Enhanced Photosensitization by Carbon Dots Co-adsorbing with Dye on p-Type Semiconductor (Nickel Oxide) Solar Cells

Abstract

In this work, the effect of carbon dots (C-dots) on the performance of NiO-based dye-sensitized solar cells (DSSCs) was explored. NiO nanoparticles (NPs) with a rectangular shape (average size: 11.4 × 16.5 nm2) were mixed with C-dots, which were synthesized from citric acid (CA) and ethylenediamine (EDA). A photocathode consisting of a composite of C-dots with NiO NPs (NiO@C-dots) was then used to measure the photovoltaic performance of a DSSC. A power conversion efficiency (PCE) of 9.85% (430 nm LED@50 mW/cm2) was achieved by a DSSC fabricated via the adsorption of N719 sensitizer with a C-dot content of 12.5 wt % at a 1.5:1 EDA/CA molar ratio. This PCE value was far larger than the PCE value (2.44 or 0.152%) obtained for a NiO DSSC prepared without the addition of C-dots or N719, respectively, indicating the synergetic effect by the co-adsorption of C-dots and N719. This synergetically higher PCE of the NiO@C-dot-based DSSC was due to the larger amount of sensitizer adsorbed onto the composites with a larger specific surface area and the faster charge transfer in the NiO@C-dot working electrode. In addition, the C-dots bound to the NiO NPs shorten the band gap of the NiO NPs due to energy transfer and give rise to faster charge separation in the electrode. The most important fact is that C-dots are the main sensitizer, while N719 tightly adsorbs on C-dots and NiO behaves as an accelerator of a positive electron transfer and a restrainer of the electron–hole recombination. These results reveal that C-dots are a remarkable enhancer for NiO NPs in DSSCs and that NiO@C-dots are promising photovoltaic electrode materials for DSSCs.

Effects of Heteroatom Doping of Carbon Dots from Sugar on Optical Properties, Phenolic Content, Antioxidant Activity, Photostability, and Cytotoxicity

“…This is believed to be due to the Burstein‐Moss shifts. The chemical potential in the conduction band is pointing upward, which results in occupied states close to the band edge, leading to a wider band gap for heteroatom‐doped CDs [28–30] …”

Hybridization of nickel oxide nanoparticles with carbon dots and its application for antibacterial activities

“…[27] As previously reported, the NiO NPs were cubic in structure and their composites with carbon dots crystallized in a similar crystal structure (Figure 1a,b). [26] As revealed from Figure 1 Most of the constituent particles have a cubic shape, as illustrated using TEM surface morphology (Figure 1a,b). When the image is displayed, there a ruler in the TEM software that was used to measure each particle size.…”

“…[ 26 ] The composite of carbon dots with NiO NPs was also prepared according to a previously reported method and procedure. [ 26 ]…”

“…The carbon dots were synthesized from benzene‐1,4‐diamine and CA according to a previously reported method and procedure. [ 26 ] The composite of carbon dots with NiO NPs was also prepared according to a previously reported method and procedure. [ 26 ]…”

Luminescent Metal–Organic Frameworks for White LEDs

“…As two important members of the carbon family, graphene and luminescent carbon materials have caught tremendous attention these years on account of their unique electrical, optical and mechanical properties. [43] Carbon dots (CDs) have been extensively explored in many fields including photovoltaic devices, [44] light emitting diodes, [45] photodetectors, [46] photocatalysis [47] and lithium ion batteries, [48] on the merits of nontoxicity, favorable biocompatibility, low cost, outstanding chemical/optical stability. [49] Nevertheless, severe aggregation-caused self-quenching remains as the main drawback for solid-state CDs, which is attributed to the inside π-π interaction and resonance energy transfer, similar with the condition of organic dyes.…”