Routes to copper zinc tin sulfide Cu2ZnSnS4 a potential material for solar cells

Power generation through photovoltaics (PV) has been growing at an average rate of 40% per year over the last decade; but has largely been fuelled by conventional Si-based technologies. Such cells involve expensive processing and many alternatives use either toxic, less-abundant and or expensive elements. Kesterite Cu(2)ZnSnS(4) (CZTS) has been identified as a solar energy material composed of both less toxic and more available elements. Power conversion efficiencies of 8.4% (vacuum processing) and 10.1% (non-vacuum processing) from cells constructed using CZTS have been achieved to date. In this article, we review various deposition methods for CZTS thin films and the synthesis of CZTS nanoparticles. Studies of direct relevance to solar cell applications are emphasised and characteristic properties are collated.     

Inverted polymer solar cells with a solution-processed zinc oxide thin film as an electron collection layer

A solution-processed zinc oxide (ZnO) thin film as an electron collection layer for polymer solar cells (PSCs) with an inverted device structure was investigated. Power conversion efficiencies (PCEs) of PSCs made with a blend of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) are 3.50% and 1.21% for PSCs with and without the ZnO thin film, respectively. Light intensity dependence of the photocurrent and the capacitance-voltage measurement demonstrate that the increased PCEs are due to the restriction of the strong bimolecular recombination in the interface when a thin ZnO layer is inserted between the polymer active layer and the ITO electrode. These results demonstrate that the ZnO thin film plays an important role in the performance of PSCs with an inverted device structure.     

多硫电解质对CdS薄膜电池光电性能影响研究

在CdS薄膜的光电化学电池中,多硫电解质起着促进电子传递,减少电子空穴复合几率,从而提高电池光电转换效率的作用;但多硫电解质又会阻碍CdS薄膜对光的吸收。本文通过对CdS纳米管薄膜电池在含硫量不同的电解质中光电性能的考察,证明了0.5 mol/L Na2S、0.5 mol/L NaOH和0.5 mol/L S的液态电解质成分组合为本实验中制得的CdS纳米管薄膜光电化学电池的最佳电解质。     

Nb2O5 as a new electron transport layer for double junction polymer solar cells

Nb(2)O(5) as a new electron transport layer (ETL) was used for double junction polymer solar cells. The Nb(2)O(5) ETL was prepared by spin coating a Nb(2)O(5) sol-gel solution onto the active layer of the optical front subcell. The double junction devices using Nb(2)O(5) ETL exhibit an open circuit voltage (V(oc)) of 1.30 V, which is close to the sum of the s of the individual subcells. The current density-voltage (J-V) simulation showed that the double junction device performance using Nb(2)O(5) as ETL could be significantly increased by reducing the series resistance (R(se)) and matching the current densities of the individual subcells.     

High-surface-area microporous carbon as the efficient photocathode of dye-sensitized solar cells

This paper reports on the application of cornstalks-derived high-surface-area microporous carbon (MC) as the efficient photocathode of dye-sensitized solar cells (DSCs). The photocathode, which contains MC active material, Vulcan XC–72 carbon black conductive agent, and TiO₂ binder, was obtained by a doctor blade method. Electronic impedance spectroscopy (EIS) of the MC film uniformly coated on fluorine doped SnO₂ (FTO) glass displayed a low charge-transfer resistance of 1.32 Ω cm². Cyclic voltammetry (CV) analysis of the as-prepared MC film exhibited excellent catalytic activity for I₃^?/I^? redox reactions. The DSCs assembled with the MC film photocathode presented a short-circuit photocurrent density (J_sc) of 14.8 mA cm^?2, an open-circuit photovoltage (V_oc) of 798 mV, and a fill factor (FF) of 62.3%, corresponding to an overall conversion efficiency of 7.36% under AM 1.5 irradiation (100 mW cm^?2), which is comparable to that of DSCs with Pt photocathode obtained by conventional thermal decomposition.     

Non-hydrolytic ester-elimination reaction and its application in solution-processed zinc tin oxide thin film transistors

Journal of Sol-Gel Science and Technology - Solution-processed oxide thin films have many attractive features for various electronic applications as like a next generation display and flexible...     

Modulating the n- and p-type photoelectrochemical behavior of zinc copper indium sulfide quantum dots by an electrochemical treatment

An oxidative stripping treatment triggers the transition from n- to p-type photoelectrochemical behavior of zinc copper indium sulfide quantum dot electrodes. These electrodes in contact with a polysulfide solution change from photoanodic to photocathodic behavior in a certain potential range upon electrochemical treatment.     

Facile electrochemical growth of nanostructured copper phthalocyanine thin film via simultaneous anodic oxidation of copper and dilithium phthalocyanine for photoelectrochemical hydrogen evolution

We present a novel electrochemical approach to grow copper phthalocyanine (CuPc) thin-film photoelectrodes through anodic oxidation of copper and dilithium phthalocyanine (Li₂Pc). This circumvents the challenges associated with the electrochemical processing of unsubstituted CuPc from solution. The potentiostatic co-electrooxidation reaction at the heterogeneous interface favors the growth of CuPc thin film. The surface morphology of thin film exhibits nanorod-like features. UV-Vis, grazing angle Fourier transform infrared (FTIR), and grazing angle X-ray diffraction patterns reveal that the nanocrystalline phase corresponds only to α-CuPc and no admixture of other polymorphs. Photocurrent measurement shows a stable photoresponse in neutral medium. The photoelectrochemical hydrogen evolution on p-type CuPc coated copper photocathode shows an enhanced activity over bare copper and indium tin oxide (ITO) electrodeposited with CuPc and monolithium phthalocyanine radical (LiPc) thin films.     

Bismuth sulfide nanoflakes and nanorods as high performance photodetectors and photoelectrochemical cells

Flake-like and rod-like bismuth sulfide nanostructures were synthesized via a facile polyol refluxing process. The rigid photodetectors based on both nanomaterials have the features of linear photocurrent characteristics and good sensitivity. Especially, the rigid bismuth sulfide nanoflakes photodetector has fast response time of 0.5 s and recovery time of 0.7 s. The flexible photodetectors were then fabricated on PET substrate, and this caused both the response time and the recovery time to increase by a factor of ∼2.5. Moreover, the photoelectrochemical (PEC) devices exhibited photosensitivity with the features of rapid response and recovery time, high on/off ratio and stable switching cycle performance. Our results imply that the two types of bismuth sulfide nanomaterials are prospective candidates for next generation photodetectors and optoelectronic switches.     

High molar extinction coefficient heteroleptic ruthenium complexes for thin film dye-sensitized solar cells

Two novel heteroleptic sensitizers, Ru((4,4-dicarboxylic acid-2,2'-bipyridine)(4,4'-bis(p-hexyloxystyryl)-2,2-bipyridine)(NCS)2 and Ru((4,4-dicarboxylic acid-2,2'-bipyridine)(4,4'-bis(p-methoxystyryl)-2,2'-bipyridine) (NCS)2, coded as K-19 and K-73, respectively, have been synthesized and characterized by 1H NMR, FTIR, UV-vis absorption, and emission spectroscopy and excited-state lifetime and spectroelectrochemical measurements. The introduction of the alkoxystyryl group extends the conjugation of the bipyridine donor ligand increasing markedly their molar extinction coefficient and solar light harvesting capacity. The dynamics of photoinduced charge separation following electronic excitation of the K-19 dye was scrutinized by time-resolved laser spectroscopy. The electron transfer from K-19 to the conduction band of TiO2 is completed within 20 fs while charge recombination has a half-life time of 800 s. The high extinction coefficients of these sensitizers enable realization of a new generation of a thin film dye sensitized solar cell (DSC) yielding high conversion efficiency at full sunlight even with viscous electrolytes based on ionic liquids or nonvolatile solvents. An unprecedented yield of over 9% was obtained under standard reporting conditions (simulated global air mass 1.5 sunlight at 1000 W/m2 intensity) when the K-73 sensitizer was combined with a nonvolatile "robust" electrolyte. The K-19 dye gave a conversion yield of 7.1% when used in conjunction with the binary ionic liquid electrolyte. These devices exhibit excellent stability under light soaking at 60 degrees C. The effect of the mesoscopic TiO2 film thickness on photovoltaic performance has been analyzed by electrochemical impedance spectroscopy (EIS).     

Economical and effective sulfide catalysts for dye-sensitized solar cells as counter electrodes

Molybdenum sulfide (MoS(2)) and tungsten sulfide (WS(2)) are proposed as counter electrode (CE) catalysts in a I(3)(-)/I(-) and T(2)/T(-) based dye-sensitized solar cells (DSCs) system. The I(3)(-)/I(-) based DSCs using MoS(2) and WS(2) CEs achieved power conversion efficiencies of 7.59% and 7.73%, respectively.     

CuWO4|MnWO4 heterojunction thin film with improved photoelectrochemical and photocatalytic properties using simulated solar irradiation

Journal of Solid State Electrochemistry - In this paper, we report the synthesis of CuWO4, MnWO4, and FTO|CuWO4|MnWO4 as type II heterojunction thin film prepared by the drop-casting method. These...     

Enhancement of thin film tin oxide negative electrodes for lithium batteries

Thin films of pure SnO₂, of the Sn/Li₂O layered structure, and of Sn/Li₂O were fabricated by sputtering method, while a `lithium-reacted tin oxide thin film' was assembled by the evaporation of lithium metal onto a SnO₂ thin film. Film structure and charge/discharge characteristics were compared. The lithium-reacted tin oxide thin film, the Sn/Li₂O layered structure, and the Sn/Li₂O co-sputtered thin films did not show any irreversible side reactions of forming Li₂O and metallic Sn near 0.8 V vs Li/Li⁺. The initial charge retention of the Sn/Li₂O layered structure and Sn/Li₂O co-sputtered thin films was about 50% and a similar value was found for the lithium-reacted tin oxide thin film (more than 60%). Sn/Li₂O layered structure and Sn/Li₂O co-sputtered thin films showed better cycling behavior over 500 cycles than the pure SnO₂ and lithium-reacted tin oxide thin film in the cut-off range from 1.2 to 0 V vs Li/Li⁺.