Sn-Doped Zinc Oxide as an Electron Transporting Layer for Enhanced Performance in PbS Quantum Dot Solar Cells.

Colloidal PbS quantum dot solar cells (QDSCs) have been primarily demonstrated in n-i-p structures by incorporating a solution-processed ZnO electron transporting layer (ETL). Nevertheless, the inherent energy barrier for the electron extraction at the ZnO/PbS junction along with the defective nature significantly diminishes the performance of the PbS QDSCs. In this study, by employing Sn-doped ZnO (ZTO) ETL, we have tuned the conduction band offset at the junction from spike-type to cliff-type so that the electron extraction barrier can be eliminated and the overall photovoltaic parameters can be enhanced (open-circuit voltage of 0.7 V, fill factor over 70%, and efficiency of 11.3%) as compared with the counterpart with the undoped ZnO ETL. The X-ray photoelectron spectroscopy (XPS) analysis revealed a mitigation of oxygen vacancies in the ZTO ETL of our PbS QDSCs. Our work signifies the importance of Sn doping into the conventional ZnO ETL for the superior electron extraction in PbS QDSCs.

Pseudoxanthomonas sacheonensis sp. nov., isolated from BTEX-contaminated soil in Korea, transfer of Stenotrophomonas dokdonensis Yoon et al. 2006 to the genus Pseudoxanthomonas as Pseudoxanthomonas dokdonensis comb. nov. and emended description of the genus Pseudoxanthomonas.

A Gram-negative, strictly aerobic, rod-shaped bacterium, designated strain BD-c54(T), was isolated from BTEX (benzene, toluene, ethylbenzene and xylenes)-contaminated soil in Sacheon, Korea. Growth of strain BD-c54(T) was observed at 15-35 degrees C (optimum 25-30 degrees C) and pH 6.0-9.5 (optimum pH 7.0-8.0). The predominant fatty acids were iso-C(15:0), iso-C(17:1)omega9c, iso-C(11:0) 3-OH, iso-C(16:0), iso-C(11:0) and iso-C(17:0). The strain contained large amounts of phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol and a small amount of an unknown amino-group-containing polar lipid as polar lipids. The major quinone was ubiquinone-8 (Q-8) and the G+C content of the genomic DNA was 67.5 mol%. A phylogenetic analysis based on 16S rRNA gene sequences showed that strain BD-c54(T) formed a tight phylogenetic lineage with Pseudoxanthomonas yeongjuensis GR12-1(T) within the genus Pseudoxanthomonas and was most closely related to P. yeongjuensis GR12-1(T) and [Stenotrophomonas] dokdonensis DS-16(T), with 98.3 and 96.6% 16S rRNA gene sequence similarity, respectively. The DNA-DNA relatedness between strain BD-c54(T) and P. yeongjuensis GR12-1(T) was 24.5%. On the basis of chemotaxonomic data and molecular properties, strain BD-c54(T) represents a novel species within the genus Pseudoxanthomonas, for which the name Pseudoxanthomonas sacheonensis sp. nov. is proposed. The type strain is BD-c54(T) (=KCTC 22080(T) =DSM 19373(T)). In addition, the transfer of Stenotrophomonas dokdonensis to Pseudoxanthomonas as Pseudoxanthomonas dokdonensis comb. nov. and an emended description of the genus Pseudoxanthomonas are proposed.