Edge-carboxylated graphene nanoplatelets as oxygen-rich metal-free cathodes for organic dye-sensitized solar cells

Edge-carboxylated graphene nanoplatelets (ECGnPs) were synthesized by the simple, efficient and eco-friendly ball-milling of graphite in the presence of dry ice and used as oxygen-rich metal-free counter electrodes (CEs) in organic dye-sensitized solar cells (DSSCs), for the first time. The resultant ECGnPs are soluble in many polar solvents including 2-propanol due to the polar nature of numerous carboxylic acids at edges, allowing an electrostatic spray (e-spray) to be deposited on fluorine-doped SnO2 (FTO)/glass substrates. The ECGnP-CE exhibited profound improvements in the electrochemical stability for the Co(bpy)3 2+/3+ redox couple compared to the platinum (Pt)-CE. The charge transfer resistance (RCT), related to the interface between an electrolyte and a CE, was significantly reduced to 0.87 ?? cm2, much lower than those of (Pt)-CE (2.19 ?? cm 2), PEDOT:PSS-CE (2.63 ?? cm2) and reduced graphene oxide (rGO)-CE (1.21 ?? cm2). The DSSC based on the JK-303-sensitizer and ECGnP-CE displayed a higher photovoltaic performance (FF, Jsc, and ??, 74.4%, 14.07 mA cm-2 and 9.31%) than those with the Pt-CE (71.6%, 13.69 mA cm-2 and 8.67%), PEDOT:PSS (68.7%, 13.68 mA cm-2 and 8.25%) and rGO-CE (72.9%, 13.88 mA cm-2 and 8.94%).close3

Correlating the photovoltaic performance of alumina modified dye-sensitized solar cells with the properties of metal-free organic sensitizers

Low photovoltage for metal-free organic dye-sensitized solar cells (DSSCs) has been restricting them surpassing the equivalent cells based on ruthenium complex sensitizers (typically N719). In this study, an alumina (Al O) layer was employed to cover on the titania (TiO ) surface before dye loading in order to improve the photovoltage of the organic dye based DSSCs. The open-circuit voltage (Voc) of the solar cell was found to increase by 0.02-0.06 V for a variety of organic sensitizers by the presence of the AlO overcoat, while the photocurrent (J) was observed highly dependent on the property of the sensitizer. Results show that for the sensitizers with a low Low-Unoccupied-Molecular-Orbital (LUMO) level or a large molecular size, the DSSC yielded a decreased J due to two factors, (i) an insufficient driving force for electron injection due to the upshift of the conduction band level of the TiO/AlO electrode, and (ii) a decrease of dye adsorption amount for the TiO/AlO electrode in comparison with the referenced TiO electrode because of the reduced pore size and porosity by AlO coating. However, for the sensitizers with a high (more negative) LUMO level and a small molecular size, the J of the DSSCs based on the TiO/AlO electrode was very close to that composed of only TiO electrode. Using such organic dyes sensitizing on the TiO/AlO electrode, over 8% in the efficiency of the DSSCs was facilely attained and particularly an efficiency of 8.72% was obtained for a cocktail solar cell with two organic dyes

Efficient Hole Transporting Materials with Two or Four N,N-Di(4-methoxyphenyl)aminophenyl Arms on an Ethene Unit for Perovskite Solar Cells

Novel steric bulky hole transporting materials (HTMs) with two or four N,N-di(4-methoxyphenyl)aminophenyl units have been synthesized. When the EtheneTTPA was used as a hole transporting material in perovskite solar cell, the power conversion efficiency afforded 12.77 % under AM 1.5 G illumination, which is comparable to the widely used spiro-OMeTAD based solar cell (13.28 %). © 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.FALS

Hole transporting and light absorbing material for solid state solar cells

The present invention relates to a compound of formula (I) based on quinozilino acridine and used as hole transporting and light absorbing material in a photovoltaic device, in particular in a solid state solar cell

Efficient star-shaped hole transporting materials with diphenylethenyl side arms for an efficient perovskite solar cell

Two symmetrical star-shaped hole transporting materials (HTMs), i.e. FA-MeOPh and TPA-MeOPh with a fused triphenylamine or triphenylamine core and diphenylethenyl side arms were synthesized. FA-MeOPh showed a strong molar absorption coefficient and a red-shifted absorption compared with TPA-MeOPh because of its planar configuration. The power conversion efficiency (PCE) of the perovskite solar cells based on FA-MeOPh and TPA-MeOPh is about 11.86% and 10.79%, in which the efficiency of former is comparable to that (12.75%) of spiro-OMeTAD based cell. The high photocurrent (18.39 mA cm(-2)) of FA-MeOPh based solar cell relative to TPA-MeOPh based one may be attributable to the enhanced absorption in the near-IR region for mp-TiO2/CH3NH3PbI3/HTM based cell. The high mobility and low series resistance of mp-TiO2/CH3NH3PbI3/FA-MeOPh based cell led to the high fill factor (0.698) of FA-MeOPh based solar cell relative to TPA-MeOPh based one (0.627). In addition, the FA-MeOPh based cell showed a relative stability under light soaking for 250 h. The high efficiency, relative stability, synthetically simple and inexpensive materials as the HTMs hold promise to replace the expensive spiro-OMeTAD

Direct Evidence of Förster Resonance Energy Transfer for the Enhanced Photocurrent Generation in Dye-Sensitized Solar Cell

We meticulously designed organic antenna for the ruthenium phthalocyanine. A significant enhance-ment of photocurrent in JK-107 is attributed to a Förster energy transfer and intramolecular electron transfer from the antenna to the acceptor RuPc3. We demonstrate the direct evidence of Förster energy transfer and electron transfer for the enhanced photocurrent generation using photoluminescence spectroscopy and transient absorption spectroscopy, respectively