染料共敏化纳米晶太阳能电池的性能研究

采用罗丹明-B与香豆素混合的方法,配制成敏化剂修饰纳米晶薄膜.实验结果证明,这种共敏化的方法可以在可见光范围内有效提高电池的吸光度,使得电池的性能比单独使用罗丹明-B敏化有了大幅度提高.实验中,罗丹明-B与香豆素共敏化的电池的开路电压达到了550mV,短路电流达到了0.1375mA/cm^2.     

A Near‐Infrared cis‐Configured Squaraine Co‐Sensitizer for High‐Efficiency Dye‐Sensitized Solar Cells

A cis‐configured squaraine dye (HSQ1), synthesized by incorporation of a strongly electron‐withdrawing dicyanovinyl group into the central squaric acid moiety, is employed in dye‐sensitized solar cells (DSCs). In solution, HSQ1 displays an intense absorption in the near‐infrared region with a maximum at 686 nm and when the dye is adsorbed on a TiO₂ surface, the absorption spectrum broadens in both the blue and the near‐infrared regions, which is favorable for efficient light harvesting over a broad wavelength range. A solar cell sensitized with HSQ1 shows a broader incident photon‐to‐current conversion efficiency (IPCE) spectrum (from 400 to 800 nm) and a higher IPCE in the long‐wavelength region (71% at 700 nm) than a cell sensitized with squaraine dye SQ1. Furthermore, a solar cell co‐sensitized with HSQ1 and N3 dye shows remarkably improved short‐circuit current density and open‐circuit voltage compared to those of a DSC based on N3 alone and fabricated under the same conditions. The energy‐conversion efficiency of the co‐sensitized DSC is 8.14%, which is the highest reported efficiency for a squaraine dye–based co‐sensitized DSC without using Al₂O₃ layer.     

Transparent conductive oxide‐less three‐dimensional cylindrical dye‐sensitized solar cell fabricated with flexible metal mesh electrode

A cylindrical transparent conductive oxide‐less dye‐sensitized solar cell (DSSC) consisting of glass tube/stainless steel mesh–TiO₂–dye/gel electrolytes/Pt‐Ti rod having capability of self‐light trapping is reported. Replacing the glass tube with heat‐shrinkable tube to reduce electrolyte gap and optical loss due to light transmission and reflection led to the enhancement in the power conversion efficiency from 2.61% to 3.91%. Profiling of the current distribution measured by laser beam‐induced current exhibited nearly the same current in the axial and radial directions, suggesting that light reflection on a cylindrical DSSC does not affect the efficiency seriously. Optimized best DSSC in this novel device architecture gave a short‐circuit current density of 11.94 mA/cm², an open‐circuit voltage of 0.71 V and a fill factor of 0.66 leading to the power conversion efficiency of 5.58% at AM 1.5 under simulated solar irradiation. Copyright © 2011 John Wiley & Sons, Ltd.     

Estimating the Maximum Attainable Efficiency in Dye‐Sensitized Solar Cells

For an ideal solar cell, a maximum solar‐to‐electrical power conversion efficiency of just over 30% is achievable by harvesting UV to near IR photons up to 1.1 eV. Dye‐sensitized solar cells (DSCs) are, however, not ideal. Here, the electrical and optical losses in the dye‐sensitized system are reviewed, and the main losses in potential from the conversion of an absorbed photon at the optical bandgap of the sensitizer to the open‐circuit voltage generated by the solar cell are specifically highlighted. In the first instance, the maximum power conversion efficiency attainable as a function of optical bandgap of the sensitizer and the “loss‐in‐potential” from the optical bandgap to the open‐circuit voltage is estimated. For the best performing DSCs with current technology, the loss‐in‐potential is ～0.75 eV, which leads to a maximum power‐conversion efficiency of 13.4% with an optical bandgap of 1.48 eV (840 nm absorption onset). Means by which the loss‐in‐potential could be reduced to 0.4 eV are discussed; a maximum efficiency of 20.25% with an optical bandgap of 1.31 eV (940 nm) is possible if this is achieved.     

Surface Design in Solid‐State Dye Sensitized Solar Cells: Effects of Zwitterionic Co‐adsorbents on Photovoltaic Performance

In solid‐state dye sensitized solar cells (SSDSCs) charge recombination at the dye‐hole transporting material interface plays a critical role in the cell efficiency. For the first time we report on the influence of dipolar co‐adsorbents on the photovoltaic performance of sensitized hetero‐junction solar cells. In the present study, we investigated the effect of two zwitterionic butyric acid derivatives differing only in the polar moiety attached to their common 4 carbon‐chain acid, i.e., 4‐guanidinobutyric acid (GBA) and 4‐aminobutyric acid (ABA). These two molecules were implemented as co‐adsorbents in conjunction with Z907Na dye on the SSDSC. It was found that a Z907Na/GBA dye/co‐adsorbent combination increases both the open circuit voltage (V_oc) and short‐circuit current density (J_sc) as compared to using Z907Na dye alone. The Z907Na/ABA dye/co‐adsorbent combination increases the J_sc. Impedance and transient photovoltage investigations elucidate the cause of these remarkable observations.     

Band‐Edge Engineered Hybrid Structures for Dye‐Sensitized Solar Cells Based on SnO2 Nanowires

In this report, we show for the first time that SnO₂ nanowire based dye sensitized solar cells exhibit an open circuit voltage of 560 mV, which is 200 mV higher than that using SnO₂ nanoparticle based cells. This is attributed to the more negative flat band potential of nanowires compared to the nanoparticles as determined by open circuit photo voltage measurements made at high light intensities. The nanowires were employed in hybrid structures consisting of highly interconnected SnO₂ nanowire matrix coated with TiO₂ nanoparticles, which showed an open circuit voltage of 720 mV and an efficiency of 4.1% compared to 2.1% obtained with pure SnO₂ nanowire matrix. The electron transport time constants for SnO₂ nanowire matrix were an order of magnitude lower and the recombination time constants are about 100 times higher than that of TiO₂ nanoparticles. The higher efficiency observed for DSSCs based on hybrid structure is attributed to the band edge positions of SnO₂ relative to that of TiO₂ and faster electron transport in SnO₂ nanowires.     

电磁脉冲对太阳电池的损伤效应研究

针对电磁脉冲对太阳电池造成的损伤效应,通过器件-电路联合仿真的方法,在建立硅太阳电池单元器件模型的基础上,分析研究了在阶跃脉冲电压的注入下,太阳电池性能的退化情况.结果表明:在电压幅值一定时,上升时间存在一临界值,当上升时间大于这一临界值时,太阳电池的性能退化是可恢复的,小于这一临界值时,太阳电池短路电流和开路电压将迅速衰减,填充因子也随之减小,电池部分失效甚至全部毁坏.在上升时间一定时,不同幅值的电压都会使得电池的短路电流和开路电压下降,但相对于开路电压,短路电流的下降并不显著,当电压幅值大于某一值时,开路电压下降趋于加快,随着电压幅值的不断增加,太阳电池将被击穿,从而完全失效.     

Enhanced photovoltaic performance of dye sensitized solar cell using TiO2 and ZnO nanoparticles on top of free standing TiO2 nanotube arrays

Photovoltaic performance of dye sensitized solar cell (DSSC) with absorber layer of TiO₂ nanotube (NT)/TiO₂ nanoparticles (NPs)/ZnO NPs was investigated. Fabricated DSSC exhibits enhanced open circuit voltage, current density and power conversion efficiency compared with DSSC having absorber layer of TiO₂ NT/ TiO₂ NPs and TiO₂ NT/ZnO NPs. To further explore the dynamics of charge transport and recombination processes, electrochemical impedance analysis, intensity modulated photovoltage spectroscopy and photocurrent spectroscopy were carried out on the fabricated DSSCs. It was found that an optimal combination of TiO₂/ZnO NPs on top of TiO₂ NTs reduces the electron recombination and improves transport pathways, resulting in an efficient charge collection of 99%.     

A 21.5% efficient Cu(In,Ga)Se2 thin‐film concentrator solar cell

Cu(In,Ga)Se₂ (CIGS) solar cells have been designed for operation under mildly concentrated sunlight. The absorber was deposited via a three‐stage evaporation process that has consistently yielded high‐performance one‐sun devices. The device structure reported here was modified by reducing the thickness of the CdS window/buffer layer to enhance the short‐circuit current at the expense of the open‐circuit voltage. Operation of the devices under optical enhancement leads to significant increases in the voltage and fill factor. At 14 suns, the open‐circuit voltage for this device was 736 mV, the fill factor was 80.5%, and the efficiency was 21.5%. This result represents the first report of a polycrystalline thin‐film solar cell with an efficiency in excess of 20%. Published in 2002 by John Wiley & Sons, Ltd.     

Biohybrid Photoprotein‐Semiconductor Cells with Deep‐Lying Redox Shuttles Achieve a 0.7 V Photovoltage

Photosynthetic proteins transduce sunlight into biologically useful forms of energy through a photochemical charge separation that has a close to 100% quantum efficiency, and there is increasing interest in their use as sustainable materials in biohybrid devices for solar energy harvesting. This work explores a new strategy for boosting the open circuit voltage of photoelectrochemical cells based on a bacterial photosynthetic pigment‐protein by employing highly oxidizing redox electrolytes in conjunction with an n‐type silicon anode. Illumination generates electron–hole pairs in both the protein and the silicon electrode, the two being connected by the electrolyte which transfers electrons from the reducing terminal of the protein to photogenerated holes in the silicon valence band. A high open circuit voltage of 0.6 V is achieved with the most oxidizing electrolyte 2,2,6,6‐tetramethyl‐1‐piperidinyloxy, and this is further improved to 0.7 V on surface modification of the silicon electrode to increase its surface area and reduce reflection of incident light. The photovoltages produced by these biohybrid protein/silicon cells are comparable to those typical of silicon heterojunction and dye‐sensitized solar cells.     

Trap‐Assisted Recombination via Integer Charge Transfer States in Organic Bulk Heterojunction Photovoltaics

Organic photovoltaics are under intense development and significant focus has been placed on tuning the donor ionization potential and acceptor electron affinity to optimize open circuit voltage. Here, it is shown that for a series of regioregular‐poly(3‐hexylthiophene):fullerene bulk heterojunction (BHJ) organic photovoltaic devices with pinned electrodes, integer charge transfer states present in the dark and created as a consequence of Fermi level equilibrium at BHJ have a profound effect on open circuit voltage. The integer charge transfer state formation causes vacuum level misalignment that yields a roughly constant effective donor ionization potential to acceptor electron affinity energy difference at the donor–acceptor interface, even though there is a large variation in electron affinity for the fullerene series. The large variation in open circuit voltage for the corresponding device series instead is found to be a consequence of trap‐assisted recombination via integer charge transfer states. Based on the results, novel design rules for optimizing open circuit voltage and performance of organic bulk heterojunction solar cells are proposed.     

Nanoparticle/Dye Interface Optimization in Dye‐Sensitized Solar Cells

A critical component in the development of highly efficient dye‐sensitized solar cells is the interface between the ruthenium bipyridyl complex dye and the surface of the mesoporous titanium dioxide film. In spite of many studies aimed at examining the detailed anchoring mechanism of the dye on the titania surface, there is as yet no commonly accepted understanding. Furthermore, it is generally believed that a single monolayer of strongly attached molecules is required in order to maximize the efficiency of electron injection into the semiconductor. In this study, the amount of adsorbed dye on the mesoporous film is maximised, which in turn increases the light absorption and decreases carrier recombination, resulting in improved device performance. A process that increases the surface concentration of the dye molecules adsorbed on the TiO₂ surface by up to 20% is developed. This process is based on partial desorption of the dye after the initial adsorption, followed by readsorption. This desorption/adsorption cycling process can be repeated multiple times and yields a continual increase in dye uptake, up to a saturation limit. The effect on device performance is directly related and a 23% increase in power conversion efficiency is observed. Surface enhanced Raman spectroscopy, infrared spectroscopy, and electrochemical impedance analysis were used to elucidate the fundamental mechanisms behind this observation.     

Characterization of two new (A–π)2–D–A type dyes with different central D unit and their application for dye sensitized solar cells

We report the photophysical, electrochemical and theoretical properties of two dyes with same acceptor, π-linker and anchoring acceptor unit and different TPA (D1) and pyran (D2) donor central unit. The change in the central unit resulted in corresponding different photophysical and electrochemical properties. The dye sensitized solar cell fabricated using dye D1 showed the higher incident photon to current efficiency of 54%, a short circuit current (J_sc) of 11.86 mA/cm², an open circuit voltage of 0.64 V, and fill factor (FF) of 0.68, corresponding an overall power conversion efficiency of 5.16% which is higher than that for D2 based DSSCs (4.42%). The difference in the PCE of DSSCs based on D1 and D2 is partly, due to the smaller amount of dye loading, higher dark current and charge recombination rate of D1 based DSSC. The electrochemical spectra of DSSCs demonstrated longer electron life time and charge recombination resistance and small charge transport resistance for D1 sensitized DSSC, results the higher PCE.     

Non‐Geminate Recombination as the Primary Determinant of Open‐Circuit Voltage in Polythiophene:Fullerene Blend Solar Cells: an Analysis of the Influence of Device Processing Conditions

The physical origin of the open‐circuit voltage in bulk heterojunction solar cells is still not well understood. While significant evidence exists to indicate that the open‐circuit voltage is limited by the molecular orbital energies of the heterojunction components, it is clear that this picture is not sufficient to explain the significant variations which often occur between cells fabricated from the same heterojunction components. We present here an analysis of the variation in open‐circuit voltage between 0.4–0.65 V observed for a range of P3HT/PCBM solar cells where device deposition conditions, electrode structure, active‐layer thickness and device polarity are varied. The analysis quantifies non‐geminate recombination losses of dissociated carriers in these cells, measured under device operating conditions. It is found that at open‐circuit, losses due to non‐geminate recombination are sufficiently large that other loss pathways may effectively be neglected. Variations in open‐circuit voltage between different devices are shown to arise from differences in the rate coefficient for non‐geminate recombination, and from differences in the charge densities in the photoactive layer of the device. The origin of these differences is discussed, particularly with regard to variations in film microstructure. By separately quantifying these differences in rate coefficient and charge density, and by application of a simple physical model based upon the assumption that open‐circuit is reached when the flux of charge photogeneration is matched by the flux of non‐geminate recombination, we are able to calculate correctly the open‐circuit voltage for all the cells studied to within an accuracy of ±5 mV.     

Highly efficient dye‐sensitized solar cells using phenothiazine derivative organic dyes

Two novel organic dyes have been synthesized using electron rich phenothiazine as electron donors and oligothiophene vinylene as conjugation spacers. The two dyes (2E)‐2‐cyano‐3‐(5‐(5‐((E)‐2‐(10‐(2‐ethylhexyl)‐10H‐phenothiazin‐7‐yl)vinyl)thiophen‐2‐yl)thiophen‐2‐yl)acrylic acid (PTZ‐1) and (2E)‐3‐(5‐(5‐(4,5‐bis((E)‐2‐(10‐(2‐ethylhexyl)‐10H‐phenothiazin‐3‐yl)vinyl)thiophen‐2‐yl)thiophen‐2‐yl)thiophen‐2‐yl)‐2‐cyanoacrylic acid (PTZ‐2) were fully characterized and employed in dye‐sensitized solar cells (DSCs) to explore the effect of disubstituted donors on photovoltaic (PV) performance. The solar cells sensitized by the PTZ1 dye have a high IPCE plateau of 80% and achieve a short‐circuit photocurrent density of 12.98 mA/cm², an open‐circuit voltage of 0.713 V, and a fill factor (ff) of 66.6%, corresponding to a conversion efficiency of 6.17% under AM 1.5 100 mW/cm² illumination. The different performance of the solar cells based on the two dyes can be understood from the studies of the electron kinetics by electrochemical impedance spectroscopy (EIS). These investigations reveal that disubstituted donors in the organic sensitizers of three or more conjugation units deteriorate the PV performance due to enhanced recombination. Copyright © 2010 John Wiley & Sons, Ltd.     

Coumarin based sensitizers with ortho-halides substituted phenylene spacer for dye sensitized solar cells

The performance of DSSCs (dye sensitized solar cells) with a new series of dyes having different halide groups (i.e. F, Cl and Br) on o-position substituted phenyl spacers with same coumarin donor moieties have been reported. Optical, electrochemical, molecular orbital and photovoltaic properties were studied by varying the halide groups using these dyes. The replacement of halide atoms in same coumarin based dye had a significant effect on the short circuit current density (J_sc), open circuit voltage (V_oc), and photo conversion efficiency (PCE). The J_sc and PCE of dye CD-1 (fluorine substituted) are 10.3 mA/cm² and 5.2% respectively, which is higher than CD-2 (chlorine substituted) and CD-3 (bromine substituted) dyes (having PCE 4.1% and 3.5% respectively) devices. The optimized geometry calculation of o-halide phenyl π-spacer dyes were ascertained by density functional theory (DFT) using the B3LYP/6-31G(d,p) basis set. Moreover, we have checked the effect of various substituents in the same dye structure by DFT analysis.     

Nanosized Anatase TiO2 Single Crystals with Tunable Exposed (001) Facets for Enhanced Energy Conversion Efficiency of Dye‐Sensitized Solar Cells

This paper reports the synthesis of nanosized TiO₂ single crystals with different percentages of exposed (001) facets in the presence of HF solution. Various characterizations are conducted to understand the correlation between particle morphology, exposed (001) facets and photo‐conversion efficiency of the nanosized anatase TiO₂ single crystals. An enhancement in dye‐sensitized solar cells (DSSCs) overall conversion efficiency is observed for the photoanode consisting of nanosized TiO₂ single crystals with higher percentage of exposed (001) facets, increasing from 7.47%, 8.14% to 8.49% for the TiO₂ single crystals with ca. 10%, 38%, and 80% percentage of exposed (001) facets. Experimentally confirmed by dark current potential and open‐circuit voltage decay scans, such highly exposed (001) facets are not only favorable for more dye adsorption but also effectively retard the charge recombination process in DSSCs.     

染料敏化纳米晶TiO2太阳能电池

介绍了染料敏化纳米晶TiO2太阳能电池的结构,工作原理,技术指标以及TiO2纳米膜的制备方法.阐述了敏化纳米晶太阳能电池相比于硅太阳电池的低成本及优于其它光电化学电池的关键技术.讨论了影响NPC电池总的光电转换效率的因素,并对有机染料和无机染料光敏化剂的选择及染料的敏化问题进行了论述,在此基础上提出了将其商业化的一些值得深入研究和需要解决的问题.     

Synergistic Interaction of Dyes and Semiconductor Quantum Dots for Advanced Cascade Cosensitized Solar Cells

A new procedure for the cosensitization with quantum dots (QDs) and dyes for sensitized solar cells is reported here. Cascade cosensitization of TiO₂ electrodes is obtained by the sensitization with CdS QDs and zinc phthalocyanines (ZnPcs), in which ZnPcs containing a sulfur atom are specially designed to produce a cascade injection by direct attachment to QDs. This strategy causes a double synergetic interaction. This is the differentiating point of cascade cosensitization in comparison with other approaches in which dyes with conventional functionalization are anchored to TiO₂ electrodes. Cosensitization produces a panchromatic response from the visible to near‐IR region already observed with other sensitization strategies. However, cascade cosensitization produces in addition a synergistic interaction between QDs and dye, that it is not merely limited to the complementary light absorption, but dye enhances the efficiency of QD sensitization acting as a passivating agent. The cascade cosensitization concept is demonstrated with using [Co(phen)₃]^3+/2+ redox electrolyte. The TiO₂/CdS QD‐ZnPc/[Co(phen)₃]^3+/2+ sensitized solar cell shows a large improvement of short‐circuit photocurrent and open‐circuit voltage in comparison with samples just sensitized with QDs. The advent of such cosensitized QD‐ZnPc solar cells paves the way to extend the absorbance region of the promising QD‐based solar cells and the development of a new family of molecules designed for this purpose.     

Pseudomorphic HEMT manufacturing technology for multifunctionalKa-band MMIC applications

We have demonstrated very good performance, high yield Ka-band multifunctional MMIC results using our recently developed 0.25-μm gate length pseudomorphic HEMT (PHEMT) manufacturing technology. Four types of MMIC transceiver components-low noise amplifiers, power amplifiers, mixers, and voltage controlled oscillators-were processed on the same PHEMT wafer, and all were fabricated using a common gate recess process. High performance and high producibility for all four MMIC components was achieved through the optimization of the device epitaxial structure, a process with wide margins for critical process steps and circuit designs that allow for anticipated process variations, resulting in significant performance margins. We obtained excellent results for the Ka-band power amplifier: greater than 26 dBm output power at center frequency with 4.0% standard deviation over the 3-in. wafer, 2-GHz bandwidth, greater than 20 pet-cent power-added efficiency, over 8 dB associated gain, and over 10 dB linear gain. The best performance for the Ka-band LNA was over 17 dB gain and 3.5 dB noise figure at Ka-band. In this paper, we report our device, process, and circuit approach to achieve the state-of-the-art performance and producibility of our MMIC chips