Quang-Duy Dao

Alkyl Substituent Length Dependence of Octaalkylphthalocyanine Bulk Heterojunction Solar Cells

Alkyl substituent length dependences of photovoltaic performance of bulk-heterojunction (BHJ) organic solar cells (OSCs) utilizing 1,4,8,11,15,18,22,25-octaalkylphthalocyanine (CnPcH2) mixed in [6,6]-phenyl C71 butyric acid methyl ester have been studied. By shortening the alkyl substituents, stacking of the discotic CnPcH2 columns is probably changed from 2D rectangular lattices to pseudohexagonal structures, and Davydov splitting at the Q-band of CnPcH2 absorbance spectra decreases, which results in the higher hole mobility and the deeper highest occupied molecular orbital energy levels. As a result, the power conversion efficiencies of CnPcH2-based BHJ OSCs are improved from 0.3 to 3.7% by changing the alky substituent length.

Liquid crystalline and charge transport properties of novel non-peripherally octasubstituted perfluoroalkylated phthalocyanines

Two new perfluoroalkylated phthalocyanine derivatives were synthesised and characterised in order to investigate the effects of the fluorophobic/fluorophilic interactions on their mesophase and electronic properties. Both compounds exhibit columnar mesomorphism and the thermal stability of the columnar phase is enhanced by over 20 °C as the number of fluorinated carbons increases, probably due to the nano-segregation between the fluorinated and hydrocarbon moieties in the chains. Also a strong tendency towards spontaneous homeotropic alignment was observed. Time of Flight (ToF) measurements were carried out to reveal the mobility characteristics and the ambipolar mobility was measured in the order of 10−1 to 10−2 cm2 V−1 s−1 for the mesophases.

Annealing effect in bulk heterojunction organic solar cells utilizing liquid crystalline phthalocyanine

The effect of annealing on bulk heterojunction solar cells utilizing the liquid crystalline phthalocyanine, 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH2), fabricated using various solvents was studied. In the solar cells fabricated using chloroform, the power conversion efficiency was enhanced from 1.2 to 2.5% by thermal annealing at 75 ?C, near the glass-transition temperature of the bulk heterojunction film. We discuss the effects of annealing on the photovoltaic properties by considering the exciton dissociation and carrier transport efficiencies obtained from photoluminescence spectra, X-ray diffraction measurement, and atomic force microscope observation.

Blend ratio dependence of photovoltaic properties in octahexylphthalocyanine-based small molecule solar cell

A study on the blend ratio dependence of the photovoltaic properties in bulk heterojunction organic solar cells (OSCs) consisting of [6,6]-phenyl-C71 butyric acid methyl ester ([70]PCBM) and 1,4,8,11,15,18,22,25-octahexylphthalocyanine (C6PcH2) has been reported. With increasing the [70]PCBM volume fraction, the short-circuit current density was enhanced to be 10.6 mAcm−2 owing to the enlargement of the donor and acceptor interfacial areas. However, when the [70]PCBM volume fraction was higher than 33%, the fill factor was reduced owing to the deterioration of crystallization of discotic C6PcH2 molecules with hexagonal structures. The OSCs with the optimum blend ratio demonstrated a high power conversion efficiency of 3.9%.

Bulk-Heterojunction Thin-Film Solar Cells Utilizing Miscible Binary Donor Materials of Liquid Crystalline Phthalocyanine and its Analogue

Small-molecule bulk-heterojunction solar cells utilizing a binary-blended donor material composed of a liquid crystalline phthalocyanine and its analogue have been studied. The short-circuit current density (J sc) and power conversion efficiency (PCE) of the solar cells utilizing the blended donor material with an optimized blend ratio reached 11.6 mA/cm2 and 4.8%, respectively, which were superior to those of organic solar cells utilizing each donor material. The improvement of J sc and PCE has been discussed from the viewpoints of the crystal structure, optical and carrier transport properties of the blended donor material.

Improved synthesis of non-peripherally alkyl-substituted tetrabenzotriazaporphyrins

ABSTRACT Improvement of synthesis of non-peripherally alkyl-substituted macrocycle molecules, 1,4,8,11,15,18,22,25-octaalkyltetrabenzotriazaporphyrins (CnTBTAPH2) has been investigated. In the reaction from 3,6-dialkyl phthalonitrile to CnTBTAPH2, the yield has been markedly improved by replacing a conventional Grignard reagent with methyllithium. The modified procedure using a stable solvent was significantly effective for the scale-up of the reaction system as well as the yield enhancement.

Fabrication of tandem solar cells with all-solution processed multilayer structure using non-peripherally substituted octahexyl tetrabenzotriazaporphyrins

An effective way to improve the power conversion efficiencies (PCEs) of organic solar cells is to use a tandem structure, in which two organic solar cells with different absorption characteristics are linked to use a wider range of the solar spectrum. Herein, we report the fabrication of tandem solar cells with an all-solution processed multilayer structure utilizing a conventional structure composed of non-peripherally substituted octahexyl tetrabenzotriazaporphyrins and poly(3-hexylthiophene) (P3HT) as donors in the back and front cells, respectively. A transparent ZnO layer functions in electron transport for the front cell and as a stable foundation for the fabrication of the back cell to complete the tandem cell architecture. As a result, the tandem cell exhibited a relatively high open-circuit voltage of 1.4 V. Furthermore, by vapor-annealing treatment, the crystallization of the P3HT-conjugated polymer was improved and a PCE of 3.2% was achieved for the tandem cell with 5-min vapor-annealing treatment.

Triphenylamine-Thienothiophene Organic Charge-Transport Molecular Materials: Effect of Substitution Pattern on their Thermal, Photoelectrochemical, and Photovoltaic Properties

Two readily accessible thienothiophene-triphenylamine charge-transport materials have been synthesized by simply varying the substitution pattern of the triphenylamine groups on a central thienothiophene π-linker. The impact of the substitution pattern on the thermal, photoelectrochemical, and photovoltaic properties of these materials was evaluated and, based on theoretical and experimental studies, we found that the isomer in which the triphenylamine groups were located at the 2,5-positions of the thienothiophene core (TT-2,5-TPA) had better π-conjugation than the 3,6-isomer (TT-3,6-TPA). Whilst the thermal, morphological, and hydrophobic properties of the two materials were similar, their optoelectrochemical and photovoltaic properties were noticeably impacted. When applied as hole-transport materials in hybrid perovskite solar cells, the 2,5-isomer exhibited a power-conversion efficiency of 13.6 %, much higher than that of its 3,6-counterpart (0.7 %) under the same standard conditions.