Synthesis of N,S-Doped Carbon Quantum Dots for Use in Organic Solar Cells as the ZnO Modifier To Eliminate the Light-Soaking Effect

Abstract

Zinc oxide (ZnO) is one of the most extensively used electron-transporting layers (ETLs) in organic solar cells. However, owing to numerous surface defects and mismatched energy bands with the photoactive layer, light-soaking process is usually required to achieve a high device performance for the ZnO-based cells. Herein, we reported the synthesis of N,S-doped carbon quantum dots (N,S-CQDs) by a simple hydrothermal treatment using ascorbic acid and ammonium persulfate as reagents. As characterized by high-resolution transmission electron microscopy and X-ray diffraction, the synthesized CQDs were found to be 2−7 nm in dimensions, having a graphite-structured core and amorphous carbon on the shell. Fourier transform infrared and X-ray photoelectron spectroscopy analyses confirmed that these CQDs are highly nitrogen-and sulfur-doped, which leads to efficient (with a quantum yield of 33%) downconversion and excitation-dependent photoluminescence character. Application of these N,S-CQDs as surface modifier for ZnO layer in inverted organic solar cells was investigated. Results indicate that the cells with N,S-CQDs-decorated ZnO ETL showed higher power conversion efficiency without S-shaped kink in the current density−voltage curves. The performance improvement and the elimination of light-soaking effect for ZnO:N,S-CQDs cells are attributed to the ZnO surface defect passivation by N,S-CQDs, as confirmed by fluorescence spectroscopy and scanning Kelvin probe microscopy. The cells with N,S-CQDs-modified ZnO ETL showed a high power conversion efficiency of 9.31%, which is higher than the reference ZnO cells. The current work provides a feasible way to achieve shell element-doped CQDs for specific application in organic electronic devices.

Sulfate Surfactant Assisted Approach to Fabricate Sulphur‐Doped Supported Nanodiamond Catalyst on Carbon Nanotube with Unprecedented Catalysis for Ethylbenzene Dehydrogenation

“…Owing to the high specific surface area of the samples, they may adsorb the H 2 O in air, which results in the H 2 O peak at 536.1 eV in the spectra. And the SO 4 2− peak also about at the 536.5 eV . From Table S2, the ND/CNT‐SDS shows much higher surface C=O content than the pristine ND.…”

“…And the SO 4 2À peak also about at the 536.5 eV. [48] From Table S2, the ND/CNT-SDS shows much higher surface C=O content than the pristine ND. The supported-type ND/CNT catalyst without the dispersion of ND or CNT (1.0 at% C=O) shows slightly higher surface C=O percentage to the CNT (0.6 at% C=O) and ND (0.4 at% C=O), originating from the poor dispersion of ND and CNT.…”

Passivating Surface Defects of n‐SnO2 Electron Transporting Layer by InP/ZnS Quantum Dots: Toward Efficient and Stable Organic Solar Cells

“…Besides above materials, the utilization of quantum dots (QDs) as an interfacial modifier to form QDs/ETL bilayer in OSCs has received more attention 26,27. With the advantages of good water/alcohol solubility, diversity of nanostructure, and size, as well as the tunable optical and electrical properties, the QDs/ETL bilayers have been widely used in optoelectronic devices 28–30. Furthermore, the integral absorption enhancement was observed in OSCs by introducing QDs in the photovoltaic matrix, due to their unique performance of luminescence emission 26.…”

Application of carbon dots in dye‐sensitized solar cells: A review

“…As mentioned above, doping is a significant way to control the properties of nanomaterials, different surface functionalization also has a notable influence on the sensitization effect of CDs in cells . It is well documented that heteroatom doping (i.e., N, S, F, Si, B 60 ) can enhance CDs optical properties and collection of the more solar spectrum.…”

“…Due to superior intrinsic catalytic activity, GQDs were decorated to PPy on fluorinated tin oxide (FTO) glass as a highly efficient but inexpensive CE for high‐performance DSSCs . Similarly, GQDs were also doped onto SrRuO 3 CE by dipping technique to form a hybrid CE . The synergistic effect of SrRuO 3 and GQDs leads to more active catalytic sites as well as faster ion diffusion and electron transfer than pristine SrRuO 3 ‐CE.…”