Mahmood Khalid, Swain Bhabani Sankar, Han Gill-Sang, Kim Byeong-Jo, Jung Hyun Suk
School of Advanced Materials Science & Engineering, Sungkyunkwan University , Suwon 440-746, Republic of Korea.
ACS Appl Mater Interfaces. 2014 Jul 9;6(13):10028-43. doi: 10.1021/am500105x. Epub 2014 Jun 18.
The realization of arrays of high-aspect-ratio nitrogen-doped ZnO (NZO) nanorod is critical to the development of high-quality nanostructure-based optoelectronic and electronic devices. In this study, we used a solution-based method to grow arrays of vertically aligned high-aspect-ratio NZO nanorods on ZnO seed layer covered fluorine-doped tin oxide substrates. We investigated whether the diameters and aspect ratios of the nanorods were affected by the addition of polyethylenimine (PEI) to the precursor solution used as well as by variations in the growth temperature and the concentration of the precursor solution. The performances of dye-sensitized solar cells (DSSCs) in which the synthesized high-aspect-ratio NZO nanorods were used as the photoanode material were also studied. That the dopant, nitrogen, was introduced into the ZnO lattice was confirmed using X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy. It was seen that after the addition of PEI, the NZO and ZnO nanorod arrays increased in length and their diameters became smaller (i.e., their aspect ratios increased). This resulted in an increase in the amount of dye absorbed by them, leading to improvements in the DSSCs based on the nanorods. The structural, morphological, optical, and photovoltaic characteristics of ZnO and NZO nanorod arrays synthesized using different precursor concentrations and growth temperatures (160-190 °C) were also examined. We also investigated the effect of the use of PEI on these characteristics. The power conversion efficiency (PCE) of DSSCs fabricated using the NZO nanorod arrays was found to be significantly higher than that of DSSCs based on the pure ZnO nanorod arrays. This increase in efficiency could be attributed to the combined effects of the increase in the charge-carrier concentration, change in morphology, and increase in the Fermi energy levels of the nanorods, which resulted because of N doping. A PCE of 5.0% was obtained for a DSSC based on a film of arrays of NZO nanorods having an aspect ratio of ∼47 and synthesized using PEI.
实现高纵横比的氮掺杂氧化锌（NZO）纳米棒阵列对于开发高质量的基于纳米结构的光电器件和电子器件至关重要。在本研究中，我们采用基于溶液的方法，在覆盖有氟掺杂氧化锡的氧化锌籽晶层上生长垂直排列的高纵横比NZO纳米棒阵列。我们研究了纳米棒的直径和纵横比是否受到添加到前驱体溶液中的聚乙烯亚胺（PEI）以及生长温度和前驱体溶液浓度变化的影响。还研究了将合成的高纵横比NZO纳米棒用作光阳极材料的染料敏化太阳能电池（DSSC）的性能。使用X射线光电子能谱和能量色散X射线光谱证实了掺杂剂氮被引入到ZnO晶格中。可以看出，添加PEI后，NZO和ZnO纳米棒阵列的长度增加，直径变小（即纵横比增加）。这导致它们吸收的染料量增加，从而使基于纳米棒的DSSC得到改进。还研究了使用不同前驱体浓度和生长温度（160 - 190°C）合成的ZnO和NZO纳米棒阵列的结构、形态、光学和光伏特性。我们还研究了使用PEI对这些特性的影响。发现使用NZO纳米棒阵列制造的DSSC的功率转换效率（PCE）明显高于基于纯ZnO纳米棒阵列的DSSC。效率的提高可归因于电荷载流子浓度的增加、形态的变化以及由于N掺杂导致的纳米棒费米能级的增加的综合作用。对于基于纵横比约为47且使用PEI合成的NZO纳米棒阵列薄膜的DSSC，获得了5.0%的PCE。
