The main objective of this study is to show the effect of TiO₂ nanotube length, diameter and intertubular lateral spacings on the performance of back illuminated dye sensitized solar cells (DSSCs). The present study shows that processing short TiO₂ nanotubes with good lateral spacings could significantly improve the performance of back illuminated DSSCs. Vertically aligned, uniform sized diameter TiO₂ nanotube arrays of different tube lengths have been fabricated on Ti plates by a controlled anodization technique at different times of 24, 36, 48 and 72 h using ethylene glycol and ammonium fluoride as an electrolyte medium. Scanning electron microscopy (SEM) showed formation of nanotube arrays spread uniformly over a large area. X-ray diffraction (XRD) of TiO₂ nanotube layer revealed the presence of crystalline anatase phases. By employing the TiO₂ nanotube array anodized at 24 h showing a diameter ∼80 nm and length ∼1.5 𝜇m as the photo-anode for back illuminated DSSCs, a full-sun conversion efficiency (𝜂) of 3.5%was achieved, the highest value reported for this length of nanotubes.

In this paper, we report on the high electrical storage capacity of composite electrodes made from nanoscale activated carbon combined with either poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) or PEDOT doped with multiple dopants such as ammonium persulfate (APS) and dimethyl sulfoxide (DMSO). The composites were fabricated by electropolymerization of the conducting polymers (PEDOT:PSS, doped PEDOT) onto the nanoscale activated carbon backbone, wherein the nanoscale activated carbon was produced by ball-milling followed by chemical and thermal treatments. Activated carbon/PEDOT:PSS yielded capacitance values of 640 F g^-1 and 26mF cm^-2, while activated carbon/doped PEDOT yielded capacitances of 1183 F g^-1 and 42 mF cm^-2 at 10 mV s^-1. This is more than five times the storage capacity previously reported for activated carbon–PEDOT composites. Further, use of multiple dopants in PEDOT improved the storage performance of the composite electrode well over that of PEDOT:PSS. The composite electrodes were characterized for their electrochemical behaviour, structural and morphological details and electronic conductivity and showed promise as high-performance energy storage systems.

In this paper, we report on the electrochemical characteristics of graphene–PEDOT composite electrodes. The electrodes were made of indium tin oxide (ITO) substrates by simple processes of electrophoretic deposition of graphene followed by electropolymerization of EDOT monomer. The composite electrode was obtained by electrochemical measurements, a median specific capacitance of 1410 F/g and a median area capacitance of 199 mF cm⁻² at a scan rate of 40 mVs⁻¹. The composite showed good stability characteristics after repeated scans in cyclic voltammmetry and fared much better than a thin film of PEDOT. The thermal stability of the composite is also much superior when compared to the polymer with a weight loss temperature of 350° C for the composite and 250° C for the polymer, respectively. The above electrochemical and thermal behaviours of the composite are correlated to the unique morphology of electrodeposited graphene that provides a conductive and high surface area template for electropolymerization.

In contrast to the conventional DSSC systems, where the dye molecules are used as light harvesting material, here a solid-state absorber was used as a sensitizer in conjunction with the dye. The materials like ZnO and Al₂O₃ : C, which will show optically stimulated luminescence (OSL) upon irradiation were used as extremely thin absorber layers. This novel architecture allows broader spectral absorption, an increase in photocurrent, and hence, an improved efficiency because of the mobility of the trapped electrons in the absorber material after irradiation, to the TiO₂ conduction band. Nanocrystalline mesoporous TiO₂ photoanodes were fabricated using these solid-state absorber materials and after irradiation, a few number of samples were co-sensitized with N719 dye. On comparing both the dye loaded photoanodes (ZnO/TiO₂ and Al₂O₃ : C/TiO₂), it can be concluded from the present studies that, the Al₂O₃ : C is superior to ZnO under photon irradiation. Al₂O₃ : C is more sensitive to photon irradiation than ZnO and hence there can be more trap centres produced in Al₂O₃ : C.