Conjugated polymer‐functionalized graphite oxide sheets thin films for enhanced photovoltaic properties of polymer solar cells

In this study, the maleimide‐thiophene copolymer‐functionalized graphite oxide sheets (PTM21‐GOS) and carbon nanotubes (PTM21‐CNT) were developed for polymer solar cell (PSC) applications. The grafting of PTM21‐OH onto the CNT and GO sheets was confirmed using FTIR spectroscopy. PTM21‐CNT and PTM21‐GOS exhibited excellent dispersal behavior in organic solvents. Better thermal stability was observed for PTM21‐CNT and PTM21‐GOS as compared with that for PTM21‐OH. In addition, the optical band gaps of PTM21‐GOS and PTM21‐CNT were lower than that of PTM21‐OH. We incorporated PTM21‐GOS and PTM21‐CNT individually into poly(3‐hexylthiophene) (P3HT)/[6,6]‐phenyl‐C₆₁‐butyric acid methyl ester (PCBM) blends for use as photoconversion layers of PSCs. Good distributional homogeneity was observed for PTM21‐GOS or PTM21‐CNT in the P3HT/PCBM blend film. The UV–vis absorption peaks of the blend films red‐shifted slightly upon increasing the content of PTM21‐GOS or PTM21‐CNT. The band gap energies and LUMO/HOMO energy levels of the P3HT/PTM21‐GOS and P3HT/PTM21‐CNT blend films were slightly lower than those of the P3HT film. The conjugated polymer‐functionalized PTM21‐GOS and PTM21‐CNT behaved as efficient electron acceptors and as charge‐transport assisters when incorporated into the photoactive layers of the PSCs. PV performance of the PSCs was enhanced after incorporating PTM21‐GOS or PTM21‐CNT in the P3HT/PCBM blend. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013     

Temperature-dependence of electric and photovoltaic properties of HgTe thin film

The I–V characteristics of an illuminated thin film of HgTe and of a dark sample were recorded. The high values of the photoelectric current of the illuminated sample as the distance decreased may be due to the impurity conductivity, that can be higher than the band conduction predominating at higher incident energy. In the dark, the impurity conductivity is always low compared to the band conductivity occurring at the higher incident energy of mercury light. The low mobility and the increase of the activation energy with increasing temperature suggest that more than one conduction mechanism is involved. The high density of acceptor centres in the thin layer of HgTe may affect the conduction current in certain temperature ranges.The dielectric constant of the HgTe thin film was measured at different temperatures. The increase of the dielectric constant might be due to point defects which are Hg-vacancy or Te-interstitial acceptors. HgTe has an excess of Te and the net hole concentration (p-n) can be altered by increasing the ionized acceptor defects which migrate through the cubic crystallites to accumulate at the electrodes, giving rise to the dielectric constant.

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Zusammenfassung Die Strom-Spannungs-Charakteristik eines dünnen HgTe-Filmes wurde bei Einfall von Licht und im Dunklen registriert. Die hohen Werte des photoelektrischen Stromes der beleuchteten Probe bei abnehmenden Abstand können der durch Verunreinigungen bedingten Leitfähigkeit zugeschrieben werden, die bei größerer Einfallsenergie größer als die Bandleitfähigkeit sein kann. Im Dunklen ist die durch Verunreinigungen bedingte Leitfähigkeit immer gering im Vergleich zur Bandleitfähigkeit beim Einfall größerer Energiemengen von Hg-Licht. Die geringe Mobilität und der Anstieg der Aktivierungsenergie mit ansteigender Temperatur deuten darauf hin, daß am Vorgang mehr als nur ein Leitungsmechanismus beteiligt ist. Die hohe Dichte der Akzeptorzentren in der dünnen HgTe-Schicht beeinflußt den Leitfähigkeitsstrom in bestimmten Temperaturbereichen. Die dielektrische Konstante des dünnen HgTe-Filmes wurde bei verschiedenen Temperaturen gemessen. Der Anstieg der dielektrischen Konstante kann punktförmigen Gitterfehlern, nämlich Hg-Vakanzen oder interstitionellen Te-Akzeptoren zugeschrieben werden. HgTe hat einen Te-Überschuß, und die Gitterfehlstellenkonzentration kann durch Vermehrung der ionisierten Akzeptordefekte verändert werden, die durch die kubischen Kristallite migrieren, sich an den Elektroden anhäufen und so das dielektrische Verhalten bewirken.

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(I–V) HgTe. , , , . , . , . HgTe . HgTe. , Hg- - . (-) , , , .

     

CdS和CdSe薄膜的制备及其光电化学性质

本文采用简易的化学水浴沉积法和自牺牲模板法制备CdS、CdSe薄膜,对两种薄膜进行了XRD表征,比较了两种薄膜的紫外吸收光谱并研究了CdS、CdSe薄膜作为太阳能电池中的光阳极时所产生的光电流和光电压,对两种薄膜的电化学性能进行了比较.     

A highly efficient electric additive for enhancing photovoltaic performance of dye-sensitized solar cells

N-cetylpyridinium iodide (N-CPI) as a new electric additive for enhancing photovoltaic performance of the dye-sensitized solar cell (DSSC) was studied. It showed high efficiency for enhancing both the open-circuit voltage and the short-circuit current density of DSSC when the suitable amount of N-CPI as 0.02 M was added in liquid electrolyte. The energy conversion efficiency of DSSC increased from 4.429% to 6.535%, with 47.55% enhancement. Therefore, it is a highly efficient electric additive for DSSC. The intrinsic reason is owing to the special molecular structure of N-CPI, which contains two different polarity groups. As a surfactant, N-CPI could form ordered arrangement in liquid electrolyte, which affects the diffusing ability and the redox reaction of I^?/I ₃ ^? , and further affects the photovoltaic performance of DSSC.     

一种高效染料敏化太阳电池电解质添加剂

报道了一种新型染料敏化太阳电池电解质添加剂——N-十六烷基吡啶碘(N-CPI).往电解质中添加0.02MN-CPI,能同时提高染料敏化太阳电池(DSSC)的短路电流和开路电压,光电转换效率也由4.429%提高到6.535%,增幅高达47.55%,由此可见,N-CPI是一种高效电解质添加剂.N-CPI这种功能来源于其双极性基团的特殊分子结构,这种结构使N-CPI在电解质中如表面活性剂那样形成有序分布,影响I-/I3-的扩散和氧化还原性能,进而影响DSSC的光电性能.     

Effect of coadsorbent properties on the photovoltaic performance of dye-sensitized solar cells

Stearic acid as a coadsorbent, which has a low dipole moment and high solubility, retarded the rate of dye adsorption during the competitive anchoring process on the TiO(2) layer in dye-sensitized solar cells (DSCs), thereby increasing the content of strongly bound dye on the TiO(2) surface. This resulted in an approximately 25% improvement in both J(SC) and the power conversion efficiency of the DSCs, even for much lower dye coverage.     

Influence of highly efficient PbS counter electrode on photovoltaic performance of CdSe quantum dots-sensitized solar cells

PbS electrode with high catalytic activity to S_n ^2? reduction certificated by the measurements of electrochemical impedance spectroscopy and cyclic voltammetry was prepared by a simple method. The high catalytic activity makes it be a low-cost alternative counter electrode to platinum (Pt) to be used in quantum dots-sensitized solar cells (QDSSCs) based on polysulfide electrolyte. The photovoltaic performance enhancement of the quantum dots (QDs)-sensitized semiconductor thin films due to the PbS counter electrode was evaluated by fabricating QDSSCs based on CdSe QDs-sensitized ZnO (SnO₂) thin film. CdSe QDs-sensitized ZnO thin film has the lower internal total series resistance and electron transmission time, the higher electron lifetime and electron collection efficiency than the CdSe QDs-sensitized SnO₂ thin film. Replacing the Pt counter electrode with the PbS counter electrode leads to more improvement on the short circuit photocurrent density for QDSSC based on the ZnO thin film than the SnO₂ thin film. Therefore, the process to limit the photovoltaic performance of CdSe QDs-sensitized solar cell and the possible way to improve the photovoltaic performance were analyzed.     

Systematic study on structural phase behavior of CdSe thin films

Cadmium selenide (CdSe) thin films were chemically deposited at room temperature, from aqueous ammoniacal solution using Cd(CH(3)COO)(2) as Cd2+ and Na(2)SeSO(3) as Se2- ion sources. The as-deposited films were uniform, well adherent to the glass substrate, specularly reflective, and red-orange in color. The as-deposited CdSe layers grew with nanocrystalline sphalerite cubic structure along with the amorphous phase present in it, with optical band gap E(g) = 2.3 eV. The films were annealed in air atmosphere for 4 h at different temperatures and characterized for compositional, structural, morphological, and optical properties. XRD and SEM studies clearly revealed the systematic phase transformation of CdSe films from metastable nanocrystalline cubic (zinc blende type) to a mixture of cubic and hexagonal (wurtzite type), and finally into stable hexagonal through different intermediate phases with an improvement in the crystal quality. The films showed a red shift in their optical spectra after annealing.     

Bismuth iron tungstate pyrochlore thin films for photovoltaic applications

Thin films based on the ternary complex oxide Bi_0.50Fe_0.4WO_q with a cubic pyrochlore structure were obtained and used for the first time as electron-transport layers in perovskite solar cells. The measured power conversion efficiency was ～ 4 rel% higher than that of state-of-the-art TiO₂-based perovskite solar cells.     

Conjugated polymer-functionalized carbon nanotubes enhance the photovoltaic properties of polymer solar cells

In this study, we fabricated a series of polymer solar cells (PSCs) incorporating blends of the maleimide?Cthiophene copolymer PTM10, multi-walled carbon nanotubes (MWCNTs) functionalized with the 2-hydroxyethyl?Cpresenting maleimide?Cthiophene copolymer PTM21-OH (PTM21-CNT), and the fullerene derivative [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) in various weight ratios. PTM21-CNT behaved as an efficient compatibilizer for PTM10 and PCBM and as a charge transport assister when incorporated in the photoactive layers of the PSCs. The energy levels of the lowest unoccupied molecular orbitals and highest occupied molecular orbitals in thin films of PTM10/PTM21-CNT/PCBM blends decreased upon increasing the PTM21-CNT content. The photovoltaic performance of PSCs incorporating the PTM10/PTM21-CNT/PCBM blends increased upon increasing the PTM21-CNT content, presumably because of the high charge-transporting capacity of the MWCNTs. The highest short-circuit current density and photo-energy conversion efficiency were enhanced by approximately 26% and 27%, respectively, relative to those of the PSC without the incorporation PTM21-CNT.     

Growth and morphological studies of NiO/CuO/ZnO based nanostructured thin films for photovoltaic applications

At present, inorganic semiconducting materials are the most economical and viable source for the renewable energy industry. The present work deals with the morphological and optical characterization of copper oxide (CuO) and zinc oxide (ZnO) thin films fabricated by layer by layer deposition on nickel oxide (NiO) coated indium tin oxide (ITO) glass by solution processing methods, mainly chemical bath deposition (CBD) and hydrothermal deposition (HTD) processes at room temperature. As a whole, the above inorganic composite materials (NiO/CuO/ZnO) can be applied in photovoltaic cells. An attempt has been made to study structural, morphological and absorption characteristics of NiO/CuO/ZnO heterojunction using state of the art techniques like X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV spectroscopy. The energy band gaps of CuO and ZnO have also been calculated and discussed based on the UV spectroscopy measurements.     

Plasma processed carbon thin films applied to dye-sensitized solar cells

Plasma-treated carbon thin films are investigated as counter electrodes for dye-sensitized solar cells. The films were grown onto fluorine-doped tin oxide (FTO) substrates by magnetron sputtering using pure graphite target and argon atmosphere and subsequently annealed at 600 °C for 30 min in vacuum. These films were then submitted to a plasma texturing process in a reactive ion etching reactor using three different gas combinations: sulfur hexafluoride/argon (SF₆ + Ar), sulfur hexafluoride/hydrogen (SF₆ + H₂), and sulfur hexafluoride/oxygen (SF₆ + O₂). The morphology and structure of the obtained films were characterized by scanning electron microscopy and Raman spectroscopy. Cyclic voltammetry technique allowed accessing the improvements in their catalytic properties, while the photocurrent-voltage curves under simulated solar illumination AM 1.5G (100 mW/cm²) evaluated the performance of the respective assembled solar cells. The results show that photovoltaic performance is significantly affected by the different plasma texturing conditions used. The carbon counter electrode obtained after SF₆ + O₂ plasma texturing achieved the best power conversion efficiency of 2.23%, which is comparable to the 2.31% obtained using the commercial platinum counter electrode.

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Graphical abstract Reactive Ion Etching reactor for plasma texturing process of carbon thin films

     

Electrochemical texturing of Al-doped ZnO thin films for photovoltaic applications

The processes during chemical and electrochemical etching of Al-doped ZnO are investigated utilizing a scanning flow cell setup with online detection of dissolved Zn ions. The rate of chemical dissolution was found to be a linear function of buffer and proton concentration in near neutral pH solutions according to a transport limited reaction. In contrast, electrochemical etching is limited by the kinetics of the reaction and increases linearly with the imposed current density. Due to this fundamental difference, the dissolution of Zn can be either uniform over the whole surface or highly localized at active sites like grain boundaries. A combined approach of chemical etching and the well-controllable galvanostatic dissolution thus allows a fine adjustment of the ZnO:Al surface texture for applications in silicon thin film photovoltaic cells in order to improve their overall energy conversion efficiency.     

Chemical surface deposition and growth rate of thin CdSe films

Chemical surface deposition of thin CdSe films was studied. The conditions for preparing thin films were examined, the degrees of Cd conversion in the starting compounds were determined, and the film thicknesses were measured.     

Strategies and methods for fabricating high quality metal halide perovskite thin films for solar cells

With the development of human society,the problems of environmental deterioration and energy short-age have become increasingly prominent.In order to solve thes...     

Effect of additives on the photovoltaic properties of organic solar cells based on triphenylamine-containing amorphous molecules

Photovoltaic performance of the organic solar cells(OSCs)based on 2-((5′-(4-((4-((E)-2-(5′-(2,2-dicyanovinyl)-3′,4-dihexyl-2,2′-bithiophen-5-yl)vinyl)phenyl)(phenyl)amino)styryl)-4,4′-dihexyl-2,2′-bithiophen-5-yl)methylene)malononitrile(L(TPAbTV-DCN))as donor and PC70BM as acceptor was optimized using 0.25 vol%high boiling point solvent additive of1-chloronaphthalene(CN),1,6-hexanedithiol(HDT),or 1,8-diodooctane(DIO).The optimized OSC based on L(TPA-bTVDCN)–PC70BM(1:2,w/w)with 0.25 vol%CN exhibits an enhanced power conversion efficiency(PCE)of 2.61%,with Voc of0.87 V,Jsc of 6.95 mA/cm2,and FF of 43.2%,under the illumination of 100 mW/cm2 AM 1.5 G simulated solar light,whereas the PCE of the OSC based on the same active layer without additive is only 1.79%.The effect of the additive on absorption spectra and the atomic force microscopy images of L(TPA-bTV-DCN)–PC70BM blend films were further investigated.The improved efficiency of the device could be ascribed to the enhanced absorption and optimized domain size in the L(TPA-bTV-DCN)–PC70BM blend film.     

Photoelectrochemical solar cell properties of heteropolytungstic acid-incorporated TiO2 nanodisc thin films

Thin film of heteropolytungstic acid (HPA)-incorporated TiO₂ nanodisc was fabricated, and its photovoltaic performances were observed as a function of irradiation wavelength from 400 nm to 750 nm. Its incident photon-to-current efficiency (IPCE) was determined to be 18.6% around 500 nm, with energy conversion efficiency of 6.9%, which were observed to be further enhanced to 23% and 9%, respectively, by adsorption of ruthenium or porphyrin dyes. Complementary electron transports from both HPA and dyes to TiO₂ nanodisc seems to avoid most of the backward electron or hole transfer reactions to enhance the photoelectrochemical efficiencies of dye-sensitized solar cells.     

Organic photovoltaic materials and thin-film solar cells

Organic photovoltaic materials are of interest for their future applications in solar cells. Compared to inorganic or dye-sensitized solar cells, organic photovoltaic (OPV) cells offer a huge potential for low-cost large-area solar cells because of their low material consumption per area and easy processing. In the last few years, there have seen an unprecedented growth of interest in OPVs with power conversion efficiency of over 5% attainable. However, OPV’s performance is limited by the narrow light absorption, poor charge carries mobility, and low stability of organic materials, all of which confine its large-scale commercial applications. This review will develop a discussion on the OPV device configuration and operational mechanism after an introduction of the general features of OPV materials. Subsequently, the typical progresses in materials development and performance evolution in recent years will be summarized. The future challenges and prospects faced by organic photovoltaics will be discussed. Finally, the innovative strategy on research of molecular design and device optimization will be suggested with the aim for practical application.     

Novel alkoxyanthracene donor and benzothiadiazole acceptor for organic thin film transistor and bulk heterojunction organic photovoltaic cells

Novel alkoxy anthracene (ODA)‐based polymeric semiconductors were designed for polymer solar cell applications. Alkoxyanthracene, which contains many π electrons and electron donating group, was easily synthesized. The copolymers, poly(alkoxy anthracene‐alt‐thiophene benzothiadiazole thiophene) poly(ODA‐TBT) and poly(alkoxy anthracene‐alt‐benzothiadiazole) poly(ODA‐BT), have been obtained by Suzuki coupling polymerization. Both polymers have ODA unit as a donor and benzothiadiazole as an acceptor. ODA‐TBT has thiophene linkages between ODA and benzothiadiazole. The optical, thermal, and electrochemical properties have been investigated by UV–visible absorption, thermal gravimetric analysis, differential scanning calorimetry, and CV. Organic thin‐film transistor using polymers showed that the hole mobility of poly(ODA‐alt‐TBT) was around 3.6 × 10^?3 cm²/Vs with on/off ratio of 9.91 × 10⁵ while that of poly(ODA‐alt‐BT) was around 1.21 × 10^?2 cm²/Vs with on/off ratio of 2.64 × 10⁶. Organic photovoltaic performance based on polymers were evaluated with a configuration of ITO/PEDOT:PSS/active layer/LiF/Al. Poly(ODA‐TBT) exhibits a short circuit current (J_sc) of 3.9 mA/cm² and power conversion efficiency (PCE) of 1.4%, and poly(ODA‐BT) exhibits the J_sc of 6.4 mA/cm² and PCE of 2.2%. The better device performance of poly(ODA‐BT) is attributed to its charge transfer ability and enhanced mobility and crystallinity although poly(ODA‐BT) does not have extended π‐conjugation due to twisted structure compared with poly(ODA‐TBT). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1306–1314     

Spectral broadening in quantum dots-sensitized photoelectrochemical solar cells based on CdSe and Mg-doped CdSe nanocrystals

In order to absorb a broad spectrum in visible region, a co-sensitized TiO₂ electrode was prepared by CdSe and Mg-doped CdSe quantum dots (Q dots). The power conversion efficiency of the co-sensitized Q dots photoelectrochemical solar cells (PECs) showed 1.03% under air mass 1.5 condition (I = 100 mW/cm²), which is higher than that of individual Q dots-sensitized PECs. The incident-photon-to-current conversion efficiency of the co-sensitized PECs showed absorption peaks at 541 and 578 nm corresponding to the two Q dots and displayed a broad spectral response over the entire visible spectrum in the 500–600 nm wavelength domains.