Nanomaterials 2022, 12, 3409. https://doi.org/10.3390/nano12193409 www.mdpi.com/journal/nanomaterials Article Roles of TOPO Coordinating Solvent on Prepared Nano-Flower/Star and Nano-Rods Nickel Sulphides for Solar Cells Applications Mojeed A. Agoro 1,2, * and Edson L. Meyer 1 1 Fort Hare Institute of Technology, University of Fort Hare, Private Bag X1314, Alice 5700, South Africa 2 Department of Chemistry, University of Fort Hare, Private Bag X1314, Alice 5700, South Africa * Correspondence: magoro@ufh.ac.za or amodoyin@gmail.com; Tel.: +27-781246437 Abstract: The present study describes a cheap, safe, and stable chemical process for the formation of nickel sulphide (NiS) with the use of mixed and single molecular precursors. The production pathway is uncomplicated, energy-efficient, quick, and toxic-free, with large-scale commercializa- tion potential. The obtained results show the effect of tri-N-octylphosphine oxide (TOPO) as a coor- dinating solvent on the reaction chemistry, size distributions, morphology, and optical properties of both precursors. Ni[N,N-benz-N-p-anisldtc] as NiSa, Ni[N,N-benzldtc] as NiSb, and Ni[N-p-ani- sldtc] as NiSc thermally decompose in a single step at 333–334 °C. The X-ray diffraction peaks for NiSa, NiSb, and NiSc matched well with the cubic NiS nanoparticles and corresponded to planes of (111), (220), and (311). The extrapolated linear part from the Tauc plots reveals band gap values of 3.12 eV, 2.95 eV, and 2.5 eV, which confirms the three samples as potential materials for solar cell applications. The transmission electron microscopy (TEM) technique affirmed the quantum dot size distribution at 19.69–28.19 nm for NISa, 9.08–16.63 nm for NISb, and 9.37–10.49 nm for NISc, respec- tively. NiSa and NiSc show a clearly distinguishable flower/star like morphology, while NiSb dis- plays a compact nano-rod shape. To the best of the authors’ knowledge, very few studies have been reported on the flower/star like and nano-rod shapes, but none with the dithiocarbamate molecular precursor for NiS nanoparticles. Keywords: molecular precursor; nickel sulphide; quantum dots; particles size; morphology 1. Introduction The current situation between Russia and most of the developed western countries, namely their sore dependence on Russian coal, fuels, and gas products, is having a serious impact on their economies. The only possible solution to these geometrical political con- straints is a change to a renewable energy that is cost-effective, easy to generate, and en- vironmentally friendly, such as solar energy. The most promising next-generation solar cells in the last two decades have been quantum dot-sensitized solar cells (QDSCs), which have reasonable efficiency and future-enhancement prospects. These future expectations are linked to their ability to optimize quantum dots (QDs) particle sizes, their cost friend- liness, easy fabrication, and different wavelength ranges that will cover the visible light spectrum. Furthermore, a single photon can greatly enhance the conversion output of QDSCs through multiple-exciton excitons, making QDs a potential candidate in applica- tions, such as solar cells [1–7]. Replacing the dye molecules in the dye-sensitized solar cell structure principle with QD semiconductors will increase conversion efficiency [8–10]. QDs semiconductors from metal chalcogenides (selenides, sulphides, tellurides) have been employed in QDSCs as photosensitizers, displaying remarkable performance, as well as in other applications such as optical conductors, IR detectors, coatings, and many more [11,12]. Nickel sulphide (NiS) has a phase structure that is more intricate than Citation: Agoro, M.A.; Meyer, E.L. Roles of TOPO Coordinating Solvent on Prepared Nano-Flower/Star and Nano-Rods Nickel Sulphides for Solar Cells Applications. Nanomaterials 2022, 12, 3409. https:// doi.org/10.3390/nano12193409 Academic Editors: Baizeng Fang and Efrat Lifshitz Received: 3 September 2022 Accepted: 27 September 2022 Published: 28 September 2022 Publisher’s Note: MDPI stays neu- tral with regard to jurisdictional claims in published maps and institu- tional affiliations. Copyright: © 2022 by the authors. Li- censee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and con- ditions of the Creative Commons At- tribution (CC BY) license (http://crea- tivecommons.org/licenses/by/4.0/).