二极管特性简化模型在染料敏化太阳能电池电流-电压曲线拟合及在光电特性参数评估中的应用

利用瞬态光电导技术研究了在一个大的偏压范围内染料敏化太阳能电池(DSSC)中的电荷收集和电荷复合过程的动力学. 结果表明, 在不同的电压下电荷收集速率远快于电荷复合速率, 用以解释电荷的收集效率几乎不变. 基于这个结果, 简化了DSSC二极管特性模型, 从而实现了对电流-电压(I-V)曲线的直接拟合. 利用这一模型拟合的结果提取出一系列与工作条件下DSSC光电转化过程相关的参数, 可以用以描述包括电荷生成、电荷收集和复合以及DSSC器件的整流特性等关键性质. 将这一拟合方法应用于不同叔丁基吡啶(TBP)浓度电解液的电池, 获得的结果表明, 不同TBP浓度可以导致电荷复合速率有较大的差别, 但对电荷的收集速率影响甚小, 这与I-V曲线拟合的结果非常吻合. 同时研究证明TBP浓度对电池的理想因子(m)的影响较为明显,即高浓度TBP的DSSC对应大的m值以及较慢的电荷复合速率.     

Optimization of electrospun TiO2 nanofibers photoanode film for dye‐sensitized solar cells through interfacial pre‐treatment,controllable calcination,and surface post‐treatment

Dye‐sensitized solar cells (DSSCs) are generally viewed as next generation photovoltaic devices. Electrospun TiO₂ nanofibers (NFs) film can be used to construct photoanode for DSSCs. A systematic strategy to optimize such a novel photoanode material of DSSCs was elaborated in this paper. A main drawback of NFs photoanode is the poor adhesion of ceramic NFs film to its conductive glass substrate. This problem can be well solved by sandwiching a transition layer between the overlaid NFs film and the underlaid glass substrate through an interfacial spin‐coating pre‐treatment. After electrospinning, a controllable calcination is also indispensable for obtaining an ideal nanofibrous mat with good morphology and adhesion. The choice of calcination parameters including temperature, holding time, and heating rate was discussed in detail. In addition, a surface TiCl₄ post‐treatment can further improve adhesion as well as strength for the NFs photoanode film. And the performance of the resulting DSSCs will benefit from the TiCl₄ post‐treatment. Copyright © 2013 John Wiley & Sons, Ltd.     

Perspectives on ab initio molecular simulation of excited-state properties of organic dye molecules in dye-sensitised solar cells

In this mini-review, we summarise and critique the emerging field of quantum-based molecular simulation of dye-sensitised solar cells (DSSCs), with particular focus on the deployment of organic-based dyes therein. We assess the underlying methodologies, including developments, pitfalls and challenges, whilst gauging predictive performance vis-à-vis experimental performance. The predictive capabilities of simulation methods with respect to elucidation of underlying methods is considered in the light of progress towards the ultimate goal of predictive in silico design of DSSCs, to complement hand-in-hand experimental approaches in the development of state-of-the-art DSSC devices.     

Wet-process preparation of nickel-based photoanode for TCO-less fiber-shaped dye-sensitized solar cells

Low-cost ZnO-type fiber-shaped dye-sensitized solar cells (DSSC) without transparent conductive oxide (TCO) were for the first time assembled through a low-temperature all-wet process, using a series of Ni-based composite fiber. Both Ni layer morphology and ZnO nano-array structure evidently influenced the performance of the corresponding DSSC. For applications in both liquid type and all-solid CuI type fiber-shaped DSSCs, the Ni-based photoanode is comparable with the Ti- or Fe-based photoanode. Our all-solid CuI type fiber-shaped DSSCs was even better than that of the reported all-solid Ti- or Fe-based devices with the same oxide thickness. Electrochemical analysis further indicated that side reactions on the electrode/electrolyte interface could be effectively suppressed after a layer of Ni plated. Even for Cu wire, of which its interfacial side reactions are too complicated for application in DSSC, the Cu/Ni composite fiber still works well. Similar technology can be used to fabricate many other low-cost and light-weight conductive fibers, which are potential photoanode materials for highly efficient TCO-less DSSCs.     

The evolution of organic materials for efficient dye-sensitized solar cells

In the past three decades, dye-sensitized solar cells (DSSCs) have gained increased recognition as a potential substitute for inexpensive photovoltaic (PV) devices, and their maximum efficiency has grown from 7% to 14.3%. Recent developments in DSSCs have attracted a plethora of research activities geared at realizing their full potential. DSSCs have seen a revival as the finest technology for specific applications with unique features such as low-cost, non-toxic, colourful, transparent, ease of fabrication, flexibility, and efficient indoor light operation. Several organic materials are being explored and employed in DSSCs to enhance their performance, robustness, and lower production costs to be viable alternatives in the solar cell markets. This review provides a concise summary of the developments in the field over the past decade, with a special focus on the incorporation of organic materials into DSSCs. It covers all elements of the DSSC technology, including practical approaches and novel materials. Finally, the emerging applications of DSSCs, and their future promise are also discussed.     

Photophysical and Electrochemical Properties,and Molecular Structures of Organic Dyes for Dye‐Sensitized Solar Cells

Dye‐sensitized solar cells (DSSCs) based on organic dyes adsorbed on oxide semiconductor electrodes, such as TiO₂, ZnO, or NiO, which have emerged as a new generation of sustainable photovoltaic devices, have attracted much attention from chemists, physicists, and engineers because of enormous scientific interest in not only their construction and operational principles, but also in their high incident‐solar‐light‐to‐electricity conversion efficiency and low cost of production. To develop high‐performance DSSCs, it is important to create efficient organic dye sensitizers, which should be optimized for the photophysical and electrochemical properties of the dyes themselves, with molecular structures that provide good light‐harvesting features, good electron communication between the dye and semiconductor electrode and between the dye and electrolyte, and to control the molecular orientation and arrangement of the dyes on a semiconductor surface. The aim of this Review is not to make a list of a number of organic dye sensitizers developed so far, but to provide a new direction in the epoch‐making molecular design of organic dyes for high photovoltaic performance and long‐term stability of DSSCs, based on the accumulated knowledge of their photophysical and electrochemical properties, and molecular structures of the organic dye sensitizers developed so far.     

Recent Advances on Pt-Free Electro-Catalysts for Dye-Sensitized Solar Cells

Since Prof. Grätzel and co-workers achieved breakthrough progress on dye-sensitized solar cells (DSSCs) in 1991, DSSCs have been extensively investigated and wildly developed as a potential renewable power source in the last two decades due to their low cost, low energy-intensive processing, and high roll-to-roll compatibility. During this period, the highest efficiency recorded for DSSC under ideal solar light (AM 1.5G, 100 mW cm⁻²) has increased from ~7% to ~14.3%. For the practical use of solar cells, the performance of photovoltaic devices in several conditions with weak light irradiation (e.g., indoor) or various light incident angles are also an important item. Accordingly, DSSCs exhibit high competitiveness in solar cell markets because their performances are less affected by the light intensity and are less sensitive to the light incident angle. However, the most used catalyst in the counter electrode (CE) of a typical DSSC is platinum (Pt), which is an expensive noble metal and is rare on earth. To further reduce the cost of the fabrication of DSSCs on the industrial scale, it is better to develop Pt-free electro-catalysts for the CEs of DSSCs, such as transition metallic compounds, conducting polymers, carbonaceous materials, and their composites. In this article, we will provide a short review on the Pt-free electro-catalyst CEs of DSSCs with superior cell compared to Pt CEs; additionally, those selected reports were published within the past 5 years.     

A fast approach to optimize dye loading of photoanode via ultrasonic technique for highly efficient dye-sensitized solar cells

A distinctive method is proposed by simply utilizing ultrasonic technique in TiO_2 electrode fabrication in order to improve the optoelectronic performance of dye-sensitized solar cells(DSSCs). Dye molecules are at random and single molecular state in the ultrasonic field and the ultrasonic wave favors the diffusion and adsorption processes of dye molecules. As a result, the introduction of ultrasonic technique at room temperature leads to faster and more well-distributed dye adsorption on TiO_2 as well as higher cell efficiency than regular deposition, thus the fabrication time is markedly reduced. It is found that the device based on40 kHz ultrasonic(within 1 h) with N719 exhibits a Vocof 789 mV, Jscof 14.94 mA/cm~2 and fill factor(FF)of 69.3, yielding power conversion efficiency(PCE) of 8.16%, which is higher than device regularly dyed for12 h(PCE = 8.06%). In addition, the DSSC devices obtain the best efficiency(PCE = 8.68%) when the ultrasonic deposition time increases to 2.5 h. The DSSCs fabricated via ultrasonic technique presents more dye loading,larger photocurrent, less charge recombination and higher photovoltage. The charge extraction and electron impedance spectroscopy(EIS) were performed to understand the influence of ultrasonic technique on the electron recombination and performance of DSSCs.     

Bio-inspired multi-scale structures in dye-sensitized solar cell

Dye-sensitized solar cells (DSSCs) provide a technique and economic alternative concept to present p–n junction photovoltaic devices. For a DSSC, light is absorbed by a sensitizer, which is anchored to the surface of a wide band semiconductor. Charge separation takes place at the interface via photo-induced electron injection from the dye into the conduction band of the semiconductor. Nanocrystalline oxide semiconductor photo-anode films play an important role in photo-electrical conversion efficiency of DSSCs. In this review, we summarize the recent advances of multi-scale structures of DSSCs in the view of bio-inspired materials and analyze the influence factors of a variety of multi-scale structures on photo-electrical conversion in DSSCs, which will provide a strategy for structure design on the novel solar cell.     

Kinetics of electron recombination of dye-sensitized solar cells based on TiO2 nanorod arrays sensitized with different dyes

The performance and electron recombination kinetics of dye-sensitized solar cells based on TiO(2) films consisting of one-dimensional nanorod arrays (NR-DSSCs) which are sensitized with dyes N719, C218 and D205, respectively, have been studied. It has been found that the best efficiency is obtained with the dye C218 based NR-DSSCs, benefiting from a 40% higher short-circuit photocurrent density. However, the open circuit photovoltage of the N719 based cell is 40 mV higher than that of the organic dye C218 and D205 based devices. Investigation of the electron recombination kinetics of the NR-DSSCs has revealed that the effective electron lifetime, τ(n), of the different dye based NR-DSSCs shows the sequence of C218 > D205 > N719. The higher V(oc) with the N719 based NR-DSSC is originated from the more negative energy level of the conduction band of the TiO(2) film. In addition, in comparison to the DSSCs with the conventional nanocrystalline particles based TiO(2) films, the NR-DSSCs have shown over two orders of magnitude higher τ(n) when employing N719 as the sensitizer. Nevertheless, the τ(n) of the DSSCs with the C218 based nanorod arrays is only ten-fold higher than that of the nanoparticles based devices. The remarkable characteristic of the dye C218 in suppressing the electron recombination of DSSCs is discussed.     

Near Infrared Organic Semiconducting Materials for Bulk Heterojunction and Dye‐Sensitized Solar Cells

Dye sensitized solar cells (DSSCs) and bulk heterojunction (BHJ) solar cells have been the subject of intensive academic interest over the past two decades, and significant commercial effort has been directed towards this area with the vison of developing the next generation of low cost solar cells. Materials development has played a vital role in the dramatic improvement of both DSSC and BHJ solar cell performance in the recent years. Organic conjugated polymers and small molecules that absorb solar light in the visible and near infrared (NIR) regions represent a class of emering materials and show a great potential for the use of different optoelectronic devices such as DSSCs and BHJ solar cells. This account describes the emering class of near infrared (NIR) organic polymers and small molecules having donor and acceptors units, and explores their potential applications in the DSSCs and BHJ solar cells.     

Facile synthesis of TiO2 inverse opal electrodes for dye-sensitized solar cells

Engineering of TiO(2) electrode layers is critical to guaranteeing the photoconversion efficiency of dye-sensitized solar cells (DSSCs). Recently, a novel approach has been introduced for producing TiO(2) electrodes using the inverted structures of colloidal crystals. This paper describes a facile route to producing ordered macroporous electrodes from colloidal crystal templates for DSSCs. Using concentrated colloids dispersed in a volatile medium, the colloidal crystal templates were obtained within a few minutes, and the thickness of the template was easily controlled by changing the quantity of colloidal solution deposited. Here, the effects of the structural properties of the inverse opal TiO(2) electrodes on the photovoltaic parameters of DSSCs were investigated. The photovoltaic parameters were measured as a function of pore ordering and electrode film thickness. Moreover, DSSC applications that used either liquid or viscous polymer electrolyte solutions were investigated to reveal the effects of pore size on performance of an inverse opal TiO(2) electrode.     

Osmium Polypyridyl Complexes and Their Applications to Dye‐Sensitized Solar Cells

Dye‐sensitized solar cells (DSSCs) have received much attention in recent years owing to their efficient conversion of sunlight to electricity. DSSCs became successful alternatives to silicon photovoltaic devices by virtue of their low fabrication costs and easy preparation methods. In DSSCs the dye plays the key role. This review summarizes the applications of osmium sensitizers in DSSCs. We also briefly discussed their synthesis and the effect of various electrolyte systems on device efficiencies.     

Exploration on Charge Transfer and Absorption Spectra of Spiro[fluorene-9,90-xanthene]-based Polyoxometalate Hybrids Toward High Performance Dye-sensitized Solar Cell

Based on spiro[fluorene-9,90-xanthene](SFX, dye 1), the Lindqvist-type polyoxometalate(POM) functionalized with SFX and its derivatives(dyes 2-4) used in dye-sensitized solar cells(DSSCs) were designed and investigated with the density functional theory(DFT) and time-dependent DFT(TD-DFT) calculations. The results indicate that Lindqvist-type POM is the main contribution to the lowest unoccupied molecular orbital(LUMO) and affects the LUMO energies of dyes 2-4. The maximum absorptions of the designed dyes containing POM(dyes 2-4) are red shifted comparing with that of dye 1. The introduction of electron-donating group onto SFX segment is helpful to red shift the absorption spectra. The major factors affecting the performance of DSSCs, including light harvesting and electron injection were evaluated. Considering the absorption spectra and photovoltaic parameters, dyes 3 and 4 are promising high performance dye sensitizers in n-type DSSCs.     

New architectures for dye-sensitized solar cells

Modern dye-sensitized solar cell (DSSC) technology was built upon nanoparticle wide bandgap semiconductor photoanodes. While versatile and robust, the sintered nanoparticle architecture exhibits exceedingly slow electron transport that ultimately restricts the diversity of feasible redox mediators. The small collection of suitable mediators limits both our understanding of an intriguing heterogeneous system and the performance of these promising devices. Recently, a number of pseudo-1D photoanodes that exhibit accelerated charge transport and greater materials flexibility were fabricated. The potential of these alternative photoanode architectures for advancing, both directly and indirectly, the performance of DSSCs is explored.     

Combining Electron‐Accepting Phthalocyanines and Nanorod‐like CuO Electrodes for p‐Type Dye‐Sensitized Solar Cells

A route is reported for the synthesis of two electron‐accepting phthalocyanines featuring linkers with different lengths as sensitizers for p‐type dye‐sensitized solar cells (DSSCs). Importantly, our devices based on novel nanorod‐like CuO photocathodes showed high efficiencies of up to 0.191 %: the highest value reported to date for CuO‐based DSSCs.     

Development on Solid Polymer Electrolytes for Electrochemical Devices

Electrochemical devices, especially energy storage, have been around for many decades. Liquid electrolytes (LEs), which are known for their volatility and flammability, are mostly used in the fabrication of the devices. Dye-sensitized solar cells (DSSCs) and quantum dot sensitized solar cells (QDSSCs) are also using electrochemical reaction to operate. Following the demand for green and safer energy sources to replace fossil energy, this has raised the research interest in solid-state electrochemical devices. Solid polymer electrolytes (SPEs) are among the candidates to replace the LEs. Hence, understanding the mechanism of ions’ transport in SPEs is crucial to achieve similar, if not better, performance to that of LEs. In this paper, the development of SPE from basic construction to electrolyte optimization, which includes polymer blending and adding various types of additives, such as plasticizers and fillers, is discussed.     

High-Performance Dipolar Organic Dyes with an Electron-Deficient Diphenylquinoxaline Moiety in the π-Conjugation Framework for Dye-Sensitized Solar Cells

We report here the synthesis and electrochemical and photophysical properties of a series of easily prepared dipolar organic dyes and their application in dye-sensitized solar cells (DSSCs). For the six organic dyes, the molecular structures comprised a triphenylamine group as an electron donor, a cyanoacrylic acid as an electron acceptor, and an electron-deficient diphenylquinoxaline moiety integrated in the π-conjugated spacer between the electron donor and acceptor moieties. The incorporation of the electron-deficient diphenylquinoxaline moiety effectively reduces the energy gap of the dyes and broadly extends the spectral coverage. DSSCs based on dye 6 produced the best overall cell performance of 7.35?%, which translates to approximately 79?% of the intrinsic efficiency of the DSSCs based on the standard N719 dye under identical experimental conditions. The high performance of DSSCs based on dye 6 among the six dyes explored is attributed to the combined effects of high dye loading on a TiO(2) surface, rapid dye regeneration, and effective retardation of charge recombination.     

Supramolecular Hemicage Cobalt Mediators for Dye‐Sensitized Solar Cells

A new class of dye‐sensitized solar cells (DSSCs) using the hemicage cobalt‐based mediator [Co(ttb)]^2+/3+ with the highly preorganized hexadentate ligand 5,5′′,5′′′′‐((2,4,6‐triethyl benzene‐1,3,5‐triyl)tris(ethane‐2,1‐diyl))tri‐2,2′‐bipyridine (ttb) has been fully investigated. The performances of DSSCs sensitized with organic D –π–A dyes utilizing either [Co(ttb)]^2+/3+ or the conventional [Co(bpy)₃]^2+/3+ (bpy=2,2′‐bipyridine) redox mediator are comparable under 1000 W m^?2 AM 1.5 G illumination. However, the hemicage complexes exhibit exceptional stability under thermal and light stress. In particular, a 120‐hour continuous light illumination stability test for DSSCs using [Co(ttb)]^2+/3+ resulted in a 10 % increase in the performance, whereas a 40 % decrease in performance was found for [Co(bpy)₃]^2+/3+ electrolyte‐based DSSCs under the same conditions. These results demonstrate the great promise of [Co(ttb)]^2+/3+ complexes as redox mediators for efficient, cost‐effective, large‐scale DSSC devices.     

Effect of Different π-Conjugated Dyes Containing 4,5-Diazafluorenone-9- Hydrazone on The Performance of Dye-Sensitized Solar Cells

In this study, two ligands and their ruthenium complexes are synthesized and their photovoltaic properties for dye-sensitized solar cells (DSSCs) of new substances substituted by 4,5-diazafluorenone-9-hydrazone groups is investigated. The structures of the compounds are determined by FTIR, UV-Vis, HNMR, CNMR, and MS spectroscopic techniques. The photovoltaic and electrochemical properties of these compounds are investigated and the applicability in DSSCs as photo sensitizers is studied. Photovoltaic cell efficiencies (PCEs) of the devices are in the range 0.08-1.54% under simulated AM 1.5 solar irradiation of 100 mW/cm², and the highest open-circuit voltage (V_oc) reaches 0.43 V. When the photovoltaic performance of the DSSC devices is compared, it indicates that PCEs assume the following: P1–Ru > > P2–Ru > P1 > P2. The PCE value of 1.54% is obtained with DSSC based on P1–Ru under AM irradiation (100 mW/cm²). DSSC based on the P1–Ru produced efficiency of 1.54% whereas DSSC-based P1 exhibits the device performance with an efficiency of 0.08% under illumination. These results suggest that a larger π-conjugated bridge and a richer electron donor of P1–Ru are beneficial for the photovoltaic performance of DSSC.