Aqueous dye-sensitized solar cell based on new ruthenium diphenyl carbazide complexes

The major challenge of the operation of every solar cell based on dye including water splitting solar cell (WSSC) and dye sensitized solar cell (DSSC) is the using organic solvent medium which causes to decompose the solar cell structure, resulting environmental impact. Here, we synthesized and characterized two new ruthenium complexes with nitrogen and oxygen donor ligands for DSSC application which show good stability on TiO₂ surface in water solvent. Interestingly, the DSSC based on [Ru(dcbpy)₂(DPC)]Cl, where dcbpy = 4,4-dicarboxilic acid 2,2-bipyridin and DPC = diphenylcarbazide, was shown better efficiency in water than methanol dye loading as well as N3 as a benchmark sensitizer in the same condition. The DPC-based exhibited open circuit voltage (V_oc) of 0.63 V, short-circuit current density (J_sc) of 2.5 mA/cm² and fill factor (FF) of 70%, resulting an overall power efficiency of 1.12%. The incident-photon-to-current conversion efficiency (IPCE) value is also reached to 45% for [Ru(dcbpy)₂(DPC)]Cl in the same condition It is proposed that the ruthenium complex containing nitrogen and oxygen donor ligands is more stability on TiO₂ and prevent the decomposition of TiO₂ porous under water solvent condition.     

A simplified electrical model of the dye-sensitised photoelectrochemical cell

This paper presents a steady-state electrical model of dye-sensitised solar cells with simplified boundary conditions. The codes are considerably concise and the sub-functions had confirmed good extensibility. This model is utilised to predict the current–voltage characteristics and the energy conversion efficiency based on various design and operating properties. The experimental data from the literature have been used to validate the theoretically fitted j?V characteristics of the presented model. Parametric simulations were conducted to analyse the effect of diffusion/drift, dye loading, and electrode thickness on dye-sensitised solar cell performance. Simulated results confirm that diffusion is the major driving force for electron and ion transport, while the drift of electrons is negligible. The model predicts optimal electrode thickness ranging between 10 and 15° μm which is consistent with the thickness (10 μm) used in general experimental studies published in the literature. Additionally, it is observed that there exists a logarithmic relation between the short-circuit current density and the amount of dye adsorption. This observation suggests that there exists a dominated recombination reaction which is responsible towards the high efficiency of DSCs.     

SOLAR CELLS IN THIN EPITAXIAL LAYERS ON METALLURGICAL SILICON SUBSTRATES

Conversion efficiencies of 11.5-12% have been obtained for solar cells with an active layer epitaxially grown on upgraded metallurgical grade silicon substrates made by industry. An epilayer thickness of 30 μm was shown to be sufficient if the substrate doping is much larger than the epilayer doping. Spectral response measurements, fitted to simple models, showed that:

? the electron diffusion length reached 120 μm in the epilayer,

? a back surface field was efficient in increasing collection efficiency,

? Optical path enhancement due to texturisation decreased absorption losses.

These results were confirmed by modeling of the short circuit current and open circuit voltage of the cells.

Economic viability is discussed. The results can also be used to increase the efficiency of conventional solar cells built on thin wafers (< 150μm).     

Photogalvanic effect of Brilliant Cresyl Blue–Fructose– surfactant–small Pt electrode-artificial light: Simultaneous solar energy conversion and storage

The photogalvanic effect of Brilliant Cresyl Blue–Fructose system is reported in the presence of efficiency enhancer chemical such as surfactant (Sodium Lauryl Sulfate) and small Pt electrode for solar energy conversion and storage in artificial light. The study has shown enhanced performance in terms of electrical parameters such as maximum power (291.2 μW), short-circuit current (1,120 μA), open-circuit potential (1,045 mV), efficiency (8.4%), and storage capacity as half change time (140 min).     

PVDF基准固态染料敏化太阳电池的研究

以聚偏氟乙烯(PVDF)为凝胶剂,分别将有机溶剂、离子液体电解质固化,并采用这两种体系的电解质分别封装成染料敏化太阳电池,测试了凝胶剂的加入量对太阳电池光电特性的影响,同时利用交流阻抗谱分析了聚合物的加入对抑制暗电流的作用。其中,有机溶剂电解质中PVDF的质量分数分别为5%、20%、25%;离子液体(甲基-丙基咪唑,MPII)电解质中PVDF的质量分数分别为0%、1%、10%。实验中制备的准固态小面积(0.25cm~2)封装电池光电转换效率均高于5.3%,PVDF含量为25%的有机溶剂型准固态电池的效率达到5.92%。此外,实验中还制备了密封的1cm~2的准固态电解质电池,并获得了6.26%的效率,此时对应的J_(SC)=15.4mA/cm~2,V_(OC)=0.672V,FF=60.5%。     

Modeling and simulation of solar cells quantum well based on SiGe/Si

In recent years, the development of quantum well solar cells QWSCs (Quantum Well Solar Cells) has generated a great deal of interest. These configurations have shown good promise to optimize the low conversion efficiency of conventional solar cells because of the high rate of absorption losses present in them. In this work, we are interested in modeling and simulation of two different structures of solar cells, a simple solar cell based on silicon Si and a quantum well solar cell SiGe/Si. When a solar cell is compared to 80 quantum well layers of Si_0.8Ge_0.2with a pin solar cell based on Si. The short circuit current J_sc increases from 23.55 to 37.48 mA/cm² with a relative increase of 59.15% found. In addition, the limit of the absorption band of the lower energy photons extends from 1100 nm to 2000 nm.     

Electrospun Co-TiC nanoparticles embedded on carbon nanofibers: Active and chemically stable counter electrode for methanol fuel cells and dye-sensitized solar cells

Cobalt-titanium carbide nanoparticles (Co-TiC NPs) embedded on carbon nanofibers (composite) were prepared by electrospinning of a solution containing cobalt acetate tetrahydrate (CoAc), titanium (IV) isopropoxide (TIIP) and polyvinylpyrrolidone (PVP) in acetic acid and ethanol. It was then subjected to a carbonation process at a low temperature (850 °C) since the composite contains metal carbide. The obtained composite, as an efficient electrode, was used as an alternative to Pt-free counter electrode (CE) for fuel cells (FCs) and dye-sensitized solar cells (DSSCs). Cyclic voltammetry (CV) and chronoamperatory (CA) tests were used to measure the composite electrode's performance in methanol oxidation. The results showed that the introduced composite could enhance both methanol electro-oxidation and electrochemical stability as the low onset potential and high current density of the composite electrode were obtained at 189 mV and ～90 mA cm^?2 vs. Ag/AgCl, respectively. The composite also was examined in dye-sensitized solar cells as counter electrode (CE). The results showed that the composite electrode was effective, providing stable electrocatalytic activity (ECA) and conductivity, indicating the composite can improve catalytic activity in triiodide reduction. The short-circuit current density (J_sc), open circuit voltage (V_OC), fill factor (FF), and energy conversion efficiency (η) were found to be ～9.98 mA cm^?2, 0.758 V, 0.507 and 3.87%, respectively. The high ECA could be attributed to the synergic effects from all the pristine components.     

The effect of front pyramid heights on the efficiency of homogeneously textured inline-diffused screen-printed monocrystalline silicon wafer solar cells

The majority of industrial monocrystalline silicon (c-Si) wafer solar cells are alkaline textured (at least the illuminated surface) to reduce reflection and increase absorption of incident light. Therefore, understanding the influence of front pyramid heights on the solar cell parameters is essential for further improving cell efficiency. In this work we report the impact of pyramid height on the performance of inline-diffused c-Si solar cells. Three alkaline texture processes with potassium silicate additives are optimised to result in homogeneous coverage of pyramids. By modifying the process, surface textures with small (∼5 μm maximum), medium (∼6 μm maximum) and large (∼8 μm maximum) pyramid heights are formed. The impact of pyramid size on cell parameters is experimentally studied using industrial-grade 156-mm pseudo-square p-type Czochralski wafers. It is found that within the pyramid size range studied here, there is no significant variation in effective minority carrier lifetime, reflectance, open-circuit voltage or short-circuit current. However, fill factor and hence efficiency is significantly impacted by pyramid size. While cells in all three groups demonstrate high fill factor (>79%), it is shown that an average fill factor gain of up to 1% absolute can be achieved by using the best-suited texture process.     

Oxide/polymer interfaces for hybrid and organic solar cells: Anatase vs. Rutile TiO2

In this work, we study the effect of the transparent conducting oxide (TCO) and the polymer applied (MEH-PPV or P3HT) on the photovoltaic properties of TCO/TiO₂/polymer/Ag bi-layer solar cells. The solar cells were analyzed under inert atmosphere conditions resembling an encapsulated or sealed device. We demonstrate that the substrate applied, ITO or FTO, modifies the crystalline structure of the TiO₂: on an ITO substrate, TiO₂ is present in its anatase phase, on an FTO, the rutile phase predominates. Devices fabricated on an FTO, where the rutile phase is present, show better stability under inert atmospheres than devices fabricated on an ITO, anatase phase. With respect to the polymer, devices based on MEH-PPV show higher Voc (as high as 1 V), while the application of P3HT results in lower Voc, but higher J_sc and longer device stability. These observations have been associated to (a), the crystalline structure of TiO₂ and (b) to the form the polymer is bonded to the TiO₂ surface. In-situ IPCE analyses of P3HT-based solar cells show a red shift on the peak corresponding to TiO₂, which is not present on the MEH-PPV-based solar cells. The latter suggest that P3HT can be linked to the TiO₂ though the S-end atom, which results in devices with lower Voc. All these observations are also valid for devices, where the bare TiO₂ is replaced by an Nb-TiO₂. The application of an Nb-TiO₂ with rutile structure in these polymer/oxide solar cells is the reason for their higher stability under inert atmospheres. We conclude that the application of TiO₂ in its rutile phase is beneficial for long-term stability devices. Moreover there is an interplay between low Voc and J_sc in devices applying P3HT, since power conversion efficiency can be partially canceled by their lower Voc in comparison with MEH-PPV. These findings are important for polymer/oxide solar cells, but also for organic solar cells, where a layer of semiconductor oxides are in direct contact with a polymer, like in an inverted or tandem organic solar cells.     

微晶硅电池的制备及提高其效率的优化

采用甚高频等离子体增强化学气相沉积(VHF-PECVD)技术制备了不同硅烷浓度系列的微晶硅电池。结果表明:电池的开路电压随着硅烷浓度的增大而逐渐增加,而电池的短路电流则先增加后减小,在转折点电池的效率达到最大,填充因子则变化不明显;(220)择优取向出现,I(220)/I(111)比值大,电池的短路电流密度也大,电池的效率也最高;在实验的范围内,电池的短路电流密度和厚度成正比例关系;首次在国内制备出了效率达7.3%,短路电流密度(Jsc)为21.7mA/cm2,开路电压(Voc)为0.52V,填充因子(FF)为65%的微晶硅电池。     

Development status of high-efficiency HIT solar cells

This paper describes the development status of high-efficiency heterojunction with intrinsic thin-layer (HIT) solar cells at SANYO Electric. Presently, the conversion efficiency of our standard HIT solar cell has reached a level of 23.0% for a practical size of (100.4 cm²) substrate. On the other hand, we have developed special technologies for effectively using thinner substrates for HIT solar cells. Surprisingly, we have achieved a quite high open circuit voltage (V_oc) of 743 mV, and a high conversion efficiency of 22.8% using only a 98-μm-thick substrate. A 98-μm-thick cell also exhibits a good temperature coefficient, and allows the thickness of the substrate to be reduced by more than 50% while maintaining its efficiency. These results suggest that the HIT solar cell has the potential to further improve cost-performance.     

Microsystems enabled photovoltaics: 14.9% efficient 14 μm thick crystalline silicon solar cell

Crystalline silicon solar cells 10-15 times thinner than traditional commercial c-Si cells with 14.9% efficiency are presented with modeling, fabrication, and testing details. These cells are 14 μm thick, 250 μm wide, and have achieved 14.9% solar conversion efficiency under AM 1.5 spectrum. First, modeling results illustrate the importance of high-quality passivation to achieve high efficiency in thin silicon, back contacted solar cells. Then, the methodology used to fabricate these ultra thin devices by means of established microsystems processing technologies is presented. Finally, the optimization procedure to achieve high efficiency as well as the results of the experiments carried out with alumina and nitride layers as passivation coatings are discussed.     

2019年中国光伏技术发展报告——新型太阳电池的研究进展(1)

详细介绍了2018年国内外在钙钛矿太阳电池、有机太阳电池、染料敏化太阳电池、量子点太阳电池等新型太阳电池方面的研究成果和产业化进展。     

ELECTRODEPOSITED CdTe FOR THIN FILM SOLAR CELLS

Large area 300 mm x 300 mm CdS/CdTe solar cells with record efficiencies over 10% have been fabricated using a reproducible, safe and low cost electrodeposition route for CdTe deposition. CdS window layers have been grown using chemical bath deposition which produces uniform adherent films by a cost effective route. Electrical characterization of small area (0.02 cm²) devices confirms that the structure is p-n rather than p-i-n. Module reliability tests show efficiency stability for more than 16,000 hours outside, and very little change using indoor environmental tests.     

Improvement on the long-term stability of flexible plastic dye-sensitized solar cells

We investigate the long-term stability of performance for plastic dye-sensitized solar cells (DSSCs) based on organic iodides (TBAI or PMII) in methoxypropionitrile-based electrolytes. Plastic DSSCs containing TBAI maintain 96.9% of baseline efficiency under more than 1000 h prolonged one sun light irradiation and thermal stress (60 °C) aging. The factors of device long-term stability, such as the effects of organic iodides, cell-sealing conditions, and the sheet resistance of indium tin oxide coated polyethylene naphthalate substrate (ITO/PEN) are discussed via using electrochemical impedance spectroscopy and electrical resistance measurement.     

New ultra thin CIGS structure solar cells using SCAPS simulation program

The present contribution reports on the performances of ultra thin chalcopyrite Cu (In,Ga) Se (CIGS) solar cells. An alternative ZnO/CdS/CIGS/Si structure has been proposed using solar cell capacitance simulator (SCAPS). The main idea behind this analysis is the improvement of the device efficiency using materials cheaper than conventional CIGS. For that purpose, a 1 μm of a new layer p-Si has been added. Various thicknesses of CIGS absorber layer ranging from 0.1 to 1 μm have been used. Our findings showed that the increase of the absorber layer thickness leads to the improvement of the performance of the new CIGS solar cells. It was found that the best structure must have a window layer ZnO, a buffer layer (CdS), an absorbent layer (CIGS) and a Si layer with thicknesses of 0.02, 0.05, 1 and 1 μm, respectively. Cells with these features give conversion efficiency of 21.3%. The present results showed that the new ultra thin CIGS solar cells structure has performance parameters that are comparable to those of the conventional ones with reduced cost.     

High-voltage (1.8 V) tandem solar cell system using a GaAs/AlXGa(1−X)As graded solar cell and dye-sensitised solar cells with organic dyes having different absorption spectra

Stacked multijunction (tandem) solar cells have been prepared by mechanically stacking dye-sensitised solar cells (DSCs) and a GaAs/Al_XGa_(1−X)As graded solar cell (GGC) as the top and bottom cells, respectively. Three organic dyes with different absorption spectra (D131, D102 and D205) were used in the DSCs, in order to match the photocurrent density between the DSC and the GGC. Tuning the absorption range of the DSC by choosing an appropriate dye, increased the overall photovoltaic conversion efficiency due to the optimal utilisation of the solar spectrum in the individual cells. The open circuit photovoltages (V_OC) of the GGC and the DSC with D131 were 1.11 V and 0.76 V, respectively, resulting in a V_OC of 1.85 V and a photovoltaic conversion efficiency of 7.63% for the tandem cell. Although the overall conversion efficiency has not exceeded that of the GGC (7.66%), these tandem cells provide adequate V_OC values for water splitting applications.     

Investigation on PEM water electrolysis cell design and components for a HyCon solar hydrogen generator

Hydrogen as a secondary energy carrier promises a large potential as a long term storage for fluctuating renewable energies. In this sense a highly efficient solar hydrogen generation is of great interest especially in southern countries having high solar irradiation. The patented Hydrogen Concentrator (HyCon) concept yields high efficiencies combining multi-junction solar cells with proton exchange (PEM) membrane water electrolysis. In this work, a special PEM electrolysis cell for the HyCon concept was developed and investigated. It is shown that the purpose-made PEM cell shows a high performance using a titanium hybrid fiber sinter function both as a porous transport layer and flow field. The electrolysis cell shows a high performance with 1.83 V at 1 A/cm² and 24 °C working under natural convection with a commercially available catalyst coated membrane. A theoretical examination predicts a total efficiency for the HyCon module from sunlight to hydrogen of approximately 19.5% according to the higher heating value.     

Role of graphene and transition metal dichalcogenides as hole transport layer and counter electrode in solar cells

Photovoltaic (PV) technology got much attention in the past few decades in developing advanced and environment friendly solar cells (SCs). However, high cost, unstable nature, and low efficiency are major limitations towards commercialization of SCs. To overcome the issues, two-dimensional materials (2DMs) have been exploited due to low cost, high catalytic activity, fast charge separation, and better electrochemical performance. The review emphasis on (a) the electrochemical performance of graphene and transition metal dichalcogenides (TMDCs) as a hole transport layer (HTL) in SCs and (b) to explore low-cost and effective counter electrode (CE) based on graphene and TMDCs for dye-sensitized solar cell (DSSC). The review presents a comparative analysis of 2DMs as HTL and CE to attain highly efficient and low-cost PV devices. Multiple combinations of the material with graphene, graphene oxide (GO), reduced graphene oxide (rGO), tungsten disulfide (WS₂), molybdenum disulfide (MoS₂) as HTL, and CE material in PV cells are discussed and comparatively analyzed. Numerous strategies are briefly discussed to enhance the efficiency of SCs by utilizing graphene and TMDCs based HTL and CEs. The review focuses on the recent progress in developing low-cost and highly efficient PV devices by using 2DMs. Our study reveals that GO/PEDOT:PSS demonstrate a maximum power conversion efficiency (PCE) of 13.1% when fabricated at different revolutions. Moreover, our statistical analysis unveils that efficiency of the cell can be enhanced by optimizing the layer thickness, which provide a route to develop highly efficient and better performance SCs that can be exploited for future commercial applications.     

Efficiency enhancement for bulk-heterojunction hybrid solar cells based on acid treated CdSe quantum dots and low bandgap polymer PCPDTBT

We report on the efficiency enhancement for bulk-heterojunction hybrid solar cells based on hexanoic acid treated trioctylphosphine/oleic acid-capped CdSe quantum dots (QDs) and low bandgap polymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) compared to devices based on poly(3-hexylthiophene) (P3HT). Photovoltaic devices with optimized polymer:QD weight ratio, photoactive film thickness, thermal annealing treatment, and cathode materials exhibited a power conversion efficiency of 2.7% after spectral mismatch correction, which is the highest reported value for spherical CdSe QD based photovoltaic devices. The efficiency enhancement is attributed to the surface treatment of the QDs together with the use of the low bandgap polymer PCPDTBT leading to an increased short-circuit current density due to additional light absorption between 650 and 850 nm. Our results suggest that the hexanoic acid treatment is generally applicable to various ligand-capped CdSe and confirm that low bandgap polymers with adequate HOMO and LUMO levels are promising to be incorporated into hybrid solar cells for further device performance improvement.