthermore, recombination rate constant is found to affect the optimized film thickness remarkably. Thicker TiO2 film is suitable to the DSSCs in which back reaction is suppressed sufficiently. On the contrary, the DSSCs with the redox couple showing fast electron interception require thinner film to alleviate the charge loss via recombination. At open circuit, electron density is found to decrease with film thickness, which engenders not only the reduction of photovoltage but also the increase of electron lifetime.

To explore the behavior of radiolytically produced hydrogen release from the waste resin stored in a high integrated container (HIC), and the mechanism of hydrogen diffusion in a near-surface disposal facility, both experimental studies and numerical simulations were performed through an accelerated irradiation test and simulated disposal, respectively. Results indicated that, 100 years after disposal, the highest hydrogen concentration appeared in the cell where the HICs were placed. The volume fraction for different scenarios postulated in the numerical simulation was 2.64% for Scenario 1, 2.28% for Scenario 2, and 3.965% for Scenario 3, all of which are lower than the hydrogen explosion limit of 4.1%. The results indicated that the simulated HIC disposal scheme is safe.

The behavior of Li-ion batteries is explained on the basis of phase diagram and thermodynamics. Calculation of phase diagram (Calphad) technique is introduced and applied for obtaining reliable thermodynamic models of corresponding material systems. Si and Sn as well as mixed conductor Si-Sn alloys are selected as example anode materials. LiMn2O4 spinel cathode is used to explain behavior of the cathode side. Finally, operating voltages of an imaginary battery series composed of Si-Sn mixed conductor anodes and LiMn2O4 spinel cathodes are shown using calculated results obtained with established thermodynamic models.

Construction of di-anchoring organic sensitizers has been recently recognized as an effective strategy to develop high-efficiency dye-sensitized solar cells (DSSCs). However, the relatively low open-circuit photovoltage (Voc) for di-anchoring dyes have become to be the bottle-neck for further advancing the photovoltaic performance. In this work, two novel L(D-π-A)2 type di-anchoring sensitizers, W11–W12, featuring 9H-thieno[2′,3':4,5]thieno[3,2-b]thieno[2′,3':4,5]thieno[2,3-d]pyrrole (TTTP) as π-conjugated spacer, have been developed and well examined for a systematical study of the structure-property relationship of these dyes. Through the rational adjustment of donor-linking bridges, carbazole decorated W12 exhibits dramatically enhanced light-harvesting efficiency as well as self-anti-aggregation ability with respect to those of W11 employing triphenylamine linkage. More importantly, a compact arranged organic layer benefiting from the superior dye-loading amounts has been formed for W12, which is beneficial to keep the oxidized electrolyte from the TiO2 surface, thus bringing forth more efficient suppression of interfacial charge recombination and consequently higher Voc values. Under standard AM 1.5 G illumination, DSSCs sensitized by W12 employing [Co(phen)3]2+/3+ electrolyte display a fascinating power conversion efficiency as high as 8.28%, with an impressive open-circuit voltage (Voc) of 847 mV, which is among the highest cells efficiencies of L(D-π-A)2 type di-anchoring organic dyes.

Proton exchange membrane fuel cell (PEMFC) mainly relied on the modeling analysis of the traditional numerical method. However, the scale of the research is bigger than porous medium layer of the particle that can’t meet the actual mechanism of the simulation. Hence, as a new mesoscopic numerical method, Lattice Boltzmann method (LBM) builds a model based on the microstructure and analyzes the dynamics, while the transfer state of the porous media layer of PEMFC can be more realistically described during its actual operation.

Fused-ring thiophene compounds emerged as an important type of building blocks for organic dyes toward the dye-sensitized solar cells (DSSCs) because of their good charge transfer and light-harvesting properties. Nevertheless, some fused-ring thiophenes have a lack of desired alkyl chains or side alkyl chains, which may induce a severe charge recombination in devices. In this work, the hex-1-en-1-ylbenzene (HEYB) unit was introduced in two new fused-ring thiophene organic dyes (M60 and M59), resulting in a modest dihedral angle (∼36°) between the donor and spacer in dyes. The effect of the HEYB unit on optical, electrochemical, and photovoltaic properties has been investigated by comparing with their congeners (M42 and M58) without the HEYB unit. It is found that introduction of the HEYB unit in arylamine donor enhanced the driving force for dye regeneration and beneficial for suppressing dye aggregation as well as reducing the charge recombination. Device performance characteristics demonstrate that intr...

In this paper, chip recycled pressing process (CRP for short), a new method for recycling magnesium alloy chips, was put forward to prepare semi-solid billet. AZ91D magnesium alloy chips of different sizes were respectively recycled to prepare semi-solid billet by CRP process. Effect of chip size on compactness, microstructure and oxidation of CRP billet were investigated. And then CRP billet were heated to semi-solid state and its semi-solid microstructures were studied. The results showed that with the increase of chip thickness, grain refinement effect weakened, deformation uniformity aggravated and oxygen content of CRP billet decreased. Under the same CRP process conditions, the relative densities of four kind of CRP billet were 98.27%, 98.13%, 98.05% and 97.92%, respectively. Meanwhile, there was no significant difference in compactness and microstructure between them. Normally, oxygen content was not more than 1.8% and uniformly dispersed in CRP billet. Hence, the influence of size and deformation inhomogeneity of chip on compactness and microstructure of CRP billet were eliminated via CRP process. In CRP billet, microstructure and strain were uniform and this inherited during semi-solid isothermal treatment.

Three new dithieno[3,2-b:2′,3′-d]pyrrole units (DTPA1–3) based on the truxene core have been designed and synthesized for a potential application in photovoltaic cells. One of these units (DTPA1) has been employed to construct a new organic dye (M47), exhibiting a higher solar-to-electrical energy conversion efficiency when compared to reference dyes (M48 and M49) under the same conditions. Absorption spectra, electrochemical cyclic voltammetry, theoretical calculations, current voltage curves and controlled intensity modulated photovoltage spectroscopy have been investigated. M47 sensitized solar cells employing a cobalt electrolyte afford a short circuit photocurrent of 12.1 mA cm−2, an open circuit voltage of 758 mV, and a fill factor of 0.56, corresponding to an overall power conversion efficiency of 5.1% under standard AM 1.5 sunlight. These results suggest that the truxene-substituted dithieno[3,2-b:2′,3′-d]pyrrole derivatives are promising candidates for photovoltaic cells.

Developing effective hole-transporting material is critical to achieve high efficiency CH 3 NH 3 PbI 3 perovskite solar cells. A new thermal-stable truxene-based material, 2,7,12-tri(N,N-di(4-methoxyphenyl)amino)-5,5′,10,10′,15,15′-hexapropyltr-uxene, has been synthesized by a facile route. A reference compound, 1,3,5-tris(di-p-anisylamino)benzene, was prepared as well. Their optical, electronic properties, thermal stability and photovoltaic performances were investigated. This new truxene-based material exhibits a high decomposition temperature (432 °C), a high glass transition temperature (134 °C), and a suitable highest occupied molecular orbital level well-matched with the valence band of CH 3 NH 3 PbI 3 . The device based on this new material in conjunction with a carbon counter electrode achieves a power conversion efficiency of 3.18% under the illumination of 100 mW cm −2 , which is better than that of the reference compound (0.93%). These results indicate truxene core is a promising building block for hole-transporting material.

In recent years, hybrid perovskite solar cells (HPSCs) have received considerable research attention due to their impressive photovoltaic performance and low‐temperature solution processing capability. However, there remain challenges related to defect passivation and enhancing the charge carrier dynamics of the perovskites, to further increase the power conversion efficiency of HPSCs. In this work, the use of a novel material, phenylhydrazinium iodide (PHAI), as an additive in MAPbI3 perovskite for defect minimization and enhancement of the charge carrier dynamics of inverted HPSCs is reported. Incorporation of the PHAI in perovskite precursor solution facilitates controlled crystallization, higher carrier lifetime, as well as less recombination. In addition, PHAI additive treated HPSCs exhibit lower density of filled trap states (1010 cm−2) in perovskite grain boundaries, higher charge carrier mobility (≈11 × 10−4 cm2 V−1 s), and enhanced power conversion efficiency (≈18%) that corresponds to a ≈20% improvement in comparison to the pristine devices.

The core plays a crucial role in achieving high performance of linear hole transport materials (HTMs) toward the perovskite solar cells (PSCs). Most studies focused on the development of fused heterocycles as cores for HTMs. Nevertheless, nonfused heterocycles deserve to be studied since they can be easily synthesized. In this work, we reported a series of low-cost triphenylamine HTMs (M101-M106) with different nonfused cores. Results concluded that the introduced core has a significant influence on conductivity, hole mobility, energy level, and solubility of linear HTMs. M103 and M104 with nonfused oligothiophene cores are superior to other HTMs in terms of conductivity, hole mobility, and surface morphology. PSCs based on M104 exhibited the highest power conversion efficiency of 16.50% under AM 1.5 sun, which is comparable to that of spiro-OMeTAD (16.67%) under the same conditions. Importantly, the employment of M104 is highly economical in terms of the cost of synthesis as compared to that of spiro-OMeTAD. This work demonstrated that nonfused heterocycles, such as oligothiophene, are promising cores for high performance of linear HTMs toward PSCs.

Self-assembly of organic sensitizer layers in cobalt complex-based DSCs was studied to elucidate its role in reducing the loss of charge recombination. DSCs with various dye loadings were fabricated by dye desorption without the aid of basic solvent. The FT-IR and UV results indicate the deprotonation of the anchoring organic sensitizers, which influences the conduction band of TiO2 remarkably by changing the surface potential. Positive band edge shifts and a decrease of the recombination rate constant are demonstrated to be the main factors affecting energy loss at open circuit. In contrast, absorbed photon conversion efficiency (APCE) analyses illuminate the crucial role of the packing of the anchoring sensitizer in reducing recombination loss at short circuit. This is further supported by numerical simulations, which show that APCE is primarily dependent on the recombination rate constant rather than the band edge shift at short circuit. These results highlight the importance of self-assembly of sensitizers with insulating groups in retarding charge recombination by forming overlapping molecular layers.

Even small amounts of Phosphorus and Strontium strongly affect the microstructure of hypoeutectic Al–Si alloys. P is an unavoidable trace element in commercial Al-alloys which causes formation of AlP particles as potent nucleation sites for eutectic (Si). Sr, in contrast, is purposely added to modify the morphology of eutectic (Si) towards fine coral-like fibers. It is hypothesized that Sr does not only alter the growth kinetics of (Si), but additionally prevents detrimental (Si) nucleation due to neutralization of AlP particles by Al2Si2Sr formation. This presumes that both AlP and Al2Si2Sr precipitate prior to (Si). Using a newly assessed thermodynamic database for the Al–Si–Sr–P system, critical P and Sr thresholds for pre-silicon formation of AlP and Al2Si2Sr were evaluated and mapped under equilibrium and Scheil conditions. The competitive precipitation of AlP, Al2Si2Sr and (Si) and its impact on the evolution of the eutectic morphology was further studied by 3D phase-field simulations. Effective anisotropy functions for the (Si) interface mobility considered Sr-induced internal twinning. Depending on whether subcritical or supercritical P and Sr contents were selected, either a fine lamellar structure, a coarse flaky structure, or the targeted fine fibrous eutectic structure was reproduced.

Triphenylamine (TPA) and their derivatives are well-known electron-rich compounds that are widely used in various optical and electronic fields. Here, two new organic dyes (M40 and M41) featuring TPA or dihexyloxy-substituted triphenylamine (DHO–TPA) electron donor have been designed and synthesized. M40 sensitized DSCs employing the Co(II/III)tris(1,10-phenanthroline)-based redox electrolyte affords a short circuit photocurrent of 14.32 mA cm−2, an open circuit voltage of 907 mV, and a fill factor of 0.68, corresponding to an overall conversion efficiency of 8.83% under standard AM 1.5 sunlight. This efficiency is much higher than those of the M41 sensitized DSCs, being 7.81% under the same conditions. Absorption spectra, electrochemical measurements, theoretical calculations, and photovoltaic measurements are used to compare the light absorptions, energy-levels, and charge transfer dynamics that contribute to the photovoltaic behavior.

We report two new triarylamine-cyanoacrylic acid based push–pull dyes, X76 and X77, featuring the π-conjugated linkers of dihexyl- and dihexyloxybenzene-substituted dithieno[2,3-d:2′,3′-d′]thieno[3,2-b:3′,2′-b′]dipyrrole (DTDP), respectively. The absorption, electrochemical, and photovoltaic properties for all sensitizers have been systematically investigated. Both dyes containing a DTDP moiety showed good light harvesting ability as compared to that of the reference dye incorporating the hexyl-substituted dithieno[3,2-b:2′,3′-d]pyrrole (DTP) linker. Moreover, the substituents of DTDP moiety significantly influenced the electrochemical and photovoltaic properties of the dyes. The incident photon-to-current efficiency (IPCE) of the X77-based device is higher at longer wavelengths, and extends to nearly 800 nm. A dye-sensitized solar cell employing the X77 photosensitizer and the Co-bpy electrolyte exhibits a power conversion efficiency of 6.6% measured under the 100 mW cm−2 simulated AM1.5 sunlight.