Dye-sensitized photocathodes have the potential to significantly contribute to the efficiency of the solar light-to-current conversion in tandem dyesensitized solar cells (DSSCs). A novel, highly porous nanoarchitecture of NiO is developed in this project. The spongelike material is grown by anodization, shows a virtually crack-free morphology, strongly adheres to the substrate, and can be grown with a controllable thickness of at least up to 6.5 μm. The oxide composition is NiO and the nanosponge exhibits p-type semiconductive behavior. A doubling of the maximum reported p-type DSSC efficiency compared to coumarin C343-sensitized NiO nanoparticle photocathodes can be achieved with the NiO nanosponge. The developed dye-sensitized p-type NiO-based cathodes are promising for application as photocathodes in tandem DSSC devices.
In the present work, a new solution processed nanohybrid system comprising of single-wall carbon nanotubes (SWCNTs) loaded by PbS quantum dots (QD) capped with an epitaxial ligand shell of methylammonium lead iodide perovskite clusters (MA 4 PbI 6 ) is designed and fabricated. Attachment of PbS/ PbI 6 QDs on the surface of SWCNT is followed and evidenced by performing Fourier Transform Infrared Spectroscopy, X-ray photoelectron spectroscopy, and Field Emission Scanning Electron Microscopy. The steady state and dynamic photoluminescence results reveal efficient charge transfer from photo-excited PbS/PbI 6 to SWCNTs. Very low amount (0.3 wt.%) of the as-synthesized PbS/ PbI 6 -SWCNT is further incorporated into a polymeric solar cell containing P3HT and PC 61 BM and exhibits a power conversion efficiency improvement of around 15% compared to the P3HT:PC 61 BM bulk heterojunction reference solar cell. Significantly, loading perovskite capped PbS QDs on the surface of SWCNT works more efficient rather than incorporating PbS/PbI 6 or SWCNT separately onto the composition of the photoactive layer. While PbS/PbI 6 broaden the absorption window of photoactive layer and enhance the photon harvesting, their loading on the SWCNT has a significant influence on the faster exciton splitting by efficient electron transfer as well as keeping the desired crystallinity and nanoscale morphology of host matrix upon addition of QDs. comprised of p-doped (electron donor) and n-doped (electron acceptor) semiconducting materials. [4][5][6][7] Nevertheless inefficient exciton dissociation, low carrier mobility, and incomplete harvesting of the solar spectrum remain as bottlenecks for the ultimate device performance of organic solar cells. [8,9] The idea of incorporating a second photo absorber such as low band gap polymers, [10][11][12][13][14][15][16][17][18] small molecules, [19][20][21] and dyes [19][20][21][22][23][24] has been used to tackle the latter problem. Colloidal semiconductor nanocrystals or quantum dots (QDs) have shown promising applicability in solution-processed transistors, solar cells, and other optoelectronic devices due to their high absorption coefficient, tunable band gap, multiple exciton generation with single photon absorption, tunable energy levels, slow exciton relaxation, and low cost. [25][26][27][28][29] In this sense, lead chalcogenide QDs such as PbS [30,31] and PbSe [32,33] are of particular interest due to their specific advantages, such as the narrow band gap (e.g., 0.41 and 0.28 eV for bulk PbS and PbSe, respectively) and large excitonic
In this article, the mutual solubility of tocopherols from crude palm oil was studied using carbon dioxide as a solvent at the temperatures of 80, 100 and 120 °C. Each sample from the phase equilibrium unit contained two parts. The liquid part was analyzed by gas chromatography (GC) in order to measure the tocopherol composition and, on the other hand, the vapor phase was conducted in an expansion vessel in order to measure the pressure increment during the expansion process. Two phase equilibrium data was calculated using the liquid phase composition and pressure increments during the expansion process. Results showed that the maximum solubility of tocopherols was around 2.27% at a temperature of 120 °C and at pressure of 5.44 MPa.
TiO 2 nanocrystals (NCs) with sizes around 20 nm were synthesized by hydrothermal method in acidic autoclaving pH. The hydrothermally grown TiO 2 NCs and P25 TiO 2 nanoparticles (NPs) were used in the preparation of two different pastes using different procedures. These pastes with different characteristics were separately deposited on FTO glass plates to form multilayer photoanodes of the dye-sensitized solar cells. The aim of this study was to search how a thin sub-layer of the hydrothermally grown TiO 2 NCs in the photoanodes could improve the efficiency of TiO 2 P25-based solar cells. The highest efficiency of 6.5% was achieved for a cell with a photoanode composed of one transparent sub-layer of hydrothermally grown TiO 2 NCs and two over-layers of P25 NPs. Higher energy conversion efficiencies were also attainable using two transparent sub-layers of hydrothermally grown TiO 2 NCs. In this case, an efficiency of 7.2% was achieved for a cell with a photoelectrode made of one over-layer of P25 TiO 2 NPs. This could show an increase of about 30% in the efficiency compared to the similar cell with a photoanode made of two layers of hydrothermally grown TiO 2 NCs. Keywords. Dye-sensitized solar cells; hydrothermal method; TiO 2 nanocrystals; multilayer photoanodes; energy conversion efficiency.
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