Improved optical absorption of silicon single-nanowire solar cells by off-axial core/shell design. (October 2015)

• Record Type: Journal Article
• Authors: Zhang, Cheng; Yang, Zhenhai; Shang, Aixue; Wu, Shaolong; Zhan, Yaohui; Li, Xiaofeng
• Is Part Of: Nano energy. Volume 17(2015:Oct.)
• Page Start: 233
• Page End: 240
• Publication Date: 2015-10
• Subjects: Photovoltaics -- Single-nanowire solar cells -- Light trapping -- Nanofocusing effect -- Optoelectronic simulation; Nanoscience -- Periodicals; Nanotechnology -- Periodicals; Nanostructured materials -- Periodicals; Power resources -- Technological innovations -- Periodicals; Nanoscience; Nanostructured materials; Nanotechnology; Power resources -- Technological innovations; Periodicals; 621.042
• DOI: 10.1016/j.nanoen.2015.08.017
• Languages: English
• ISSNs: 2211-2855

Abstract

Abstract: Single-nanowire solar cells (SNSCs) are attracting increasing interest due to their unique antenna-effect-mediated light-trapping and the efficient charge separation through thin semiconductor junctions. However, for such newly emerging photovoltaic devices, the optical and photoconversion performance is still far from the expectation. More effective strategies which are capable of providing broadband/high absorption and high electrical outcome are strongly desired. In this study, we introduce the concept of symmetry-breaking into the core/shell silicon SNSCs, which enables a substantially enhanced optical absorption under an improved coupling between the photoactive material and the focus of the dielectric shell. By properly deviating the silicon core away from the dielectric shell center (i.e., the off-axial core/shell design), the light-trapping capability of the device is significantly improved in almost the whole spectral band without degrading the carrier collection performance. Our optoelectronic simulation exhibits that the photocurrent density as well as the light-conversion efficiency of free-standing SNSCs can be doubled (enhanced by ~40%) compared to that of the system under bare (co-axial core/shell) nanowire design; moreover, the device performance under such asymmetric design can be further improved with introducing the metal-coated substrate. Graphical abstract: Absorption spectra of the bare, co-axial core/shell and off-axial core/shell Si SNSCs with Al-coated substrate under TE (a) and TM (b) normal incidences. Highlights: Asymmetrically configured core/shell Si SNSCs are reported. The new system exhibits substantially enhanced optoelectronic performance. The enhanced nanofocusing effect is responsible for the improved optical absorption. Both light-trapping and electrical performance has been evaluated.