A perspective of mesoscopic solar cells based on metal chalcogenide quantum dots and organometal-halide perovskites

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 (Sb2S3 and Sb2Se3). 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 Sb2S3 and PbS QDs attained cell efficiencies approaching similar to 7%. In contrast, nanocrystalline lead halide perovskites have emerged since 2009 as potential photosensitizers in liquid-type sensitized TiO2 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 TiO2 and Al2O3 films, respectively, with 2,20,7,70-tetrakis-(N, N-di-p-methoxyphenylamine) 9,9'-spirobifluorene (spiro-OMeTAD) as a holetransporting material. In 2013, the performance of a TiO2 solar cell sensitized with lead iodide perovskite (CH3NH3PbI3) was optimized further to attain an overall power conversion efficiency eta = 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.