“…The DSC is based on a sensitized thin film of nanostructured, mesoporous TiO 2 , which is an attractive low-cost, nontoxic, wide band gap semiconductor, with excellent chemical stability and (photo)catalytic activity, specifically as a nanostructured material. ,,− A wide variety of synthesis methods have been developed to tune the crystal phase, nanoparticle size and morphology, and the resulting optical, physical, and chemical properties. ,,− The three main crystal phases are anatase, rutile, and brookite; the first two phases have a tetragonal crystal structure, whereas brookite is orthorhombic. ,, TiO 2 -based DSCs are generally fabricated using pure anatase nanoparticulate films to achieve the highest efficiencies; however, other phases of TiO 2 may be equally attractive. ,− Several reports exist on the use of either rutile or brookite nanomaterials but generally the efficiency is found to be lower; however, especially brookite has shown promise exhibiting a larger open-circuit voltage than anatase-based solar cells. − Although both materials are TiO 2 , significant differences may exist in several crucial parameters, including the energetic position of the conduction band, the distribution and density of trap states, electron mobility, and the rate constant for electron-transfer rate to the solution. , Both rutile and brookite are much more difficult to synthesize in nanoparticulate morphology related to a higher surface energy, and it is particularly complicated to obtain brookite nanomaterials of high purity. ,,,, Hence, most of the reports in the literature on the applications of brookite in DSC actually use brookite–anatase mixed materials, which complicates the analysis of the performance. In a recent paper, the synthesis of pure brookite nanomaterials has been described, and it is concluded that a combination of lower dye loading with lower collection efficiency results in a lower solar cell efficiency for the brookite-based cells, despite a higher open-circuit voltage .…”