Self-Assembly of Silver and Gold Nanoparticles in a Metal-Free Phthalocyanine Liquid Crystalline Matrix: Structural, Thermal, Electrical and Nonlinear Optical Characterization

Abstract

The properties of self-assembled supramolecular structures change remarkably upon the dispersion of a minute amount of metal nanoparticles in them. Here we present, for the first time, investigations of the effect of dispersing alkyl thiol functionalized group-XI metal nanoparticles (silver and gold) in a phthalocyanine-based discotic liquid crystal on their structural, electrical, thermal and nonlinear optical transmission properties, and supramolecular order. Results indicate uniform dispersion of about 0.5-3 % metal nanoparticles in the columnar matrix which results in an increase of the electrical conductivity of the system by two to four orders of magnitude, without disrupting the mesophase. We also show that dispersing metal nanoparticles in these nanocomposites enhances their nonlinear optical absorption, when measured under excitation by nanosecond laser pulses at 532 nm. These results indicate that the present self-assembling supramolecular soft nanocomposites are potential candidates for applications in optoelectronic devices such as thin film transistors, photovoltaic solar cells, and optical limiters.[a] A.

Liquid crystals in photovoltaics: a new generation of organic photovoltaics

“…107 High EQE of 470% in the Q-band absorption region of C6PcH2 and a high energy-conversion efficiency of 3.1% were achieved with different compositions of both donor and acceptor materials. The values of V OC is 0.81 V, I SC of 9.6 mA cm − 2 and FF of 40% were observed for the solar cell with the C6PcH2:PC 61 BM composite layer at a weight ratio of 2:1. To improve the FF of the above device, they studied the optimization of the active layer thickness and insertion of buffer layer.…”

“…The UV-ozone treatment of ITO decreases V OC , whereas it increases on the argon plasma treatment. 121 In 2010, Jeong et al 71 used TP discotics as an additive to well-established P3HT:PC 61 BM BHJ OPV device to realize the effect on PCE. The devices configured with P3HT:PC 61 BM (1:1.2 w-w) layer doped with 2,3,6,7,10,11-hexaacetoxytriphenylene (3 wt%) exhibit an average PCE of 3.97% after thermal annealing.…”

“…57 In another innovative approach, we realized that the conductivity of DLCs can be enhanced by several orders of magnitude by dispersing a very small amount of metallic, semiconducting or carbon nanoparticles. [58][59][60][61][62][63][64][65][66][67] Since the discovery of DLCs, there has been tremendous interest in utilizing these materials as one-dimensional semiconductors. Conducting and photoconducting properties of DLCs have been studied extensively.…”

Recent Advances in Discotic Liquid Crystal-Assisted Nanoparticles

“…We also investigated the self-assembled supramolecular structures of metal nanoparticles (gold and silver) in the columnar phase of metal free phthalocyanine DLCs [ 66 ]. The results clearly describe the uniform dispersion of NPs in columnar mesophase of phthalocyanine DLCs enhance the electrical conductivity of the nanocomposites up to four orders of magnitude without altering columnar phase.…”

“…Combining nanomaterials in DLCs has been fast growing current hot research topic in which number of intriguing marvels have been demonstrated and accordingly such DLC-NPs hybrid systems may be useful for various device applications. We initiated this research program by dispersing various functionalized NPs in different DLCs [ 13 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 , 68 , 69 , 70 , 71 ]. Some aspects of DLC-NP composites are presented here.…”