Naked metallic and semiconducting single-walled carbon nanotubes (SWNTs) were dissolved in organic solutions by derivatization with thionychloride and octadecylamine. Both ionic (charge transfer) and covalent solution-phase chemistry with concomitant modulation of the SWNT band structure were demonstrated. Solution-phase near-infrared spectroscopy was used to study the effects of chemical modifications on the band gaps of the SWNTs. Reaction of soluble SWNTs with dichlorocarbene led to functionalization of the nanotube walls.

No abstract

Single-walled carbon nanotube (SWNT)-polymer composites have been fabricated to evaluate the electromagnetic interference (EMI) shielding effectiveness (SE) of SWNTs. Our results indicate that SWNTs can be used as effective lightweight EMI shielding materials. Composites with greater than 20 dB shielding efficiency were obtained easily. EMI SE was tested in the frequency range of 10 MHz to 1.5 GHz, and the highest EMI shielding efficiency (SE) was obtained for 15 wt % SWNT, reaching 49 dB at 10 MHz and exhibiting 15-20 dB in the 500 MHz to 1.5 GHz range. The EMI SE was found to correlate with the dc conductivity, and this frequency range is found to be dominated by reflection. The effects of SWNT wall defects and aspect ratio on the EMI SE were also studied.

No abstract

Small molecules, namely, DCAO(3)TBDT and DR(3)TBDT, with 2-ethylhexoxy substituted BDT as the central building block and octyl cyanoacetate and 3-ethylrhodanine as different terminal units with the same linkage of dioctyltertthiophene, have been designed and synthesized. The photovoltaic properties of these two molecules as donors and fullerene derivatives as the acceptors in bulk heterojunction solar cells are studied. Among them, DR(3)TBDT shows excellent photovoltaic performance, and power conversion efficiency as high as 7.38% (certified 7.10%) under AM 1.5G irradiation (100 mW cm(-2)) has been achieved using the simple solution spin-coating fabrication process, which is the highest efficiency reported to date for any small-molecule-based solar cells. The results demonstrate that structure fine turning could cause significant performance difference and with that the performance of solution-processed small-molecule solar cells can indeed be comparable with or even surpass their polymer counterparts.

No abstract

In the past few years, great progress has been made in organic photovoltaic (OPV) cells for an alternate of silicon semiconductorbased solar cells. OPV has the advantages of clean, low-cost, flexibility, and the possibility of roll-to-roll production. [1][2][3][4] Currently, most of the works have been focused on polymer donor molecules using bulk heterojunction (BHJ) architecture and [6,6]-phenyl-C61-butyric acid methyl ester (PC 61 BM) as the acceptor. [5,6] Indeed, in addition to the currently better OPV performance than small molecules, polymers have the advantages for such as better film forming quality and so on. [7] However, it cannot be denied that there are disadvantages for polymer-based OPV, such as batch to batch reproducibility, difficulty of purification, and so on. In contrast, small molecules intrinsically do not have such flaws; [8] additionally, their band structures could be tuned easily with much more choices of chemical modification. Furthermore, small molecules generally have higher charge mobility and open voltages. [9,10] However, even with these advantages, small-molecule-based OPV cells have not been investigated as intensively as that of their polymer counterparts because one of the major problems for small molecules is their generally poor film quality when using the simple solution spinning process. [11] This has been hampering their performance, and indeed their power conversion efficiencies (PCEs) (4%-5%) [12][13][14][15][16][17][18] are still significantly lower compared with that (>7%) [19][20][21][22][23][24][25] from polymers. It is thus expected that better PCE could be achieved when their intrinsic bad film quality and morphology in BHJ architecture could be improved combining with their other advantages. But to achieve this, careful molecule design has to be carried out to address many factors collectively, including their molar absorption, morphology compatibility with the acceptors for a better film quality, and so on.Previously, we have reported a small molecule (DCAO7T, Scheme 1), which gives rather high quality of solution spincoated film and a high 5.08% PCE. [12] But this molecule comes with an end unit of cyanoacetate group, which could not contribute too much for the overall solar absorption. So, we thought that the current density J sc might be able to be enhanced if structures with stronger molar absorption is used to replace such an end unit, in the conditions that overall molecular backbone and morphology will not be affected too much. Considering the generally high absorption coefficients and good OPV performance of many dye molecules, such as triarylamines, [16,26] acenaphthoquinoxaline, [27] diketopyrrolopyrroles (DPP), [17] squaraines, [18,28,29] merocyanine, [30,31] isoindigo, [32] pthalocyanine, [33] and dipyrromethene boron difluoride (BODIPY), [34][35][36] we thus introduce a new dye unit, 3-ethylrhodanine, into the targeted OPV molecule named as DERHD7T (Scheme 1) with a conjugated thiophene backbone. With such a design, DERHD7T is expected to have a str...

No abstract