Takaya Kubo

Optical gaps and electrochromic efficiencies of sputtered tungsten oxide films are studied by focusing attention on the cluster size of the film. The cluster consists of O‐W‐O network with terminal W=O bonds on its boundary. The quantity of W=O bonds increased with the surface area of the clusters. Raman scattering bands of the O‐W‐O and W=O are observed between 500 and 1100 cm−1. These characteristic Raman scattering bands of the film are well reproduced by the combination of four Gaussian shap

AgBiS₂ nanocrystals (NCs) are nontoxic, lead-free, and near-infrared absorbing materials. Eco-friendly solar cells were constructed using interdigitated layers of ZnO nanowires (NWs) and AgBiS₂ NCs, with the aim of elongating the otherwise short carrier diffusion length of the AgBiS₂ NC assembly. AgBiS₂ NCs were uniformly infiltrated into the ZnO NW layers using a low-cost and easily scalable dip coating method. The resulting ZnO NW/AgBiS₂ N

We have constructed heterojunction iodide ligand PbS quantum dot (QD) and ZnO nanowire (NW) solar cells. In these interdigitated structures, PbS QDs are well-embedded within ZnO NWs grown on a dense ZnO layer. A Au back contact is directly formed on the iodide ligand PbS QD surface layer. In the widely studied colloidal QD-based heterojunction solar cells, the PbS QD active layer is sandwiched between the hole-blocking layer (or electron-accepting layer) and the electron-blocking layer (EBL) (or

PbS colloidal quantum dot (CQD)‐based depleted bulk‐heterojunction solar cells were constructed, using the 1.2 μm thick nanowire array infiltrated with PbS QDs bearing Br ligands. The long‐term stability tests were performed on the solar cells without encapsulation in air under continuous light soaking using a Xe lamp with an AM1.5G filter (100 mW cm −2 ). Time course of solar cell performances during the tests showed two time periods with distinct behavior, that is, the initial transient time p

Eco-friendly solar cells were fabricated using interdigitated layers comprising ZnO nanowires (NWs) and infrared absorbing AgBiS₂ nanocrystals (ITO/ZnO NWs/AgBiS₂/P3HT/Au). The quality of ZnO NWs was studied using photoluminescence and Raman spectroscopy to identify the defects in ZnO NWs influencing solar cell performance. Oxygen vacancies and Zn interstitial sites, among various recombination sites, were observed to be the main sites for carrier recombination, which hinde

We constructed an infrared PbS colloidal quantum dot (QD)/ZnO nanowire (NW) solar cell to develop a solution-processed bottom solar cell for multijunction solar cells. PbS QD/ZnO NW interdigitated structures comprising 1 μm long ZnO NWs enable the construction of spatially separated carrier pathways and thick PbS QD layers for high infrared light harvesting. Additionally, optical management plays an essential role in the harvesting process. Using infrared transparent conductive oxides as window