Search

Massive production of graphene is synthesized by a low-cost electro-chemically exfoliated approach and then incorporated with γ-alumina for developing a novel carbon composite ink, graphene/γ-alumina ink. It is coated onto the glass by spraying with an adiabatic closed system as the thermal and optical barriers for the energy efficient glass of the business buildings. The coating thickness of graphene/γ-alumina layer is around 2~3 μm. The temperature in an adiabatic closed system is measured with a heat source by lamp radiation. The temperature difference between inside and outside of the adiabatic closed system can achieve around 20 °C with the coating of 0.3 wt% of electro-chemically exfoliated graphene incorporated with 1 wt% of γ-alumina in N-Methyl-2-Pyrrolidone after thermal radiation test for 15 h. The transmittance is adjustable from 5.57%–81% at 550 nm wavelength, depending on the composition and content of graphene and γ-alumina. The coating of the carbon composite ink, electro-chemically exfoliated graphene with γ-alumina are also good absorbents for UV absorbance. • The liquid composite of electro-chemically exfoliated graphene incorporated with γ-alumina is massively produced. • This liquid composite, graphene/γ-alumina can be used for energy efficient glass by simple spray coating. • The coating thickness of graphene/γ-alumina layer is around 2~3 μm. • The temperature difference between inside and outside of the adiabatic closed system can achieve around 20 °C. • The transmittance is adjustable from 5.57%–81% at 550 nm wavelength. [ABSTRACT FROM AUTHOR]

Comprehensive studies were carried out to explore the roles of phenyl-C 61 -butyric acid methyl ester (PCBM) thin films in inverted-type CH 3 NH 3 PbI 3 (MAPbI 3 ) based photovoltaics, including the surface morphologies, transmittance spectra, photoluminescence spectra, X-ray diffraction (XRD) patterns, Raman scattering spectra and thin-film residual stress analysis. The reduction in the photoluminescence line width indicates that the crystallinity of the MAPbI 3 thin film can be increased by covering it with the PCBM thin film. The XRD patterns and Raman scattering spectra show a reduction in the compressive stress of MAPbI 3 thin film when covered by the PCBM thin film. In addition, it is noted that the residual stress at the contact interface between the hydrophilic MAPbI 3 and the hydrophobic PCBM can be ignored as confirmed by the results obtained with a home-made Twyman-Green interferometer. Consequently, the superior optoelectronic properties of the perovskite materials, as well as the use of a multifunctional fullerene-based thin film as the capping layer allow for the high-efficiency perovskite photovoltaics. [ABSTRACT FROM AUTHOR]

A series of alcohols (methanol, ethanol and isopropyl alcohol) were added to poly(3,4-ethylenedioxythiophene): (polystyrene sulfonate) (PEDOT: PSS) aqueous solutions in order to manipulate the molecular structure of the PEDOT chains in PEDOT: PSS hole transporting materials (HTMs) and thus to improve the power conversion efficiency of CH 3 NH 3 PbI 3 based solar cells. The structural and electronic characteristics of the resultant PEDOT: PSS HTMs were analyzed using atomic-force microscopy, contact angle measurement, Raman scattering spectrometry and photoelectron spectrometry. The properties of the PEDOT: PSS thin films could be controlled by tuning the viscosity of the PEDOT: PSS solutions. High viscosity PEDOT: PSS solutions resulted in linear structured PEDOT chains, which increased the work function of the PEDOT: PSS HTMs thereby improving the open-circuit voltage of the CH 3 NH 3 PbI 3 solar cells. The surface roughness and surface free energy of the PEDOT: PSS HTMs influence the structural properties of CH 3 NH 3 PbI 3 thin films, which determines the exciton dissociation at the CH 3 NH 3 PbI 3 /PEDOT: PSS interface (short-circuit current density) and the carrier recombination at the CH 3 NH 3 PbI 3 /[6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) interface (fill factor). In addition, it is predicted that the power conversion efficiency can be further improved by increasing the crystallinity of the CH 3 NH 3 PbI 3 thin film. [ABSTRACT FROM AUTHOR]

A series of nonpolar antisolvents (chlorobenzene, bromobenzene, iodobenzene and toluene) were used to assist in the formation of smooth and crystalline CH 3 NH 3 PbI 3 thin films by a one-step spin-coating method. The structural, optical and excitonic characteristics of the resultant CH 3 NH 3 PI 3 thin films were analyzed using an atomic-force microscope, X-ray diffractometer, absorbance spectrum, photoluminescence (PL) spectrum, time-resolved PL and temperature-dependent PL. The properties of the CH 3 NH 3 PbI 3 thin films are dependent on the relative polarity and boiling point of the nonpolar antisolvents used in the washing treatment process. The interplay between nucleation (relative polarity) and crystal growth (boiling point) during the formation of CH 3 NH 3 PbI 3 thin films influences the short-circuit current density (J SC ) and power conversion efficiency (PCE) of the corresponding solar cells. The experimental results demonstrate that iodobenzene can be substituted for toluene as a more efficient antisolvent in the washing treatment process during the fabrication of CH 3 NH 3 PbI 3 thin films. In addition, it is predicted that the J SC and PCE can be further improved by increasing the crystallinity of the CH 3 NH 3 PbI 3 thin film. [ABSTRACT FROM AUTHOR]

A comprehensive study was carried out to understand the influence of organic cations on high-performance CH 3 NH 3 PbI 3 based photovoltaics. Scanning electron microscope, X-ray diffractometer, Hall measurement, absorbance spectrum, photoluminescence (PL) spectrum and nanosecond time-resolved PL measurements were used to explore the structural, electrical, optical and excitonic characteristics of CH 3 NH 3 PbI 3 thin films fabricated under different thermal annealing temperatures from 60 °C to 140 °C. The decrease in the open-circuit voltage ( V OC ) with an increase in the thermal annealing temperature can be explained as due to the reduced work function of the CH 3 NH 3 PbI 3 thin film. The short-circuit current density ( J SC ) of the CH 3 NH 3 PbI 3 based photovoltaics is dependent on the efficiencies of light absorption and carrier collection, which results in an optimized J SC when the thermal annealing temperature is 120 °C. The atomistic interaction between the organic cations and Pb–I framework strongly influences the absorbance of CH 3 NH 3 PbI 3 thin films, as confirmed by the libration of CH 3 NH 3 cations shown by Raman scattering spectroscopy. In addition, the experimental results indicate that the power conversion efficiency can be further improved when the absorption strength of the CH 3 NH 3 PbI 3 thin film and the energy-level alignment of each photovoltaic layer are simultaneously fulfilled. [ABSTRACT FROM AUTHOR]

A comprehensive study was carried out to understand the formation of a crystalline tri-iodide perovskite absorber (TPA) on top of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Scanning electron microscopy, two-dimensional X-ray diffraction and nanosecond time-resolved photoluminescence were used to explore the correlation between the surface morphology and the exciton lifetime in TPA fabricated with and without the in-situ toluene washing treatment. The toluene washing treatment decreases the crystallinity (exciton lifetime) of TPA and improves the TPA coverage on the non-crystalline PEDOT:PSS surface. The high average power conversion efficiency (PCE) of 10.61% achieved can be explained as due to the efficient exciton dissociation at the interface between the TPA and the PEDOT:PSS. The experimental results show that the PCE can be further improved when the crystallinity of TPA and the TPA coverage on PEDOT:PSS are simultaneously optimized. [ABSTRACT FROM AUTHOR]

Abstract: Hybrid optical layers of PMMA containing different concentrations of CdSe/ZnS core/shell semiconductor quantum dots were fabricated. Their absorption and luminescence showing quantum confinement effects are given. A frequency down-conversion is then obtained. The external quantum efficiency measurement performed on silicon solar cell with and without the down-conversion layers shows that the luminescence induces new charge generation. In addition, Finite Difference Time Domain (FDTD) simulation of organic solar cell shows that, added to the frequency conversion effect, one can expect to have an increase in light confinement when quantum dots are embedded in the active layer. [Copyright &y& Elsevier]

Transmittance spectra, atomic-force microscopic images, energy-dispersive X-ray spectra and droplet contact angle images show that a facile wet etching process can be used to manipulate the thickness, surface roughness, surface chemical composition and surface wettability of the indium-tin oxide (ITO) thin films, which influences the molecular packing structure of the P3CT-Na thin films and thereby dominating the crystal quality of the CH 3 NH 3 PbI 3 (MAPbI 3) thin films. The power conversion efficiency (PCE) of the P3CT-Na based MAPbI 3 solar cells can be improved from 17.02% to 19.35% by increasing the Sn/In concentration ratio of the ITO thin films from 0.36 to 0.47 with a facile wet etching process at a constant temperature of 40 °C. It is noted that the PCE of the optimal solar cell decreases slowly toward a stable PCE of 16% for more than 60 days under moderate environment conditions (55 ± 10 RH%). • Surface properties of the ITO/glass substrates can be varied by the wet etching process. • The contact quality at the P3CT-Na/ITO interface can be improved. • The contact quality at the MAPbI3/P3CT-Na interface can be improved. • After 60 days, the PCE slowly decreased from 19.35% to 16.03%. [ABSTRACT FROM AUTHOR]