Carbon Nanotubes for Dye‐Sensitized Solar Cells

As one type of emerging photovoltaic cell, dye‐sensitized solar cells (DSSCs) are an attractive potential source of renewable energy due to their eco–friendliness, ease of fabrication, and cost effectiveness. However, in DSSCs, the rarity and high cost of some electrode materials (transparent conducting oxide and platinum) and the inefficient performance caused by slow electron transport, poor light‐harvesting efficiency, and significant charge recombination are critical issues. Recent research has shown that carbon nanotubes (CNTs) are promising candidates to overcome these issues due to their unique electrical, optical, chemical, physical, as well as catalytic properties. This article provides a comprehensive review of the research that has focused on the application of CNTs and their hybrids in transparent conducting electrodes (TCEs), in semiconducting layers, and in counter electrodes of DSSCs. At the end of this review, some important research directions for the future use of CNTs in DSSCs are also provided.     

染料敏化太阳能电池无FTO煤基炭对电极的研究

分别以气煤、焦煤、瘦煤为原料制备了低成本、高性能煤基炭对电极(counter electrodes, CEs), 并使用煤基炭CE同时代替导电玻璃基底和催化层, 分别考察了浸渍和表面修饰对煤基炭CE结构和光电性能的影响。采用X射线衍射、扫描电镜和电化学阻抗谱等表征手段, 对煤基炭CE的结构和性能进行了表征。结果表明: 浸渍后煤基炭CE形成了底层致密表层多孔的一体化结构; 经过表面修饰的煤基炭CE表现出良好的光电性能, 其开路电压(V_oc)、短路电流密度(J_sc)和填充因子(FF)分别为0.79 V、13.48 mA/cm²和0.67, 光电转化效率(η)达到了7.16%, 与传统Pt电极的效率相当, 比石墨电极效率提高30%。煤基炭CE是传统Pt/FTO电极的良好替代材料。     

High Electrocatalytic and Wettable Nitrogen‐Doped Microwave‐Exfoliated Graphene Nanosheets as Counter Electrode for Dye‐Sensitized Solar Cells

In this paper, high electrocatalytic and wettable nitrogen‐doped microwave‐exfoliated graphene (N‐MEG) nanosheets are used as Pt‐free counter electrode (CE) for dye‐sensitized solar cells (DSSCs). A low cost solution‐based process is developed by using cyanamide (NH₂CN) at room temperature and normal pressure. The pyrrolic and pyridinic N atoms are doped into the carbon conjugated lattice to enhance electrocatalytic activity. N‐MEG film having N‐doping active sites and large porosity provides a wettable surface to facilitate electrolyte diffusion so that improves fill factor. Moreover, the control of the air exposure time after completing N‐MEG film is found to be crucial to obtain a reliable N‐MEG CE. A high DSSC efficiency up to 7.18% can be achieved based on N‐MEG CE, which is nearly comparable to conventional Pt CE.     

Pt‐Free Counter Electrode for Dye‐Sensitized Solar Cells with High Efficiency

Dye‐sensitized solar cells (DSSCs) have attracted widespread attention in recent years as potential cost‐effective alternatives to silicon‐based and thin‐film solar cells. Within typical DSSCs, the counter electrode (CE) is vital to collect electrons from the external circuit and catalyze the I₃^? reduction in the electrolyte. Careful design of the CEs can improve the catalytic activity and chemical stability associated with the liquid redox electrolyte used in most cells. In this Progress Report, advances made by our groups in the development of CEs for DSSCs are reviewed, highlighting important contributions that promise low‐cost, efficient, and robust DSSC systems. Specifically, we focus on the design of novel Pt‐free CE catalytic materials, including design ideas, fabrication approaches, characterization techniques, first‐principle density functional theory (DFT) calculations, ab‐initio Car‐Parrinello molecular dynamics (CPMD) simulations, and stability evaluations, that serve as practical alternatives to conventional noble metal Pt electrodes. We stress the merits and demerits of well‐designed Pt‐free CEs, such as carbon materials, conductive polymers, transition metal compounds (TMCs) and their corresponding hybrids. Also, the prospects and challenges of alternative Pt catalysts for their applications in new‐type DSSCs and other catalytic fields are discussed.     

Metal Oxide Semiconductors for Dye‐ and Quantum‐Dot‐Sensitized Solar Cells

This Review provides a brief summary of the most recent research developments in the synthesis and application of nanostructured metal oxide semiconductors for dye sensitized and quantum dot sensitized solar cells. In these devices, the wide bandgap semiconducting oxide acts as the photoanode, which provides the scaffold for light harvesters (either dye molecules or quantum dots) and electron collection. For this reason, proper tailoring of the optical and electronic properties of the photoanode can significantly boost the functionalities of the operating device. Optimization of the functional properties relies with modulation of the shape and structure of the photoanode, as well as on application of different materials (TiO₂, ZnO, SnO₂) and/or composite systems, which allow fine tuning of electronic band structure. This aspect is critical because it determines exciton and charge dynamics in the photoelectrochemical system and is strictly connected to the photoconversion efficiency of the solar cell. The different strategies for increasing light harvesting and charge collection, inhibiting charge losses due to recombination phenomena, are reviewed thoroughly, highlighting the benefits of proper photoanode preparation, and its crucial role in the development of high efficiency dye sensitized and quantum dot sensitized solar cells.     

One‐Step Hydrothermal Tailoring of NiCo2S4 Nanostructures on Conducting Oxide Substrates as an Efficient Counter Electrode in Dye‐Sensitized Solar Cells

A one‐step in situ tailoring of NiCo₂S₄ nanostructures is demonstrated on fluorine‐doped tin oxide (FTO) as Pt‐free counter electrodes (CEs) for dye‐sensitized solar cells (DSSCs) with performance surpassing that of a conventional Pt‐sputtered CE. An interconnected NiCo₂S₄ nanosheet network is successfully constructed on the FTO glass via a hydrothermal method, attributed to the synergistic effect of structure‐directing hexamethylenetetramine and L‐cysteine. A growth mechanism is proposed, and the effects of nanostructures and sulfur atomic percentages on the electrocatalytic performance are discussed in depth. A DSSC with the optimized interconnected NiCo₂S₄ nanosheet CE exhibits higher power conversion efficiency (7.22%) compared to that with a conventional Pt‐sputtered CE (6.87%) due to excellent charge transport properties and enhanced electrocatalytic activity of the NiCo₂S₄ nanostructures. This work showcases the strong potential of nanostructured ternary chalcogenides, which are composed of earth‐abundant elements and prepared through a single‐step hydrothermal process without tedious posttreatments, to reduce the dependence of platinum in DSSCs and other electrochemical devices.     

Edge‐Functionalized Graphene Nanoplatelets as Metal‐Free Electrocatalysts for Dye‐Sensitized Solar Cells

A scalable and low‐cost production of graphene nanoplatelets (GnPs) is one of the most important challenges for their commercialization. A simple mechanochemical reaction has been developed and applied to prepare various edge‐functionalized GnPs (EFGnPs). EFGnPs can be produced in a simple and ecofriendly manner by ball milling of graphite with target substances (X = nonmetals, halogens, semimetals, or metalloids). The unique feature of this method is its use of kinetic energy, which can generate active carbon species by unzipping of graphitic C? C bonds in dry conditions (no solvent). The active carbon species efficiently pick up X substance(s), leading to the formation of graphitic C? X bonds along the broken edges and the delamination of graphitic layers into EFGnPs. Unlike graphene oxide (GO) and reduced GO (rGO), the preparation of EFGnPs does not involve toxic chemicals, such as corrosive acids and toxic reducing agents. Furthermore, the prepared EFGnPs preserve high crystallinity in the basal area due to their edge‐selective functionalization. Considering the available edge X groups that can be selectively employed, the potential applications of EFGnPs are unlimited. In this context, the synthesis, characterizations, and applications of EFGnPs, specifically, as metal‐free carbon‐based electrocatalysts for dye‐sensitized solar cells (DSSCs) in both cobalt and iodine electrolytes are reviewed.