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Summary: An attempt is made to develop dye‐sensitized solar cell (DSSCs) with TiO2 hollow spheres for photoanode and natural dyes such as Tagetes, Acacia catechu, Punica granatum, Rubia tinctorum, Terminalia chebula and more importantly Biancaea sappan, the cotton dyeing extracts. Hydrothermally treated carbon spheres are used as the template for making the hollow spheres. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) positions of these dyes are analyzed using cyclic voltammogram, and spectroscopic techniques and then the fabrication of the solar cells with TiO2 hollow spheres were done accordingly. It is found that Punica granatum sensitized cell delivers a higher Power Conversion Efficiency (PCE) of 0.26% with the VOC of 0.53 V as expected. It is also found that though the dye from Acacia catechu exhibits low PCE, it possesses the highest fill factor of 85% and open‐circuit voltage (VOC) of 0.58 V. Also, these are found to have lower charge transfer resistance (Rct) and better temperature stability compared to the others. [ABSTRACT FROM AUTHOR]

Photoanodes made of highly oriented TiO2 nanorod (NR) arrays with different aspect ratios were synthesized via a one-step hydrothermal technique. Preferentially oriented single crystalline rutile TiO2 was confirmed by the single peak in an XRD pattern (2θ = 63°, (0 0 2)). FESEM images evidenced the growth of an array of NRss having different geometries with respect to reaction time and solution refreshment rate. The length, diameter and aspect ratio of the NRs increased with reaction time as 4 h (1.98 μm, 121 nm, 15.32), 8 h (4 μm, 185 nm, 22.70), 12 h (5.6 μm, 242 nm, 27.24) and 16 h (8 μm, 254 nm, 38.02), respectively. Unlike a conventional dye-sensitized solar cell (DSSC) with a liquid electrolyte, DSSCs were fabricated here using one-dimensional rutile TiO2 NR based photoanodes, N719 dye and a quasi-state electrolyte. The charge transport properties were investigated using current–voltage curves and fitted using the one-diode model. Interestingly the photovoltaic performance of the DSSCs increased exponentially with the length of the NR and was attributed to a higher surface to volume ratio, more dye anchoring, and channelized electron transport. The higher photovoltaic performance (Jsc = 5.99 mA cm−2, Voc = 750 mV, η = 3.08%) was observed with photoanodes (16 h) made with the longer, densely packed TiO2 NRs (8 μm, 254 nm). [ABSTRACT FROM AUTHOR]