Indoor Photovoltaic Fiber with an Efficiency of 25.53% under 1500 Lux Illumination.

Photovoltaic devices represent an efficient electricity generation mode. Integrating them into textiles offers exciting opportunities for smart electronic textiles-with the ultimate goal of supplying power for wearable technology-which is poised to change how electronic devices are designed. Many human activities occur indoors, so realizing indoor photovoltaic fibers (IPVFs) that can be woven into textiles to power wearables is critical, although currently unavailable. Here, a dye-sensitized IPVF is constructed by incorporating titanium dioxide nanoparticles into aligned nanotubes to produce close contact and stable interfaces among active layers on a curved fiber substrate, thus presenting efficient charge transport and low charge recombination in the photoanode. With the combination of highly conductive core-sheath Ti/carbon nanotube fiber as a counter electrode, the IPVF shows a certified power conversion efficiency of 25.53% under 1500 lux illuminance. Its performance variation is below 5% after bending, twisting, or pressing for 1000 cycles. These IPVFs are further integrated with fiber batteries as self-charging power textiles, which are demonstrated to effectively supply electricity for wearables, solving the power supply problem in this important direction.

MOF-Assisted Annealing-Free Crystallization Technology of Perovskites toward Efficient and Stable Perovskite Solar Cells.

Although annealing is a commonly used crystallization method for perovskite films in perovskite solar cells (PSCs), the high thermal energy consumption and limitations on flexible devices hinder their further industrial application. We herein propose an annealing-free crystallization technology for perovskite films, assisted by the Zr-metal-organic framework (MOF) interface between SnO2 and the perovskite. It is found that the Zr-MOF interface can accelerate the formation of perovskite intermediates and promote their conversion into perovskite crystals even without annealing. The trap density thus decreases by about one fold, accompanied by significant increases in electron and hole mobilities, resulting in enhanced carrier extraction and suppressed charge recombination. Therefore, the Zr-MOF-based PSC attains a power convention efficiency (PCE) of 20.24%, 2.2 times that (9.26%) of the pristine PSC. Furthermore, the Zr-MOF interface layer can significantly improve the air and thermal stabilities of PSCs. The Zr-MOF-based PSC exhibits 93% of its initial PCE versus 52% for the pristine PSC after 1018 h of storage in air. Additionally, after 360 h of continuous heating at 65 °C, the Zr-MOF-based PSC retains 91% of its initial PCE against 44% for the pristine PSC.

Spiro[cyclopentadithiophene-dioxolane]-Based D-A-D Type Organic Molecule for Both Crystallization Improvement and Band Adjustment of Perovskites.

To improve the crystallization and meanwhile adjust the band levels of perovskites, we design and synthesize a novel organic molecule, 4,4'-(spiro[cyclopenta[1,2-b:5,4-b']dithiophene-4,2'-[1,3]dioxolane]-2,6-diyl)bis(N,N-bis(4-methoxyphenyl)aniline) (TM1), to dissolve in an antisolvent for the antisolvent engineering of perovskite solar cells (PSCs). The coordination interactions between TM1 and Pb2+ ions in perovskites and the hydrogen bonds between the O atoms in the methoxy of TM1 and the MA+ in perovskites are characterized with X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Owing to these interactions, TM1 can improve the perovskite crystallization, which reduces the trap density, enhances the interfacial hole extraction, and retards charge recombination as well, boosting short-circuit photocurrent notably. TM1 also shifts the valence band of perovskites upward by 0.17 eV, which aligns better with the highest occupied molecular orbital of hole transport materials and thus increases the open-circuit photovoltage significantly. As a result, the power conversion efficiency is enhanced from 17.22 to 20.21% by TM1. Moreover, TM1 can also improve device stability significantly. These findings demonstrate that TM1 is a kind of functional material as an additive in an antisolvent for both crystallization improvement and energy level adjustment of perovskites toward highly efficient and stable PSCs.

Black Phase of Inorganic Perovskite Stabilized with Carboxyimidazolium Iodide for Stable and Efficient Inverted Perovskite Solar Cells.

As all-inorganic perovskite (CsPbI3-xBrx) is prone to phase transition from the α phase (black phase) to the δ phase (yellow phase) in a humid environment or under heating, improving the phase stability of all-inorganic perovskite of the black phase is one of the urgent problems to solve. Herein, 1,2-dimethyl-3-acetylimidazolium iodide (DMAII) is spin-coated onto the surface of CsPbI3-xBrx perovskite for use in p-i-n perovskite solar cells (PSCs). We find that the DMAII coating has two effects on the CsPbI3-xBrx perovskite film: surface passivation and phase stabilization of perovskite. Traps in the CsPbI3-xBrx perovskite film can be reduced significantly by DMAII passivation, resulting in enhanced hole extraction and suppressed charge recombination. Consequently, the power conversion efficiency (PCE) is improved from 10.81 to 13.14%. Moreover, the DMAII coating can significantly inhibit the phase transition from the α phase to the δ phase in a humid environment or under heating, as characterized by the X-ray diffraction pattern, UV-vis absorption spectrum, and film color. After exposing the CsPbI3-xBrx perovskite films to a humid atmosphere (relative humidity = 40-60%) for 6 h, the PCE decreases dramatically to only 0.12% of the initial PCE for the PSC without the DMAII coating, while the PCE maintains 80% of the initial PCE for the PSC with the DMAII coating. In addition, when the PSC devices are heated at 120 °C for 4 h, the control PSC shows a 96% decrease in PCE, while the PCE decay is only 9% for the DMAII-coated PSC. These findings indicate that carboxyl-substituted imidazolium iodide is a kind of promising material to not only passivate traps but also stabilize the black phase of all-inorganic perovskite.

Highly Efficient and Stable Pure Two-Dimensional Perovskite-Based Solar Cells with the 3-Aminopropionitrile Organic Cation.

Pure two-dimensional (2D) perovskite (n = 1)-based perovskite solar cells (PSCs) have been proven to have excellent stability against humidity, but the photovoltaic performance is very poor due to the parallel orientation to the substrate and mismatched energy alignment in the PSC device. We report herein a novel bulky organic cation of 3-aminopropionitrile (3-APN) for constructing a pure 2D hybrid lead-iodide perovskite. The crystal structure of (3-APN)2PbI4 features a stable layered and undistorted PbI6 octahedral geometry (∠Pb-I-Pb = 180°) with a small I···I distance (4.66 Å), and the crystals grow in a dominant out-of-plane direction to the substrate. In addition, the existence of an intramolecular H bond between cyano groups and ammonium heads result in an appropriate valence band level of (3-APN)2PbI4 for a well-matched energy level alignment in the device, benefitting the interfacial charge transfer and hence a better photovoltaic performance. As a result, the PSC with the pure 2D (3-APN)2PbI4 perovskite-based PSC achieves a power conversion efficiency of 3.39%, which is the highest value thus far for the pure 2D lead-iodide perovskite family, to the best of our knowledge. More importantly, this pure 2D (3-APN)2PbI4 perovskite-based PSC demonstrates excellent stability against humidity. This work demonstrates that there is great potential to realize efficient and stable pure 2D perovskite-based PSCs through the wise design of organic cations.

Self-Assembled Ionic Liquid for Highly Efficient Electron Transport Layer-Free Perovskite Solar Cells.

Electron transport layer (ETL)-free perovskite solar cells (PSCs) are attractive because they have fewer layers and hence are lower in cost, but their inferior photovoltaic performance, as compared to ETL-containing PSCs, greatly restricts their practical application. This study concerns the design and synthesis of a hydroxyethyl-functionalized imidazolium iodide ionic liquid, the determination of its single crystal structure, and its self-assembly on a conductive substrate for ETL-free PSCs. The self-assembly of the ionic liquid on the conductive substrate is found to lower the work function of the conductive substrate and enhance interfacial electron extraction while retarding interfacial charge recombination. As a consequence, the power conversion efficiency is improved remarkably from 9.01 % to 17.31 % upon self-assembly of the ionic liquid on the conductive substrate. This finding provides a new way to assemble highly efficient ETL-free PSCs.

4-(Aminoethyl)pyridine as a Bifunctional Spacer Cation for Efficient and Stable 2D Ruddlesden-Popper Perovskite Solar Cells.

Two-dimensional (2D) Ruddlesden-Popper (RP) perovskites are attractive due to their appealing environmental stability. We demonstrate herein a spacer cation, 4-(aminoethyl)pyridine (4-AEP), for preparation of 2D RP perovskite films. The 4-AEP can not only act as a spacer cation but also coordinate with the Pb2+ ions in PbI2 with the nitrogen atom on the pyridine ring. High-quality 2D RP perovskite films can thus be formed as the coordination interaction retards the crystallization rate of the 2D RP perovskites. As a result, the solar cell employing the (4-AEP)2MAn-1PbnI3n+1 (n = 5) 2D perovskite achieves a power conversion efficiency (PCE) of 11.68% with good air stability, which is much better than the phenylethylamine spacer cation at the same conditions (PCE = 7.95%). This work provides a new idea for designing novel spacer cations toward efficient and stable 2D RP perovskite solar cells.

Pyridine-Terminated Conjugated Organic Molecules as an Interfacial Hole Transfer Bridge for NiOx-Based Perovskite Solar Cells.

To engineer the NiOx/perovskite interface and promote interfacial hole transfer, two pyridine-terminated conjugated small organic molecules (PTZ-1 and PTZ-2) are synthesized to link the NiOx and perovskite layers for NiOx-based perovskite solar cells (PSCs). One terminal pyridine group interacts with the NiOx layer, while the other one coordinates with the Pb atoms of the perovskite layer, erecting an interfacial hole transfer bridge between NiOx and perovskite. Surface modification of the NiOx film with the PTZ molecules is able to enhance hole extraction, increase hole mobility and conductivity of NiOx, reduce defect density, and retard interfacial charge recombination. As a consequence, power conversion efficiency is improved from 12.53 to 16.25 and 17.00% upon surface modifications of NiOx with PTZ-1 and PTZ-2, respectively. Furthermore, the modified PSCs exhibit almost no hysteresis and show good stability after storage in air (relative humidity of 30-40%) for 500 h without encapsulation.

Semi-synthesis and structural elucidation of brevicanines A-D, four new C19-diterpenoid alkaloids with rotameric phenomenon from Aconitum brevicalcaratum.

Four new C19-diterpenoid alkaloids brevicanines A-D (1-4) with rotameric phenomenon were isolated from Aconitum brevicalcaratum. They all possessed an unusual axial chiral phenyl-quinazoline side chain and their structures were elucidated by extensive spectroscopic analysis and chemical methods. Meanwhile, brevicanines A and B were semi-synthesized from their parent compound scaconine to further confirm their structures. Variable-temperature NMR spectroscopy was also used to investigate the atropisomers of brevicanine A, in which two sets of signals in 1H NMR spectra were observed at room temperature and coalesced over 140 °C. It's the first time to determine the atropisomeric preference of diterpenoid alkaloids.

Quaternary Iron Nickel Cobalt Selenide as an Efficient Electrocatalyst for Both Quasi-Solid-State Dye-Sensitized Solar Cells and Water Splitting.

Iron nickel cobalt selenides are synthesized through a one-step hydrothermal method. Quaternary Fe0.37 Ni0.17 Co0.36 Se demonstrates multifunctionality and shows high electrocatalytic activity for quasi-solid-state dye-sensitized solar cells with a power conversion efficiency of 8.42 %, the hydrogen evolution reaction, the oxygen evolution reaction, and water splitting. The electric power output from tandem quasi-solid-state dye-sensitized solar cells under one-sun illumination is sufficient to split water and exhibits a solar-to-hydrogen conversion efficiency of 5.58 % with Fe0.37 Ni0.17 Co0.36 Se as the electrocatalyst in this integrated system. Owing to a remarkable synergistic effect, quaternary Fe0.37 Ni0.17 Co0.36 Se is proven to be superior to ternary nickel cobalt selenide in terms of conductivity, electrocatalytic activity, and photovoltaic performance.

Development and Application of Genomic Resources in an Endangered Palaeoendemic Tree, Parrotia subaequalis (Hamamelidaceae) From Eastern China.

Parrotia subaequalis is an endangered palaeoendemic tree from disjunct montane sites in eastern China. Due to the lack of effective genomic resources, the genetic diversity and population structure of this endangered species are not clearly understood. In this study, we conducted paired-end shotgun sequencing (2 × 125 bp) of genomic DNA for two individuals of P. subaequalis on the Illumina HiSeq platform. Based on the resulting sequences, we have successfully assembled the complete chloroplast genome of P. subaequalis, as well as identified the polymorphic chloroplast microsatellites (cpSSRs), nuclear microsatellites (nSSRs) and mutational hotspots of chloroplast. Ten polymorphic cpSSR loci and 12 polymorphic nSSR loci were used to genotype 96 individuals of P. subaequalis from six populations to estimate genetic diversity and population structure. Our results revealed that P. subaequalis exhibited abundant genetic diversity (e.g., cpSSRs: Hcp = 0.862; nSSRs: HT = 0.559) and high genetic differentiation (e.g., cpSSRs: RST = 0.652; nSSRs: RST = 0.331), and characterized by a low pollen-to-seed migration ratio (r ≈ 1.78). These genetic patterns are attributable to its long evolutionary histories and low levels of contemporary inter-population gene flow by pollen and seed. In addition, lack of isolation-by-distance pattern and strong population genetic structuring in both marker systems, suggests that long-term isolation and/or habitat fragmentation as well as genetic drift may have also contributed to the geographic differentiation of P. subaequalis. Therefore, long-term habitat protection is the most important methods to prevent further loss of genetic variation and a decrease in effective population size. Furthermore, both cpSSRs and nSSRs revealed that P. subaequalis populations consisted of three genetic clusters, which should be considered as separated conservation units.

Metal Selenides as Efficient Counter Electrodes for Dye-Sensitized Solar Cells.

Solar energy is the most abundant renewable energy available to the earth and can meet the energy needs of humankind, but efficient conversion of solar energy to electricity is an urgent issue of scientific research. As the third-generation photovoltaic technology, dye-sensitized solar cells (DSSCs) have gained great attention since the landmark efficiency of ∼7% reported by O'Regan and Grätzel. The most attractive features of DSSCs include low cost, simple manufacturing processes, medium-purity materials, and theoretically high power conversion efficiencies. As one of the key materials in DSSCs, the counter electrode (CE) plays a crucial role in completing the electric circuit by catalyzing the reduction of the oxidized state to the reduced state for a redox couple (e.g., I3-/I-) in the electrolyte at the CE-electrolyte interface. To lower the cost caused by the typically used Pt CE, which restricts the large-scale application because of its low reserves and high price, great effort has been made to develop new CE materials alternative to Pt. A lot of Pt-free electrocatalysts, such as carbon materials, inorganic compounds, conductive polymers, and their composites with good electrocatalytic activity, have been applied as CEs in DSSCs in the past years. Metal selenides have been widely used as electrocatalysts for the oxygen reduction reaction and light-harvesting materials for solar cells. Our group first expanded their applications to the DSSC field by using in situ-grown Co0.85Se nanosheet and Ni0.85Se nanoparticle films as CEs. This finding has inspired extensive studies on developing new metal selenides in order to seek more efficient CE materials for low-cost DSSCs, and a lot of meaningful results have been achieved in the past years. In this Account, we summarize recent advances in binary and mutinary metal selenides applied as CEs in DSSCs. The synthetic methods for metal selenides with various morphologies and stoichiometric ratios and deposition methods for CE films are described. We emphasize that the in situ growth method exhibits advantages over other methods for fabricating stable and efficient CEs. We focus on the effect of morphology on the electocatalytic and photovoltaic performance. Application of transparent metal selenide CEs in bifacial DSSCs and the superiority of in situ-grown metal selenide nanosheet fiber CEs used for fiber DSSCs are presented. In addition, we show that metal selenides with a hollow sphere structure can function not only as an efficient electrocatalyst but also as a light-scattering layer. Finally, we present our views on the current challenges and future development of metal selenide CE materials.

Enhancing the Performance of Dye-Sensitized Solar Cells with a Gold-Nanoflowers Box.

To improve the electron collection, electron lifetime, and light-harvesting efficiency of dye-sensitized solar cells simultaneously, Au nanoflowers were prepared and used to cover the entire TiO2 film. Deposition of Au nanoflowers around the TiO2 film formed a light-scattering "box" that covered the entire TiO2 film. Compared with a light-scattering layer that only covers the top surface of TiO2 , the Au-nanoflowers box exhibited better light-harvesting efficiency due to omnidirectional light scattering, faster electron transport (attributed to the formation of electron channels between the metallic Au nanoflowers and the electron-collection electrode), and slower charge recombination. As a consequence, the short-circuit photocurrent and open-circuit photovoltage were both enhanced significantly, which improved the power conversion efficiency from 8.12 to 10.91 % (34 %) when an Au-nanoflowers box was wrapped around the photoanode.

Enhancing Perovskite Solar Cell Performance by Interface Engineering Using CH3NH3PbBr0.9I2.1 Quantum Dots.

To improve the interfacial charge transfer that is crucial to the performance of perovskite solar cells, the interface engineering in a device should be rationally designed. Here we have developed an interface engineering method to tune the photovoltaic performance of planar-heterojunction perovskite solar cells by incorporating MAPbBr3-xIx (MA = CH3NH3) quantum dots (QDs) between the MAPbI3 perovskite film and the hole-transporting material (HTM) layer. By adjustment of the Br:I ratio, the as-synthesized MAPbBr3-xIx QDs show tunable fluorescence and band edge positions. When the valence band (VB) edge of MAPbBr3-xIx QDs is located below that of the MAPbI3 perovskite, the hole transfer from the MAPbI3 perovskite film to the HTM layer is hindered, and hence, the power conversion efficiency decreases. In contrast, when the VB edge of MAPbBr3-xIx QDs is located between the VB edge of the MAPbI3 perovskite film and the highest occupied molecular orbital of the HTM layer, the hole transfer from the MAPbI3 perovskite film to the HTM layer is well-facilitated, resulting in significant improvements in the fill factor, short-circuit photocurrent, and power conversion efficiency.

Microsatellite markers for the critically endangered elm species Ulmus gaussenii (Ulmaceae).

The Anhui elm Ulmus gaussenii is listed as a critically endangered species by the International Union for Conservation of Nature and is endemic to China, where its only population is restricted to Langya Mountain in Chuzhou, Anhui Province. To better understand the population genetics of U. gaussenii, we developed 12 microsatellite markers using an improved technique. The 12 markers were polymorphic, with the number of alleles per locus ranging from two to nine. Observed and expected heterozygosities ranged from 0.021 to 0.750 and 0.225 to 0.744, respectively. The inbreeding coefficient ranged from -0.157 to 0.960. Significant linkage disequilibrium was detected for two pairs of loci, and significant deviations from Hardy-Weinberg equilibrium were found in nine loci. These microsatellite markers will contribute to the studies of population genetics in U. gaussenii, which in turn will contribute to species conservation and protection.

POSS-Based Electrolyte for Efficient Solid-State Dye-Sensitized Solar Cells at Sub-Zero Temperatures.

To expand the application of solid-state dye-sensitized solar cells (ssDSSCs) to low temperatures, it is necessary to develop new solid electrolytes with low glass transition temperature (Tg). The Tg is regulated by varying the length of alkyl chain that is connected with the nitrogen atom in the imidazolium ring linked to the polyhedral oligomeric silsesquioxane (POSS). The Tg as low as -8.8 °C is achieved with the POSS grafted with methyl-substituted imidazolium. The effect of alkyl group on the conductivity, Tg, and photovoltaic performance has also been investigated. The conductivity and power conversion efficiency increase with the alkyl length, while the Tg first increases and then decreases with the alkyl length. Among the synthesized POSS-based ionic conductors, the POSS grafted with the methyl-substituted imidazolium yields the highest power conversion efficiency of 6.98% at RT due to its highest conductivity, and the efficiency (6.52%) is still good at -4 °C, as its Tg (-8.8 °C) is lower than the working temperature (-4 °C). This finding suggests that the POSS-based solid electrolyte is promising for subzero-temperature applications of ssDSSCs.

Effect of the co-sensitization sequence on the performance of dye-sensitized solar cells with porphyrin and organic dyes.

To obtain a broad spectral response in the visible region, TiO2 film is co-sensitized with a porphyrin dye (FNE57 or FNE59) and an organic dye (FNE46). It is found that the stepwise co-sensitization in one single dye solution followed by in another single dye solution is better than the co-sensitization in a cocktail solution in terms of photovoltaic performance. The stepwise co-sensitization first with a porphyrin dye and then with an organic dye outperforms that in a reverse order. DSSC devices based on co-sensitizers FNE57 + FNE46 and FNE59 + FNE46 with a quasi-solid-state gel electrolyte generate power conversion efficiencies of 7.88% and 8.14%, respectively, which exhibits remarkable efficiency improvements of 61% and 35%, as compared with devices sensitized with the porphyrin dyes FNE57 and FNE59, respectively. Co-sensitization brings about a much improved short-circuit photocurrent due to the complementary absorption of the two sensitizers. The observed enhancement of incident monochromatic photon-to-electron conversion efficiency from individual dye sensitization to co-sensitization is attributed to the improved charge collection efficiency rather than to the light harvesting efficiency. Interestingly, the open-circuit photovoltage for the co-sensitization system comes between the higher voltage for the porphyrin dye (FNE57 or FNE59) and the lower voltage for the organic dye (FNE46), which is well correlated with their electron lifetimes. This finding indicates that not only the spectral complementation but also the electron lifetime should be considered to select dyes for co-sensitization.

Characterization of Perovskite Obtained from Two-Step Deposition on Mesoporous Titania.

The properties of perovskite films are sensitive to the fabrication method, which plays a crucial role in the performance of perovskite solar cell. In this work, we fabricate organo-lead iodide perovskite on mesoporous TiO2 films through two different two-step deposition methods, respectively, for the purpose of studying the crystal growth of perovskite film and its effect on light harvesting efficiency, defect density, charge extraction rate, and energy levels. The crystal growth exerts a significant influence on the morphology and hence the film properties, which are found to correlate with the performance of solar cells. It is found that vapor deposition of methylammonium iodide in the PbI2 lattice gives a more complete coverage on mesoporous TiO2 with a flatter surface and Fermi level closer to the middle of the band-gap, resulting in higher light absorption in the visible spectral region, lower defect density, and faster charge extraction, as compared to the sequential solution deposition. For this reason, the vapor-processed perovskite film achieves higher short-circuit photocurrent and power conversion efficiency than the solution-processed film.

Growth of Cu particles on a Cu2O truncated octahedron: tuning of the Cu content for efficient glucose sensing.

A simple and versatile hydrothermal method is developed to synthesize Cu-Cu2O, in which Cu particles grow on the surface of a Cu2O truncated octahedron. Through the reduction of Cu(2+) by glucose in an alkaline solution, the Cu2O truncated octahedron is quickly formed via a kinetic control process, and then Cu particles selectively nucleate on the high-energy (110) facets of Cu2O, generating a heterostructure. The amount of Cu in the sample is successfully tuned by varying the reaction temperature. Compared to Cu2O, the hybrid Cu-Cu2O architecture shows superior electrocatalytic performance for glucose oxidation due to the synergistic effect between more electrocatalytic active but less conductive Cu2O and more conductive but less electrocatalytic active Cu. By tuning the content of Cu in the heterostructure, the highest electrocatalytic activity is achieved at the Cu/Cu2O molar ratio of 0.83.

High-performance perovskite photoanode enabled by Ni passivation and catalysis.

Lead halide perovskites have achieved phenomenal successes in photovoltaics due to their suitable bandgaps, long diffusion lengths, and balanced charge transport. However, the extreme susceptibility of perovskites to water or air has imposed a seemingly insurmountable barrier for leveraging these unique materials into solar-to-fuel applications such as photoelectrochemical conversion. Here we developed a CH3NH3PbI3-based photoanode with an ultrathin Ni surface layer, which functions as both a physical passivation barrier and a hole-transferring catalyst. Remarkably, a much enhanced photocurrent density, an unassisted photoelectrochemical conversion capability, and a substantially better stability against water have been achieved, which are exceeding most of the previously reported photoanodes as well as a similar CH3NH3PbI3-based device structure but without the Ni surface layer. Our study suggests many exciting opportunities of developing perovskite-based solar-to-fuel conversion.