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To extend the spectral response region of squaraine dye (SQ)-sensitized solar cell, eosin Y (EY) is encapsulated in the SQ-sensitized nanocrystalline thin film. EY is first adsorbed on nanocrystalline TiO thin film (n-TiO), then a thin layer of EY contained ZnO (EY-ZnO) is electrodeposited, and SQ dye is finally sensitized to form two dye-sensitized nanocrystalline thin film with a structure of n-TiO/EY/EY-ZnO/SQ. There is a perfect spectral overlap between the emission of EY and the absorption of SQ; EY as an energy donor simultaneously transfers both electron and hole to the energy acceptor SQ according to the Förster resonance energy transfer (FRET) process. EY shifts the spectral response edge of SQ-sensitized solar cell toward blue from 550 to 450 nm through the FRET process in this new structure. Two dye-sensitized nanocrystalline thin film demonstrates a significant enhancement in light harvesting and photocurrent generation due to the FRET process. The thickness of the EY-ZnO thin layer and spectral overlap between emission of donor dye and absorption of acceptor dye are two important factors that affect the FRET process between EY and SQ in the structure of n-TiO/EY/EY-ZnO/SQ. [ABSTRACT FROM AUTHOR]

Abstract: This work entails a method to improve the performance of dye-sensitized nanocrystalline TiO2 solar cells by adding surface passivating elements to the electrolyte. The presence of either CO2, Li2CO3 or K2CO3 in electrolyte increases both the photocurrent and the photovoltage, resulting in higher overall conversion efficiency of these solar cells. The additives are used to form a passivation layer of lithium carbonate on the dye free surface of the TiO2 nanoparticles and the conductive substrate. This layer suppresses the rate of the main recombination reaction between the photoinjected electrons and the oxidized ions in the electrolyte solution. While blocking part of the recombination, the lithium carbonate layer allows motion of the Li+ ions towards the TiO2 surface for charge screening. Consequently using this simple treatment, the conversion efficiency of dye-sensitized solar cell most improved by 17.2% (from 6.4% to 7.5%). [Copyright &y& Elsevier]

Abstract: 4-Ethoxy-2-methylpyridine (EOP), as an electrolyte additive, was added into electrolyte of dye-sensitized solar cell, and its effect on the performance of solar cells and mechanism were studied by electrochemical and spectral measurements. With increasing in EOP concentrations, the flatband potential of TiO2 electrode shifted negatively and the rate of interfacial recombination at the TiO2 electrode/dye/electrolyte interfaces was improved. The net effect of EOP was to improve the open-circuit photovoltage, indicating that the negative shift of conduction band of TiO2 was the predominated factor on determining the open-circuit photovoltage. The decline of short-circuit current of solar cell was ascribed to the slow dye regeneration and the low catalytic activity of counter electrode on triiodide reduction due to addition of EOP. [Copyright &y& Elsevier]

Compression and incorporated graphene significantly improve light transmittances and charge transport properties of an opaque and poor internal-connected mesoporous photoanode, as well as improve the PCE of the corresponding device. Semi-transparent TiO 2 /graphene photoanodes are prepared at room temperature via an electrophoretic deposition method followed by compression and applied in dye-sensitized solar cells (DSSCs). Compression enhances the power conversion efficiency (PCE) of a DSSC, which constitutes up 18.4 times improvement compared to the uncompressed device. Incorporating graphene into the compressed film further improves the PCE by 28.8%. Simultaneously, compressing and graphene incorporating can greatly increase the film's transmittance at long wavelengths, benefiting to the use of DSSCs as front unit in tandem solar cells. Scanning electron microscopy, porosity measurements, electrochemical impedance spectroscopy and open circuit voltage decay are performed to investigate the mechanisms. It is demonstrated that compressing a film can reduce the porosity and improve the inter-particle connections, which accounts for the increased light transmittance and enhanced PCE. The incorporated graphene can provide extra charge carrier pathway due to its excellent charge transport properties, as well as protect TiO 2 nanostructure by preventing film cracking upon pressing due to its good flexibility, thus increases PCE to 6.75%, which, to our best knowledge, is the highest value among DSSCs with room-temperature prepared photoanodes. [ABSTRACT FROM AUTHOR]

Methylamine lead iodide (CH 3 NH 3 PbI 3) perovskite thin film solar cell has attracted much attention due to its low cost and high photoelectric conversion efficiency. Preparation of high quality perovskite thin film is the key to obtain high conversion efficiency of solar cells. Here, the pinhole-free CH 3 NH 3 PbI 3 layer with high coverage and smooth surface is prepared by the one-step solution method in air with ethylacetate as anti-solvent on an electron transport hybrid layer of TiO 2 nanoparticles coated porous carbon. The effect of ethylacetate as anti-solvent on the quality of perovskite thin film is studied in detail by comparing with chlorobenzene and ethylether. The high saturation and humidity resistance of ethylacetate in air control the nucleation and growing kinetics of perovskite crystals during the spin coating process, which facilitates the formation of uniform pinhole-free perovskite thin films. The perovskite solar cell based on the prepared high quality thin film achieves the highest conversion efficiency of 17.41% in ambient air with a relative humidity of 35%, which is superior to the perovskite thin films prepared with chlorobenzene and ethylether (conversion efficiency of 10.80% and 10.20%). The higher light-to-electric conversion efficiency is due to high coverage of the pinhole-free perovskite thin film and good contact with the electron transport layer and the hole transport layer. The high quality CH 3 NH 3 PbI 3 layer is prepared by the one-step solution method in air with ethylacetate as anti-solvent on an electron transport hybrid layer of TiO 2 nanoparticles coated porous carbon. The perovskite solar cell based on the prepared high quality thin film achieves the highest conversion efficiency of 17.41% in ambient air, which is due to high coverage of the pinhole-free perovskite thin film and good contact with the electron transport layer. Image 1 • Ethylacetate was used as anti-solvent to deposit high quality perovskite layer in air. • The saturation and humidity resistance of ethylacetate change the crystal kinetics. • The smooth pinhole-free perovskite layer with high coverage was prepared in air. • Perovskite solar cell based on the prepared film achieves the conversion efficiency of 17.41%. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Hydroxypropyl cellulose is added into the precursor solution to deposit big size CZTS paritcles. • Addition of hydroxypropyl cellulose obviously improved the surface morphologies of CZTS film. • The conversion efficiency of CZTS solar cell is enhanced by 89% due to addition of cellulose. Abstract Hydroxypropyl cellulose is added into the precursor solution to deposit Cu 2 ZnSnS 4 (CZTS) thin film for superstrate solar cell. The crystallinity and morphologies of CZTS thin films can be manipulated by adding a small amount of hydroxypropyl cellulose. With addition of 1.0 wt% hydroxypropyl cellulose, the crystallinity and grain size of CZTS are obviously improved, and the light-to-electric conversion efficiency of CZTS thin film solar cell is enhanced from 2.07% to 3.92%. The photoelectric performance enhancement mechanism is analyzed by the measurements of electrochemical impedance spectroscopy and intensity modulating photoelectrochemical spectroscopy of CZTS thin film solar cells and certificated to be formation of the bigger CZTS grains due to addition of hydroxypropyl cellulose, which reduces the boundary defects and makes the film surface be more continuous. These results suggest that addition of hydroxypropyl cellulose into the precursor solution is an effective way to obtain high performance CZTS thin film solar cells. [ABSTRACT FROM AUTHOR]

BaTiO 3 is used to fabricate the electron transport layer of perovskite solar cells due to its spontaneous polarization. Li+ ions were doped into BaTiO 3 by the hydrothermal synthesis to increase the spontaneous polarization. The particle size of the as-prepared BaTiO 3 nanoparticles becomes smaller and more uniform for doping of Li+ ions with a molar ratio of 1.0 during the synthesis processes. The absorption edge shifts towards the short wavelength with the increase in the doping amount. Further, TiO 2 nanocrystalline thin film was deposited on the Li-doped BaTiO 3 thin film, the double layer was used as an electron transport layer of perovskite solar cell to indirectly demonstrate the effect of doping on the spontaneous polarization of BaTiO 3. The perovskite solar cell based on BaTiO 3 with 1.0 doping molar ratio of Li+ ions shows the highest light-to-electric conversion efficiency of 14.3% accompanying with the highest short-circuit photocurrent density. The measurements of impedance spectra and intensity modulating photocurrent spectra indicate that the photocurrent enhancement of perovskite solar cells is attributed to the spontaneous polarization enhancement of Li-doped BaTiO 3 thin films. The enhanced internal electric field in the BaTiO 3 thin layer accelerates the photogenerated electron transport in the electron transport layer of perovskite solar cell. Image 1 • The Li+ doping affects spontaneous polarization on BaTiO 3. • The spontaneous polarization in Li-doped BaTiO 3 promotes the electron transport. • Li-doped BaTiO 3 in electron transport layer improves performance of perovskite solar cell. [ABSTRACT FROM AUTHOR]