Precise Surface State Control of Carbon Quantum Dots to Enhance Charge Extraction for Solar Cells

Qiming Yang,Peizhi Yang,Wen Yang,Yong Zhang,Wen Ge,Xin Yang

doi:10.3390/nano10030460

Abstract

Dye-sensitized solar cells are regarded as promising candidates to resolve the energy and environmental issues in recent years, arising from their solution-processable fabrication technology and high power conversion efficiency. However, there are still several problems regarding how to accelerate the development of this type of photovoltaics, including the limited light-harvesting ability and high-production cost of molecular dye. In the current work, we have systematically studied the role of nitrogen-doped carbon quantum dots (N-CQDs) as co-sensitizers in traditional dye sensitized solar cells. A series of N-CQDs have been prepared by employing chitosan as a precursor via one-pot hydrothermal technology for various times, demonstrating a maximized efficiency as high as 0.089% for an only N-CQDs-based device. Moreover, the co-sensitized solar cell based on N719 dye (C58H86N8O8RuS2) and optimized N-CQDs shows significantly enhanced performance, yielding a solar-to-electric conversion efficiency of up to 9.15% under one standard sun (AM 1.5G) irradiation, which is much higher than the 8.5%-efficiency of the controlled device without N-CQDs. The matched characteristics of energy level, excellent up-convention, and FRET (Förster resonance energy transfer) abilities of N-CQDs are responsible for their improved power conversion efficiency.

Highlights

In the past decades, dye-sensitized solar cells (DSSCs) have been considered as a novel alternative to silicon-based photovoltaics due to their low cost and relatively high conversion efficiency [1]
It is interesting that the coloration of the resultant nitrogen-doped carbon quantum dots (N-carbon quantum dots (CQDs)) solution is clearly observed in Figure 1a, suggesting an increased N-CQD concentration along with increasing the treatment time, which is mainly attributed to the formation of more nucleus and the growth of previously formed CQDs
The optimized of N-CQDs were characterized by comprehensive measurements, including TEM, X-ray diffraction (XRD), Raman, UV-Vis, Fourier Transform Infrared (FTIR), PL, and XPS

Summary

Introduction

Dye-sensitized solar cells (DSSCs) have been considered as a novel alternative to silicon-based photovoltaics due to their low cost and relatively high conversion efficiency [1].

Results

Conclusion