CdSe quantum dot-sensitized, nanoporous p-type nio photocathodes for quantum dot-sensitized solar cells

CdSe quantum dots (QDs) were deposited on a p-type nanoporous NiO surface by repeating the successive ionic layer adsorption and reaction (SILAR) procedure 6, 9, 12, and 15 times. The NiO/CdSe prepared using 12 SILAR cycles, which is denoted as the NiO/CdSe(12), exhibited a larger QD size and better QD coverage on the nanoporous NiO than the NiO films with CdSe(6) and CdSe(9), leading to better light absorption over longer wavelengths and a significantly increased hole lifetime. The resulting quantum dot-sensitized solar cell (QD-SSC) exhibited significantly enhanced cell efficiency (0.35%) compared to that (0.013%) of the QD-SSC with the NiO/CdSe(6). NiO/CdSe(15), however, exhibited a lower hole lifetime and hindered ion transport as a result of the agglomeration of QDs as well as the severely blocked pores of the nanoporous NiO, causing a significantly reduced cell efficiency for QD-SSCs with NiO/CdSe(15).