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We use free-standing TiO2 nanotube membranes that are transferred onto FTO slides in front-side illuminated dye-sensitized solar cells (DSSCs). We investigate the key parameters for solar cell arrangement of self-ordered anodic TiO2 nanotube layers on the FTO substrate, namely the influence of the annealing procedure on the DSSC light conversion efficiency. The results show that using an optimal temperature annealing profile can significantly enhance the DSSC efficiency (in our case η = 9.8%), as it leads to a markedly lower density of trapping states in the tube oxide, and thus to strongly improved electron transport properties.

Double perovskite, Cs 2 AgBiBr 6 , is introduced as a lead-free perovskite solar cell. Device modeling of Cs 2 AgBiBr 6 (DP) was accomplished to obtain the optimum parameters using the Solar Cell Capacitance Simulator (SCAPS). Two devices with two different hole transport layers (HTLs) were investigated, including P 3 HT and Cu 2 O. For both devices with different HTLs, an optimal thicknesses of 1200 nm and defect densities of 1.0 ×10 14 cm -3 for DP layer were attained. For both HTLs, conduction band offset, CBO, is -0.21 eV and valence band offset, VBO, is +0.16 eV. For shallow acceptor doping concentration of P 3 HT and Cu 2 O, the values of 5.0 × 10 19 and 5.0 × 10 17 cm −3 were obtained, respectively. As far as the shallow donor density of electron transport layers (ETLs) is concerned, for both cases, the optimum value of 5.0 × 10 19 cm -3 were achieved. For capture cross section, , , in absorber layer for both HTLs, the optimal value at , of 10 −20 cm 2 for , (defect density of DP) is 10 16 cm −3 , at , of 10 −19 cm 2 for , is 10 15 cm −3 , at , of 10 −18 cm 2 for , is 10 14 cm −3 , at , of 10 −17 cm 2 for , is 10 13 cm −3 , and at , of 10 −16 cm 2 for , is 10 12 cm −3 . For P 3 HT device, the interface defect density of P 3 HT/Cs 2 AgBiBr 6 is occurred at 1.0×10 14 cm -2 , and for Cs 2 AgBiBr 6 /SnO 2 is happened at 1.0×10 9 cm -2 . For Cu 2 O device, the interface defect density of Cu 2 O/ Cs 2 AgBiBr 6 is befallen at 1.0×10 13 cm -2 , and for Cs 2 AgBiBr 6 /SnO 2 is happened at 1.0×10 10 cm -2 . As for radiative recombination, for P 3 HT device, the optimal value is happened at 2.3×10 -13 cm 3 /s, however, for Cu 2 O device is occurred at 2.3×10 -12 cm 3 /s. Finally, for P 3 HT device, a maximum power conversion efficiency, PCE, of 11.69% (open-circuit voltage, V oc , of 2.02 V, short-circuit current density, J sc , of 6.39 mA/cm 2 , and fill-factor, FF, of 0.90 (90% )) were achieved, and for Cu 2 O device, a PCE of 11.32% (V oc of 1.97 V, J sc of 6.39 mA/cm 2 , and FF of 0.895 (89.5% )) were attained. This is the highest efficiency for Cs 2 AgBiBr 6 double perovskite solar cell which was achieved till now. Finally, our results are providing towards fabricating a lead-free and inorganic solar cell.Keywords Cs 2 AgBiBr 6 . Double perovskite solar cell. Lead-free perovskite. Conduction band offset (CBO). Valence band offset (VBO). SCAPS

In the present work we compare TiO 2 nanotube lift-off strategies for the construction of front-side illuminated dye-sensitized solar cells (DSSCs). Anodic nanotube layers were detached from the metallic back contact by using different techniques and transferred onto an FTO substrate. We show that if we use an optimized potential step treatment to fabricate membranes, DSSC cell efficiencies can be significantly increased (η > 8%).This improved efficiency is ascribed to higher specific dye-loading and enhanced electron transport properties of optimally fabricated TiO 2 nanotube membranes.

We examine the ordering properties of rectangular hard rods with length L and diameter D at a single planar wall and between two parallel hard walls using the second-virial density functional theory. The theory is implemented in the three-state Zwanzig approximation, where only three mutually perpendicular directions are allowed for the orientations of hard rods. The effect of varying shape anisotropy is examined at / 10, 15 LD  and 20. In contact with a single hard wall, the density profiles show planar ordering, damped oscillatory behavior, and wall induced surface ordering transition below the coexisting isotropic density of bulk isotropic-nematic (I-N) phase transition. Upon approaching the coexisting isotropic density, the thickness of nematic film diverges logarithmically, i.e. the nematic wetting is complete for any shape anisotropy. In the case of confinement between two parallel hard walls, it is found that the continuous surface ordering transition depends strongly on the distance between confining walls (H) for HL  , while it depends weakly on H for HL  . The minimal density at which a surface ordering transition can be realized is located at around ~2 HD for all studied shape anisotropies due to the strong interference effect between the two hard walls. The first order I-N phase transition of the bulk system becomes surface ordered isotropic

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The stability of demixing phase transition in binary mixtures of hard plates (with thickness L and diameter D) and hard spheres (with diameter ) is studied by means of Parsons-Lee theory. The isotropic-isotropic demixing, which is found in mixtures of large spheres and small plates, is very likely to be preempted by crystallization. In contrast, the nematic-nematic demixing, which is obtained in mixtures of large plates and small spheres, can be stabilized at low diameter ratios (/D) and aspect ratios (L/D). At intermediate values of /D, where the sizes of the components are similar, neither the isotropic-isotropic nor the nematic-nematic demixing can be stabilized, but a very strong fractionation takes place between a plate rich nematic and a sphere rich isotropic phases. Our results show that the excluded volume interactions are capable alone to explain the experimental observation of the nematic-nematic demixing, but they fail for the description of isotropic-isotropic one (Chen et. al., Soft Matter, 11, 5775 (2015)).3