Synthesis and characterization of organic conjugated polymer/ ZnO nano-particle films for solar cell application

Hybrid thin films show great promise as a novel material for solar energy conversion devices. Using present knowledge from polymer bulk hetero-junction solar cells, the design of a simple, and potentially low cost, hybrid solar cell based on metal oxides and conjugated polymers is presented. The hybrid material properties are often superior to the sum of the intrinsic properties of the components and often have a functionality that is not present in either of the individual materials [1]. In this research, hybridization of organic conducting polymer and metal oxide semiconductor on nanometer scale in fabricating of a bulk hetero-junction solar cell will be investigated. ZnO nanoparticles were chosen as nanoparticle semiconductors and Poly(3-hexylthiophene-2,5-diyl) (P3HT) is used as a conductive polymer. ZnO and P3HT are individually very important functional materials. Additionally, ZnO nanoparticles have transparency over the whole visible region and have good electron mobility compared to other wide band gap materials such as TiO2 [61,62]. The P3HT semiconductor polymer is important because of its high absorption coefficient in the visible region. In addition to the aforementioned intrinsic properties of these functional materials, in the hybrid of ZnO/P3HT energy levels of ZnO nanoparticles and P3HT polymer are matching and the hybrid layer can act as an active layer to absorb the visible solar light and release the electric charges. Uniform ZnO nanoparticles with small particle size distribution were synthesized. High resolution TEM imaging was performed to study the size and shape of the ZnO nanoparticles. The synthesized particles mainly range between 5-7 nm. To prepare the ZnO/P3HT hybrid solution we optimized the dispersion of the ZnO nanoparticles in the methanol/chloroform mixture solution (avoiding ZnO agglomeration). We obtained good dispersion of ZnO nanoparticles in a mixed solution of 4.5% methanol and 95.5% chloroform. Glass coated with ITO was used as a substrate followed by a poly (3,4ethylenedioxythiophene) poly (styrene sulfonate) (PEDOT:PSS) layer, spin coated on the ITO substrate. Above the PEDOT:PSS layer we spin coated a hybrid (ZnO/P3HT) layer followed by depositing aluminium electrodes using the metal evaporation technique. We studied the quality of the film formation and the aluminium electrodes using optical and scanning electron microscopies. Also we studied the absorption and emission hybrid films using UV-Visible and florescent spectroscopies. By changing the blend (ZnO/P3HT) concentration and the ratio of ZnO and P3HT as the initial parameters we could optimise the optical properties. 5 mg/mL ZnO nanoparticles and 10 mg/mL P3HT concentrations with 50% ZnO and 50% P3HT ratio resulted in the best optical characteristics in the hybrid films. The concentration of the PEDOT:PSS was also optimised. We found that 0.65% PEDOT:PSS concentration results the highest electrical measurements of the prepared Bulk heterojunction solar cell. Using the optimised parameters we prepared the bulk hetero-junction solar cells and conducted the electrical tests including incident photon to electron conversion efficiency IPCE and J-V characterization. We found that optimized parameters resulted in 19% IPCE and 1.13 mA.Cm-2 ISC and 0.23 VOC. We chose three prepared solar cells; 1. best performing with 50% -50% ZnO/P3HT ratio , 2.worst performing with 50% -50% ZnO/P3HT ratio 3. solar cell with 30%-70% ZnO/P3HT ratio) to study the morphology of their hybrid layer using AFM and surface profiler. Up to some extend we could understand and relate the hybrid film morphologies to the obtained electrical performance of these three bulk hetero-junction solar cells. In compar to other lab-prepared bulk hetero-junction solar cells the best performing bulk hetero-junction solar cell has a better hybrid film uniformity. Also in the best performing bulk hetero-junction solar cell the roughnesses and mean granular sizes of the film over the surface were very similar. We used AFM to correlate the quality of the film surface with the electrical performance and found that uniform and continuous films are very important in the performance of the solar cell device

Covalent modification of reduced graphene oxide with piperazine as a novel nanoadsorbent for removal of H2S gas

In the present research, piperazine grafted-reduced graphene oxide RGO-N-(piperazine) was synthesized through a three-step reaction and employed as a highly efficient nanoadsorbent for H2S gas removal. Temperature optimization within the range of 30–90 °C was set which significantly improved the adsorption capacity of the nanoadsorbent. The operational conditions including the initial concentration of H2S (60,000 ppm) with CH4 (15 vol%), H2O (10 vol%), O2 (3 vol%) and the rest by helium gas and gas hour space velocity (GHSV) 4000–6000 h−1 were examined on adsorption capacity. The results of the removal of H2S after 180 min by RGO-N-(piperazine), reduced graphene oxide (RGO), and graphene oxide (GO) were reported as 99.71, 99.18, and 99.38, respectively. Also, the output concentration of H2S after 180 min by RGO-N-(piperazine), RGO, and GO was found to be 170, 488, and 369 ppm, respectively. Both chemisorption and physisorption are suggested as mechanism in which the chemisorption is based on an acid–base reaction between H2S and amine, epoxy, hydroxyl functional groups on the surface of RGO-N-(piperazine), GO, and RGO. The piperazine augmentation of removal percentage can be attributed to the presence of amine functional groups in the case of RGO-N-(piperazine) versus RGO and GO. Finally, analyses of the equilibrium models used to describe the experimental data showed that the three-parameter isotherm equations Toth and Sips provided slightly better fits compared to the three-parameter isotherms

Nano-ZnO: An efficient and reusable catalyst for one-pot synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones and pyrazolo[1,2-a][1,2,4]triazole-1, 3-diones

The catalytic activity of nano-structured ZnO has been explored in the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione and pyrazolo[1,2-a][1,2,4]triazole-1,3- dione derivatives via a three-component coupling reaction between aromatic aldehydes, malononitrile, and phthalhydrazides or 4-arylurazoles, respectively. High yield, low reaction times, non-toxicity and recyclability of the catalyst, and easy work-up are the main merits of this protocol

High brightness illumination based on laser light diffusion with mie scattering

Limited luminous flux per wafer area of light emitting diodes (LEDs) for high power solid state illumination causes some packaging real estate issues. This problem can be tackled with laser diodes (LDs). At high current densities, LDs offer higher efficiency, however with very low etendue and divergent angle. This significantly increases the complexity of color conversion for white light generation. Concentrated light can carbonize the color conversion unit and have high speckle contrast. These problems can be addressed by efficient diffusion of the laser beam and this paper is aimed to introduce the first laser diffusion system based on TiO2 Mie particles. Based on a series of ray tracing simulations, an idealized cost-effective system is modeled and results showed an almost lossless diffusion with a guiding system based on reflection resulting in an almost uniform irradiance level with only 17% power loss. Furthermore, offered design can reduce the challenges for the compact packaging of white LDs by eliminating the heat sink for color conversion coating and enabling a safe light intensity for utilizing quantum dots for color engineering.TÜBİTA