Transparent metal electrodes from ordered nanosphere arrays

We show that perforated metal electrode arrays, fabricated using nanosphere lithography, provide a viable alternative to conductive metal oxides as transparent electrode materials. The inter-aperture spacing is tuned by varying etching times in an oxygen plasma, and the effect of inter-aperture “wire” thickness on the optical and electronic properties of perforated silver films is shown. Optical transmission is limited by reflection and surface plasmons, and for these results do not exceed 73%. Electrical sheet resistance is shown to be as low as 3 Ω ◻−1 for thermally evaporated silver films. The performance of organic photovoltaic devices comprised of a P3HT:PCBM bulk heterojunction deposited onto perforated metal arrays is shown to be limited by optical transmission, and a simple model is presented to overcome these limitations

Separation and identification of indene-C70 bisadduct isomers.

Following an initial work on the isolation of a single geometric isomer from an indene-C70 bisadduct (IC70BA) mixture, we report the full fractionation and identification of the bisadduct species in the material. Eleven fractions of IC70BA isomers were separated by high-performance liquid chromatography. A number of fractions contained relatively pure isomer species and their configuration were deduced using a variety of analytical techniques including (1)H and (13)C NMR and UV-vis spectroscopy. The electrochemical properties and the organic solar cell device performance were investigated for fractions where a reasonable quantity of sample could be isolated

Fabrication of nanostructures using atomic force microscope assisted nanolithography

Ph.DDOCTOR OF PHILOSOPH

Organic and Inorganic Blocking Layers for Solution-Processed Colloidal PbSe Nanocrystal Infrared Photodetectors

C1 - Journal Articles Referee

Enhancement of efficiency in organic photovoltaic devices containing self-complementary hydrogen-bonding domains

Self-complementary hydrogen-bonding domains were incorporated as the electron deficient unit in “push–pull”, p-type small molecules for organic photovoltaic active layers. Such compounds were found to enhance the fill factor, compared with similar non-self-organized compounds reported in the literature, leading to higher device efficiencies. Evidence is presented that the ability of these molecules to form one-dimensional hydrogen-bonded chains and subsequently exhibit hierarchical self-assembly into nanostructured domains can be correlated with improved device efficiency

Phthalimide and naphthalimide: Effect of end-capping groups on molecular properties and photovoltaic performance of 9-fluorenone based acceptors for organic solar cells

A novel 2-butyloctyl (BO) substituted\ua0phthalimide\ua0(PI) end-capped fluorenone [PI-FN-PI (BO)] non-fullerene\ua0electron acceptor\ua0for\ua0organic photovoltaics\ua0has been designed and synthesized to study the effect of end-capping groups on the\ua0optoelectronic\ua0properties compared to our earlier reported naphthalimide (NAI) terminated fluorenone\ua0NAI-FN-NAI (BO)\ua0reference compound. The electron withdrawing terminal NAI groups were replaced by a PI group in order to evaluate the influence of\ua0electron affinity\ua0of such group on the lowest occupied\ua0molecular orbital\ua0(LUMO) energy level and other optoelectronic properties. The newly synthesized\ua0PI-FN-PI (BO)\ua0with a 2-butyloctyl alkyl chain is sparingly soluble in\ua0organic solvents\ua0due to its more planar structure and short alkyl chain. For organic solar cell devices,\ua0solubility\ua0of the active layer blend is extremely important so higher solubility is the key requirement. In order to enhance the solubility of the compound, we synthesized 2-decyltetradecyl (DT) substituted phthalimide (PI) end-capped fluorenone [PI-FN-PI (DT)]. Furthermore, another new compound\ua0NAI-FN-NAI (DT)\ua0was produced to compare with\ua0PI-FN-PI (DT)\ua0since both of these compounds have similar side alkyl chain and middle core but different end capping groups. It is clearly demonstrated that this simple chemical modification noticeably influences thermal, optical,\ua0electrochemical properties\ua0and significantly impacts the\ua0photovoltaic performance

Alkyl Chain Length‐Dependent Amine‐Induced Crystallization for Efficient Interface Passivation of Perovskite Solar Cells

Abstract Efficient surface passivation of perovskite solar cells (PSC) using treatment with ammonium salts is demonstrated as an efficient method to enhance the device performance, owing to the affinity between the amine group and [PbI6]4− octahedron. However, due to their high solubility in polar solvents (DMF/DMSO), ammonium salts are more difficult to use in passivation of the interface between the electron transport layer and perovskite thin film in n‐i‐p structured PSCs. In this report, this work successfully links the amine group with a fullerene through a series of increasing carbon chain length, from two to twelve methylene units (FC‐X, X = 2, 6, 12), and then introduce the synthesized molecules as interface passivation layers into SnO2‐based planar n‐i‐p PSCs. Results show that the interface passivation effect is highly dependent on the side‐chain length, and the longer chain length amine‐functionalized fullerene is more beneficial for the device performance. A power conversion efficiency as high as 21.2% is achieved by using FC‐12. The surface energy, perovskite crystallite size and electron transfer capacity correlate with the linker chain length. This work develops an amine‐induced anchored crystallization of perovskite to unravel the mechanism of this passivation effect. As expected, enhanced device stability is also observed in the FC‐12 passivated PSCs

Naphthalimide end-capped diphenylacetylene: a versatile organic semiconductor for blue light emitting diodes and a donor or an acceptor for solar cells

A novel compound 6,6′-(ethyne-1,2-diylbis(4,1-phenylene))bis(2-(2-butyloctyl)-1H-benzo[de]isoquinoline-1,3(2H)-dione) (NAI-PVP-NAI) based on an end capping group 1,8-naphthalimide and central building block diphenylacetylene was designed and synthesized by Suzuki coupling. The newly synthesized NAI-PVP-NAI compound is characterized using optical, thermal, and electrochemical techniques as well as ab initio modeling. This novel and unique compound exhibits strong blue emission in the solid state and has been successfully used as an active light-emitting layer in organic light emitting diodes (OLEDs). Interestingly, the newly developed compound shows both electron-donating and electron-accepting abilities. Therefore, it can act as a donor or an acceptor organic semiconductor. Indeed, upon evaluating this molecule in solution processable organic photovoltaic (OPV) devices, we show that it acts as a donor when used with a PCBM acceptor and as an acceptor when used with a P3HT donor. Thus, NAI-PVP-NAI is a versatile compound, which can play three roles as a blue light emitting layer in OLEDs and a donor or an acceptor in OPV devices.</p