We report all solid-state nanostructured inorganic-organic heterojunction solar cells fabricated by depositing Sb(2)S(3) and poly(3-hexylthiophene) (P3HT) on the surface of a mesoporous TiO(2) layer, where Sb(2)S(3) acts as an absorbing semiconductor and P3HT acts as both a hole conductor and light absorber. These inorganic-organic light harvesters perform remarkably well with a maximum incident-photon-to-current efficiency (IPCE) of 80% and power conversion efficiency of 5.13% under air-mass 1.5 global (AM 1.5G) illumination with the intensity of 100 mW cm(-2). These devices are highly stable under room light in air, even without encapsulation. The present findings offer novel directions for achieving high-efficiency solid-state solar cells by hybridization of inorganic-organic light harvesters and hole transporters.

We review two types of inorganic nanomaterials-metal chalcogenide quantum dots (QDs) and lead halide perovskites-that serve as prospective light harvesters in hybrid mesoscopic solar cells. Metal chalcogenide QDs are introduced in three parts: chalcogenides of cadmium (CdS, CdSe and CdTe), chalcogenides of lead (PbS and PbSe) and chalcogenides of antimony (Sb 2 S 3 and Sb 2 Se 3). The devices made using these chalcogenide QDs in a liquid-type electrolyte showed the best cell efficiencies, ranging from 3 to 6%. For solid-state QD-sensitized solar cells (QDSCs), the device performances were generally poor; only devices made of Sb 2 S 3 and PbS QDs attained cell efficiencies approaching B7%. In contrast, nanocrystalline lead halide perovskites have emerged since 2009 as potential photosensitizers in liquid-type sensitized TiO 2 solar cells. In 2012, the efficiencies of the all-solid-state perovskite solar cells were enhanced to 9.7 and 10.9% using anodes of TiO 2 and Al 2 O 3 films, respectively, with 2,2 0 ,7,7 0-tetrakis-(N,N-dip -methoxyphenylamine)9,9 0-spirobifluorene (spiro-OMeTAD) as a holetransporting material. In 2013, the performance of a TiO 2 solar cell sensitized with lead iodide perovskite (CH 3 NH 3 PbI 3) was optimized further to attain an overall power conversion efficiency g ¼ 15%, which is a new milestone for solar cells of this type having a device structure similar to that of a dye-sensitized solar cell.

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Iodide redox (3I À /I 3 À ), polysulfide redox (S 2À /S x 2À ), organic redox [TMTU/TMFDS 2+ : tetramethylthiourea/tetramethylformaminium-bis(trifluoromethanesulfonyl)imide], ferrocene redox (Fc/Fc + ), nickel redox [Ni(II)/Ni(III)], and cobalt redox [Co(II)/Co(III)] hole conducting electrolytes were systematically investigated to determine their suitability for use in Sb 2 S 3 -sensitized photoelectrochemical solar cells. A long-term stability test and UV-visible spectral analyses revealed that Sb 2 S 3 -sensitized photoelectrochemical solar cells worked stably with Co(II)(o-phen) 3 (TFSI) 2 /Co (III)(o-phen) 3 (TFSI) 3 [TFSI: bis(trifluoromethanesulfonyl)imide] as the redox mediator.