能源化学(英文版)

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Recent advances in rylene diimide polymer acceptors for all-polymer solar cells

Xin Guo, Dandan Tu, Xuan Liu

2015, 21(6): 675-685. DOI: 10.1016/j.jechem.2015.11.003

摘要 ( 5285 )

In recent years, a large library of n-type polymers have been developed and widely used as acceptor materials to replace fullerene derivatives in polymer solar cells (PSCs), stimulating the rapid expansion of research on so-called all-polymer solar cells (aPSCs). In particular, rylene diimide-based n-type polymer acceptors have attracted broad research interest due to their high electron mobility, suitable energy levels, and strong light-harvesting ability in the visible region. Among various polymer acceptors, rylene diimide-based polymers presented best performances when served as the acceptor materials in aPSCs. Typically, a record power conversion efficiency (PCE) of 7.7% was very recently achieved from an aPSC with a rylene diimide polymer derivative as the acceptor component. In this review, we highlight recent progress of n-type polymers originated from two significant classes of rylene diimide units, namely naphthalene diimide (NDI) and perylene diimide (PDI), as well as their derivatives for aPSC applications.

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Recent research progress on quasi-solid-state electrolytes for dye-sensitized solar cells

Asif Mahmood

2015, 21(6): 686-692. DOI: 10.1016/j.jechem.2015.10.018

摘要 ( 4684 )

Dye-sensitized solar cells (DSSCs) are the most promising, low cost and most extensively investigated solar cells. They are famous for their clean and efficient solar energy conversion. Nevertheless this, long-time stability is still to be acquired. In recent years research on solid and quasi-solid state electrolytes is extensively increased. Various quasi-solid electrolytes, including composites polymer electrolytes, ionic liquid electrolytes, thermoplastic polymer electrolytes and thermosetting polymer electrolytes have been used. Performance and stability of a quasi-solid state electrolyte are between liquid and solid electrolytes. High photovoltaic performances of QS-DSSCs along better long-term stability can be obtained by designing and optimizing quasi-solid electrolytes. It is a prospective candidate for highly efficient and stable DSSCs.

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Improving the interfacial contact between CH₃NH₃PbI_3-xCl_x and Au by LiTFSI solution treatment for efficient photoelectric devices

Xiang Xia, Hongcui Li, Yanhua Li, Cailong Liu, Xizhe Liu

2015, 21(6): 693-697. DOI: 10.1016/j.jechem.2015.10.005

摘要 ( 5689 )

Organic lead halide compounds with perovskite structure become a promising photovoltaic material for lowcost thin film solar cells in recent years. The property of perovskite/metal interface is a fundamental topic for the effective charge transfer at metal electrodes. In this work, we develop an interface modification method of lithium bis(trifluoromethane sulfonimide) (LiTFSI) solution treatment, which can effectively decrease the charge transfer resistance at the CH₃NH₃PbI_3-xCl_x/Au interface. After the solution treatment, uniform nanodots are formed at the surface of CH₃NH₃PbI_3-xCl_x films, and the barrier height at CH₃NH₃PbI_3-xCl_x/Au interface reduces from 0.51 V to 0.08 V. As a consequence, the efficiency of hole conductor free solar cells with CH₃NH₃PbI_3-xCl_x harvester increase from 4.0% to 7.6% under one sun condition. It is also found that the hole conductor free perovskite solar cell can work in a photodetector mode, which has the same output properties with phototransistors. After the LiTFSI solution treatment, the sensitivity of this photodetector can be improved for about one time.

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A novel phenoxazine-based hole transport material for efficient perovskite solar cell

Ming Cheng, Cheng Chen, Bo Xu, Yong Hua, Fuguo Zhang, Lars Kloo, Licheng Sun

2015, 21(6): 698-706. DOI: 10.1016/j.jechem.2015.10.021

摘要 ( 8422 )

Based on the previous research work in our laboratory, we have designed and synthesized a small-molecule, hole transport material (HTM) POZ6-2 using phenoxazine (POZ) as central unit and dicyanovinyl units as electron-withdrawing terminal groups. Through the introduction of a 2-ethyl-hexyl bulky chain into the POZ core unit, POZ6-2 exhibits good solubility in organic solvents. In addition, POZ6-2 possesses appropriate energy levels in combination with a high hole mobility and conductivity in its pristine form. Therefore, it can readily be used as a dopant-free HTM in perovskite solar cells (PSCs) and a conversion efficiency of 10.3% was obtained. The conductivity of the POZ6-2 layer can be markedly enhanced via doping in combination with typical additives, such as 4-tert-butylpyridine (TBP) and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI). Correspondingly, the efficiency of the PSCs was further improved to 12.3% using doping strategies. Under the same conditions, reference devices based on the well-known HTM Spiro-OMeTAD show an efficiency of 12.8%.

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A repeated interdiffusion method for efficient planar formamidinium perovskite solar cells

Huiyin Zhang, Jiangjian Shi, Juan Dong, Xin Xu, Yanhong Luo, Dongmei Li, Qingbo Meng

2015, 21(6): 707-711. DOI: 10.1016/j.jechem.2015.10.017

摘要 ( 5347 )

A repeated interdiffusion method is described for phase-stable and high-quality (FA,MA)PbI₃ film. The crystallization and growth of the perovskite films can be well controlled by adjusting the reactant concentrations. With this method, dense, smooth perovskite films with large crystals have been obtained. Finally, a PCE of 16.5% as well as a steady-state efficiency of 16.3% is achieved in the planar perovskite solar cell.

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Characterization of hot carrier cooling and multiple exciton generation dynamics in PbS QDs using an improved transient grating technique

Qing Shen, Kenji Katayama, Taro Toyoda

2015, 21(6): 712-716. DOI: 10.1016/j.jechem.2015.11.002

摘要 ( 4703 )

Multiple exciton generation (MEG) dynamics in colloidal PbS quantum dots (QDs) characterized with an improved transient grating (TG) technique will be reported. Only one peak soon after optical absorption and a fast decay within 1 ps can be observed in the TG kinetics when the photon energy of the pump light hν is smaller than 2.7E_g(E_g:band gap between LUMO and HOMO in the QDs), which corresponds to hot carrier cooling. When hν is greater than 2.7E_g, however, after the initial peak, the TG signal decreases first and soon increases, and then a new peak appears at about 2 to 3 ps. The initial peak and the new peak correspond to hot carriers at the higher excited state and MEG at the lowest excited state, respectively. By proposing a theoretical model, we can calculate the hot carrier cooling time constant and MEG occurrence time constant quantitatively. When MEG does not happen for hν smaller than 2.7E_g, hot carrier cools with a time constant of 400 fs. When MEG occurs for hν larger than 2.7E_g, hot carrier cools with a time constant as small as 200 fs, while MEG occurs with a time constant of 600 fs. The detailed hot carrier cooling and MEG occurrence dynamics characterized in this work would shed light on the further understanding of MEG mechanism of various type of semiconductor QDs.

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TiO₂ nanoparticle-based electron transport layer with improved wettability for efficient planar-heterojunction perovskite solar cell

Peng Chen, Yinglin Wang, Meiqi Wang, Xintong Zhang, Lingling Wang, Yichun Liu

2015, 21(6): 717-721. DOI: 10.1016/j.jechem.2015.10.014

摘要 ( 5763 )

The electron transport layer (ETL) plays an important role in planar heterojunction perovskite solar cell (PSCs), by affecting the light-harvesting, electron injection and transportation processes, and especially the crystallization of perovskite absorber. In this work, we utilized a commercial TKD-TiO₂ nanoparticle with a small diameter of 6 nm for the first time to prepare a compact ETL by spin coating. The packing of small-size particles endowed TKD-TiO₂ ETL an appropriate surface-wettability, which is beneficial to the crystallization of perovskite deposited via solution-processed method. The uniform and high-transmittance TKD-TiO₂ films were successfully incorporated into PSCs as ETLs. Further careful optimization of ETL thickness gave birth to a highest power conversion efficiency of 11.0%, which was much higher than that of PSC using an ETL with the same thickness made by spray pyrolysis. This TKD-TiO₂ provided a universal solar material suitable for the further large-scale production of PSCs. The excellent morphology and the convenient preparation method of TKD-TiO₂ film gave it an extensive application in photovoltaic devices.

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Effect of temperature on the efficiency of organometallic perovskite solar cells

Hua Zhang, Xianfeng Qiao, Yan Shen, Mingkui Wang

2015, 21(6): 729-735. DOI: 10.1016/j.jechem.2015.10.007

摘要 ( 7616 )

In recent years perovskite solar cells have attracted an increasing scientific and technological interest in the scientific community. It is important to know that the temperature is one of the factors which have a strong effect on the efficiency of perovskite solar cell. This study communicates a temperature analysis on the photovoltaic parameters of CH₃NH₃PbI₃-based perovskite solar cell in a broad interval from 80 to 360 K. Strong temperature-dependent photovoltaic effects have been observed in the type of solar cell, which could be mainly attributed to CH₃NH₃PbI₃, showing a ferroelectric-paraelectric phase transition at low temperature (T < 160 K). An increase in temperature over the room temperature decreased the perovskite solar cell performance and reduced its efficiency from 16% to 9%. The investigation with electronic impedance spectroscopy reveals that at low temperature (T < 120 K) the charge transport layer limits the device performance, while at high temperature (T > 200 K), the interfacial charge recombination becomes the dominant factor.

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In-situ fabrication of dual porous titanium dioxide films as anode for carbon cathode based perovskite solar cell

Xiaoli Zheng, Zhanhua Wei, Haining Chen, Yang Bai, Shuang Xiao, Teng Zhang, Shihe Yang

2015, 21(6): 736-743. DOI: 10.1016/j.jechem.2015.10.003

摘要 ( 5174 )

We develop a dual porous (DP) TiO₂ film for the electron transporting layer (ETL) in carbon cathode based perovskite solar cells (C-PSCs). The DP TiO₂ film was synthesized via a facile PS-templated method with the thickness being controlled by the spin-coating speed. It was found that there is an optimum DP TiO₂ film thickness for achieving an effective ETL, a suitable perovskite/TiO₂ interface, an efficient light harvester and thus a high performance C-PSC. In particular, such a DP TiO₂ film can act as a scaffold for complete-filling of the pores with perovskite and for forming high-quality perovskite crystals that are seamlessly interfaced with TiO₂ to enhance interfacial charge injection. Leveraging the unique advantages of DP TiO₂ ETL, together with a dense-packed and pinhole-free TiO₂ compact layer, PCE of the C-PSCs has reached 9.81% with good stability.

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Comparison of conventional and inverted structures in fullerene-free organic solar cells

Yifan Wang, Huitao Bai, Xiaowei Zhan

2015, 21(6): 744-749. DOI: 10.1016/j.jechem.2015.10.002

摘要 ( 5172 )

A n-type small molecule DC-IDT2F, with 4,4,9,9-tetrakis(4-hexylphenyl)-indaceno[1,2-b:5,6-b]dithiophene as a central building block, furan as π-bridges, and 1,1-dicyanomethylene-3-indanone as end acceptor groups, was synthesized and used as an electron acceptor in solution-processed organic solar cells (OSCs). DC-IDT2F exhibited good thermal stability, broad and strong absorption in 500-850 nm, a narrow bandgap of 1.54 eV, LUMO of-3.88 eV, HOMO of-5.44 eV and an electron mobility of 6.5×10^-4 cm²/(V·s). DC-IDT2F-based OSCs with conventional and inverted structures exhibited power conversion efficiencies of 2.26 and 3.08%, respectively. The effect of vertical phase separation and morphology of the active layer on the device performance in the two structures was studied.

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

Jue Chen, Xing Li, Wenjun Wu, Jianli Hua

2015, 21(6): 750-755. DOI: 10.1016/j.jechem.2015.10.004

摘要 ( 4760 )

A distinctive method is proposed by simply utilizing ultrasonic technique in TiO₂ 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 TiO₂ as well as higher cell efficiency than regular deposition, thus the fabrication time is markedly reduced. It is found that the device based on 40 kHz ultrasonic (within 1 h) with N719 exhibits a V_oc of 789 mV, J_sc of 14.94 mA/cm² and fill factor (FF) of 69.3, yielding power conversion efficiency (PCE) of 8.16%, which is higher than device regularly dyed for 12 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.

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Titanylphthalocyanine as hole transporting material for perovskite solar cells

Mengna Sun, Shirong Wang, Yin Xiao, Zhihao Song, Xianggao Li

2015, 21(6): 756-761. DOI: 10.1016/j.jechem.2015.10.020

摘要 ( 9352 )

Titanylphthalocyanine (TiOPc) as hole transporting material (HTM) was successfully synthesized by a simple process with low cost. Perovskite solar cells using the TiOPc as HTM were fabricated and characterized. TiOPc as HTM plays an important role in increasing the power conversion efficiency (PCE) by minimizing recombination losses at the perovskite/Au interface because TiOPc as HTM can extract photogenerated holes from the perovskite and then transport quickly these charges to the back metal electrode. In the research, the β-TiOPc gives a higher PCE than α-TiOPc for the devices due to sufficient transfer dynamics. The β-TiOPc was applied in perovskite solar cells without dopping to afford an impressive PCE of 5.05% under AM 1.5G illumination at the thickness of 40 nm which is competitive with spiro-OMeTAD at the same condition. The present work suggests a guideline for optimizing the photovoltaic properties of perovskite solar cells using the TiOPc as the HTM.

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Facile fabrication of TiO₂ nanoparticle-TiO₂ nanofiber composites by co-electrospinning-electrospraying for dye-sensitized solar cells

G. S. Anjusree, T. G. Deepak, Shantikumar V Nair, A. Sreekumaran Nair

2015, 21(6): 762-769. DOI: 10.1016/j.jechem.2015.11.001

摘要 ( 4527 )

We report a facile method for the fabrication of TiO₂ nanofiber-nanoparticle composite (FP) via. simultaneous electrospraying and electrospinning for dye-sensitized solar cell (DSC) applications. The loading of nanoparticles on the fibers is controlled by varying their feed rates during electrospinning. The FP composites having three different particle loading are prepared by the methodology and the FP with the highest particle loading (denoted as FP-3 in the manuscript) showed the best overall efficiency of 9.15% in comparison to the other compositions of the FP (FP-2, 8.15% and FP-1, 7.51%, respectively) and nanofibers (F) and nanoparticles (P) separately (7.21 and 7.81, respectively). All the material systems are characterized by spectroscopy, microscopy, surface area measurements and the devices are characterized by current-voltage (I-V), incident photon-to-current conversion efficiency (IPCE), electrochemical impedance measurements, etc. I-V, dye-loading and reflectance measurements throw light on the overall performance of the DSC devices.

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New tetrazole-based organic dyes for dye-sensitized solar cells

Zahra Jafari Chermahini, Alireza Najafi Chermahini, Hossein A Dabbagh, Abbas Teimouri

2015, 21(6): 770-778. DOI: 10.1016/j.jechem.2015.10.015

摘要 ( 6881 )

A series of new metal-free organic dyes that contain donors with triphenylamine or its derivatives and tetrazole-based acceptors were synthesized and characterized by photophysical, electrochemical, and theoretical computational methods. They were applied in nanocrystalline TiO₂ solar cells (DSSCs). It is found that the introduction of diphenylamine units as antennas in the as-synthesized dyes could improve photovoltaic performance compared with phenothiazine and carbazole units as antennas in DSSCs. The dye with (2H-tetrazol-5-yl) acrylonitrile electron acceptor also displayed the highest solar-to-electrical energy conversion efficiency.

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Synthesis and photophysical properties of donor-acceptor system based bipyridylporphyrins for dye-sensitized solar cells

Preeyanut Duanglaor, Preecha Thiampanya, Taweesak Sudyoadsuk, Vinich Promarak, Buncha Pulpoka

2015, 21(6): 779-785. DOI: 10.1016/j.jechem.2015.10.016

摘要 ( 7035 )

Bipyridylporphyrin derivatives possessing a porphyrin moiety as the electron donor and bipyridyl moiety as the electron-acceptor were designed and synthesized for dye-sensitized solar cells (DSSCs). The photophysical and electrochemical properties were investigated by absorption spectrometry and cyclic voltammetry. Density functional theory (DFT) was employed to study electron distribution. From the photovoltaic performance measurements, a maximum conversion efficiency (η) of 0.38% was achieved based on the bipyridylporphyrin ruthenium dye A7(J_SC=1.33 mA/cm², V_OC=0.45 V, FF=0.64) under 1.5 irradiation (100 mW/cm²).

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Development of Cu foam-based Ni catalyst for solar thermal reforming of methane with carbon dioxide

Jianzhong Qi, Yanping Sun, Zongli Xie, Mike Collins, Hao Du, Tianying Xiong

2015, 21(6): 786-793. DOI: 10.1016/j.jechem.2015.10.001

摘要 ( 4601 )

Using solar energy to produce syngas via the endothermic reforming of methane has been extensively investigated at the laboratory-and pilot plant-scales as a promising method of storing solar energy. One of the challenges to scaling up this process in a tubular reformer is to improve the reactor's performance, which is limited by mass and heat transfer issues. High thermal conductivity Cu foam was therefore used as a substrate to improve the catalyst's thermal conductivity during solar reforming. We also developed a method to coat the foam with the catalytically active component NiMg₃AlO_x. The Cu foam-based NiMg₃AlO_x performs better than catalysts supported on SiSiC foam, which is currently used as a substrate for solar-reforming catalysts, at high gas hourly space velocity (≥ 400,000 mL/(g·h)) or at low reaction temperatures (≤ 720℃). The presence of a γ-Al₂O₃ intermediate layer improves the adhesion between the catalyst and substrate as well as the catalytic activity.

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