Electrochemistry and perovskite photovoltaics

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Special topic on organic and perovskite photovoltaics

<正>Photovoltaics, as a green technology for converting solar energy into electricity, have shown great promise to address the energy and environmental challenges for the sustainability of human society. In recent years, two types of photovoltaics, consisting of organic semiconductors or perovskites as light absorbers, have experienced a rapid development. The development of organic solar cells (OSC)can be dated back to 1986, since the discovery of a bilayer     

Stability of Sn-Pb mixed organic–inorganic halide perovskite solar cells:Progress,challenges,and perspectives

The exploration of low bandgap perovskite material to approach Shockley-Queisser limit of photovoltaic device is of great significance,but it is still challenging.During the past few years,tin–lead(Sn-Pb)mixed perovskites with low bandgaps have been rapidly developed,and their single junction solar cells have reached power conversion efficiency(PCE)over 21%,which also makes them ideal candidate as low bandgap sub-cell for tandem device.Nevertheless,due to the incorporation of unstable Sn²⁺,the stability issue becomes the vital problem for the further development of Sn-Pb mixed perovskite solar cells(PSCs).In this review,we are dedicated to give a full view in current understanding on the stability issue of SnPb mixed perovskites and their PSCs.We begin with the demonstration on the origin of instability of Sn-Pb mixed perovskites,including oxidation of Sn²⁺,defects,and interfacial layer induced instability.Sequentially,the up-to-date developments on the stability improvement of Sn-Pb mixed perovskites and their PSCs is systematically reviewed,including composition engineering,additive engineering,and interfacial engineering.At last,the current challenges and future perspectives on the stability study of Sn-Pb mixed PSCs are discussed,which we hope could promote the further application of Sn-Pb mixed perovskites towards commercialization.     

Current advancements on charge selective contact interfacial layers and electrodes in flexible hybrid perovskite photovoltaics

Perovskite-based photovoltaic materials have been attracting attention for their strikingly improved performance at converting sunlight into electricity.The beneficial and unique optoelectronic characteristics of perovskite structures enable researchers to achieve an incredibly remarkable power conversion efficiency.Flexible hybrid perovskite photovoltaics promise emerging applications in a myriad of optoelectronic and wearable/portable device applications owing to their inherent intriguing physicochemical and photophysical properties which enabled researchers to take forward advanced research in this growing field.Flexible perovskite photovoltaics have attracted significant attention owing to their fascinating material properties with combined merits of high efficiency,light-weight,flexibility,semitransparency,compatibility towards roll-to-roll printing,and large-area mass-scale production.Flexible perovskite-based solar cells comprise of 4 key components that include a flexible substrate,semi-transparent bottom contact electrode,perovskite(light absorber layer)and charge transport(electron/hole)layers and top(usually metal)electrode.Among these components,interfacial layers and contact electrodes play a pivotal role in influencing the overall photovoltaic performance.In this comprehensive review article,we focus on the current developments and latest progress achieved in perovskite photovoltaics concerning the charge selective transport layers/electrodes toward the fabrication of highly stable,efficient flexible devices.As a concluding remark,we briefly summarize the highlights of the review article and make recommendations for future outlook and investigation with perspectives on the perovskite-based optoelectronic functional devices that can be potentially utilized in smart wearable and portable devices.     

New small-molecular benzimidazole derivatives for photovoltaics: Synthesis,optical and electrochemical properties and application in perovskite solar cells

New small molecule photovoltaic materials containing benzimidazole fragment were prepared by cross-coupling of the corresponding 1-bromo-4-(imidazol-2-yl)benzenes with multiborylated/stannylated polycyclic (het)arenes. Energies of HOMO/LUMO levels were calculated from cyclic voltammetry and UV/VIS spectroscopy data and are within the ranges –5.27... –5.73 and –2.33...–2.89 eV, respectively. Solar cells based on three different perovskites as light absorbing layers and compound SM7 as electron transporting material demonstrated power conversion efficiency values up to 10.78% without doping additives or perovskite engineering.     

钙钛矿型复合氧化物光催化研究进展

扼要叙述了钙钛矿型复合氧化物(ABO3)作为光催化剂的研究进展。包括结构,机理,制备,改性和研究现状。强调了结构与性能之间的关系并对其研究方向提出了自己的见解。     

Modification and application of 1,2,5-oxadiazolo[3,4-b]pyrazine derivatives: highlights and perspectives

Russian Chemical Bulletin - The review summarized and classified the data on the construction of [1,2,5]oxadiazolo[3,4-b]pyrazine scaffold and its further modifications published over the past 20...     

Stability,encapsulation and large-area fabrication of organic photovoltaics

Organic photovoltaics(OPVs) have become a timely research topic for their advantages of light weight, low cost, low toxicity,environmental adaptability, flexibility, and large-area manufacture, especially after non-fullerene acceptor ITIC reported in 2015.The highest power conversion efficiency(PCE) is currently above 18% for OPV. However, there are still imparities in the efficiency of OPVs when compared with silicon-based photovoltaics, as well as in their shelf life. Compared with inorganicbased photovoltaics, the efficiency of large-area OPVs is lower and the life time of OPVs is shorter. Therefore, such inferior performance of large-area OPVs restricts the commercial development. Based on these constraints, this paper reviews the research work regarding OPVs into three aspects: stability, encapsulation technology, and recent large-area preparation technologies.     

Halogen in materials design: Chloroammonium lead triiodide perovskite (ClNH3PbI3) a dynamical bandgap semiconductor in 3D for photovoltaics

Methylammonium lead trihalides and their derivatives are photovoltaic materials. CH₃NH₃PbI₃ is the most efficient light harvester among all the known halide perovskites (PSCs). It is regarded as unsuitable for long‐term stable solar cells, thus it is necessary to develop other types of PSC materials to achieve stable PSCs (Wang et al., Nat. Energy 2016, 2, 16195). Because of this, various research efforts are on‐going to discover novel lead‐based or lead‐free single/double PSCs, which can be stable, synthesizable, transportable, abundant and efficient in solar energy conversion. Keeping these factors in mind, we report here the electronic structures, energetic stabilities and some materials properties (viz. band structures, density of states spectra and photo‐carrier masses) of the PSC chloroammonium lead triiodide (ClNH₃PbI₃). This emerges through compositional engineering that often focuses on B‐ and Y‐site substitutions within the domain of the BMY₃ PSC stoichiometry. ClNH₃PbI₃ is found to be stable as orthorhombic and pseudocubic polymorphs, which are analogous with the low and high temperature polymorphs of CH₃NH₃PbI₃. The bandgap of ClNH₃PbI₃ (values between 1.28 and 1.60 eV) is found to be comparable with that of CH₃NH₃PbI₃, (1.58 eV), both obtained with periodic DFT at the PBE level of theory. Spin orbit coupling is shown to have a pronounced effect on both the magnitude and character of the bandgap. The computed results show that ClNH₃PbI₃ may act as a competitor for CH₃NH₃PbI₃ for photovoltaics. © 2018 Wiley Periodicals, Inc.     

Synthesis of dispersed metal particles for applications in photovoltaics, catalysis, and electronics

In colloid and nanoparticle chemistry, particle size, shape, crystallinity, surface morphology, and composition are controlled by employing the mechanisms of burst nucleation, diffusional growth, aggregation, or their combinations. Here we review and survey practical examples of recently developed methods for preparing metal colloids and nanoparticles for industrial applications such as photovoltaics, catalysis, and consumer electronics. We discuss relevant theoretical models, many of which are general, and identify growth mechanisms that play a major role in other systems and applications as well.     

MXene fibers for electronic textiles: Progress and perspectives

The rapid evolution of portable and wearable electronic devices has fueled the development of smart functional textiles that are able to conduct electricity, sense body movements, or store energy. One main challenge inhibiting the further development of functional textile-based electronics is the lack of robust functional fibers with suitable electrical, electrochemical and sensing functionalities. MXenes, an emerging family of two-dimensional(2D) materials, have shown to be promising candidates...     

Au/NiO 催化剂的XRD、TEM、TPR及XPS表征研究

采用XRD、TEM、TPR及XPS等表征手段，对共沉淀法制备的Au/NiO催化剂的活性中心，载体的结构及状态进行了研究。结果表明，活性中心金以纳米尺寸高度分散于载体表面，部分金可能呈现氧化状态，载体结晶适度。     

Thermodynamics of solid solution formation in NiOMgO and NiOZnO

High-temperature calorimetric measurements of the enthalpies of solution in molten 2PbO · B₂O₃ of (Ni_xMg_1?x)O and (Ni_xZn_1?x)O permit the calculation of the enthalpy of the zincite to rocksalt transformation in ZnO, and the enthalpies of mixing, relative to rocksalt standard states, in the two solid solution series. The enthalpy of the zincite to rocksalt transformation is 24,488 ± 3,592 J mole^?1 with a corresponding positive entropy change of 0.48 ± 3.3 J K^?1 mole^?1. The small positive entropy change for the transformation necessitates a very flat and perhaps negative $\text{dP}\text{dT}$ slope for the phase boundary. Both solid solutions, when referred to rocksalt standard states, show negative enthalpies of mixing. For (Ni_xMg_1?x)O the negative enthalpies of mixing are fitted by a subregular model, where ΔH_mix = X_AX_B(BX_A + AX_B), with A = ?21,971 ± 4,953 J mole^?1 and B = ?5103 ± 1151 J mole^?1. The associated negative excess entropies of mixing, calculated from the heats of mixing and previously measured activity-composition relations, are similarly modeled with A = ?10.7 J K^?1 mole^?1 and B = + 1.1 J K^?1 mole^?1. Negative enthalpies of mixing in (Ni_xZn_1?x)O conform to a regular solution model with W = ?13520 ± 5581 J mole^?1. The negative enthalpies of mixing are interpreted in terms of a tendency toward ordering in the solid solutions, the proposed ordering scheme finding support in spectroscopic, structural, and magnetic data. These tendencies toward order are used to explain observed phase relations and thermodynamic properties in some other systems containing a transition metal cation and another ion of similar size, namely carbonates, hydrated sulfates and the systems CuOMO (M = Mg, Co, Ni).     

Horror, happenings and highlights in the history of vacuum physics

The origin of vacuum physics can be traced back to a statement of Aristotle that a vacuum cannot exist, which was questioned by Otto von Guericke. He tried to answer the question by experiment and was one of the most successful personalities to overcome medieval thought, and to pave the way to a new vistas for science and technology. His life and his famous demonstrations are described and a short account of the development of his apparatus and the impact on research in various countries is discussed. A list of old and newer reviews concludes the article.     

Van der Waals effects on structure and optical properties in organic photovoltaics

We have recently reported that dispersion forces can have drastic effects on the structure and charge separation in organic photovoltaics (OPVs) (Martinez et al., J. Phys. Chem. C 121, 20 134 [2017]). Here we investigate dimer complexes formed by the polymer P3HT and the fullerene derivative PCBM. We show how van der Waals (vdW) interactions affect the geometrical structure, which has strong effects on the electronic structure and UV-Vis absorption spectrum. Time-dependent density functional theory calculations demonstrate that the experimentally observed blue-shift of the absorption maximum of P3HT/PCBM OPV cells with respect to pure P3HT results mainly from distortions in P3HT due to vdW interactions between donor and acceptor fragments. Reduced absorption in the red region of the UV-Vis spectrum results from distortions of P3HT and small charge transfer between P3HT and PCBM. These results are in qualitative agreement with experiments and recent theoretical results on the corresponding solid-state films.     

Design, synthesis, and characterization of novel nanowire structures for photovoltaics and intracellular probes

Semiconductor nanowires (NWs) represent a unique system for exploring phenomena at the nanoscale and are expected to play a critical role in future electronic, optoelectronic, and miniaturized biomedical devices. Modulation of the composition and geometry of nanostructures during growth could encode information or function, and realize novel applications beyond the conventional lithographical limits. This review focuses on the fundamental science aspects of the bottom-up paradigm, which are synthesis and physical property characterization of semiconductor NWs and NW heterostructures, as well as proof-of-concept device concept demonstrations, including solar energy conversion and intracellular probes. A new NW materials synthesis is discussed and, in particular, a new "nanotectonic" approach is introduced that provides iterative control over the NW nucleation and growth for constructing 2D kinked NW superstructures. The use of radial and axial p-type/intrinsic/n-type (p-i-n) silicon NW (Si-NW) building blocks for solar cells and nanoscale power source applications is then discussed. The critical benefits of such structures and recent results are described and critically analyzed, together with some of the diverse challenges and opportunities in the near future. Finally, results are presented on several new directions, which have recently been exploited in interfacing biological systems with NW devices.