Solar Energy 208 (2020) 930–936 Available online 29 August 2020 0038-092X/© 2020 International Solar Energy Society. Published by Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Solar Energy journal homepage: www.elsevier.com/locate/solener Polycrystal metals nano-composite assisted photons harvesting in thin film organic solar cell Xolani Goodboy Mbuyise, Genene Tessema Mola ∗ School of Chemistry & Physics, University of KwaZulu-Natal, Pietermaritzburg Campus, Private Bag X01, Scottsville 3209, South Africa ARTICLE INFO Keywords: Tri-metallic nano-composite Nano-particles Thin film ABSTRACT Wet chemistry was employed to synthesis tri-metals nano-composite containing cerium, cobalt and calcium (Ce:Co:Ca). The optical and morphological properties exhibited by the synthesized nano-composite were found to be favourable for photovoltaic device applications. Consequently, the introduction of Ce:Co:Ca nano-particles in the P3HT:PCBM blend photo-active medium resulted in improved power conversion efficiency (PCE) by 104 % compared to the pristine active layer. The results unveil a new progress in achieving high overall solar cell performance through the use of triple metals composite local surface plasmon resonance (LSPR) effect and possible light trapping mechanism in the absorber layer. Furthermore, it was noted from the investigation that device performance is dependent on the particles concentration which was varied from 0 % to 3 % by weight. The optimum NPs concentration for the best power conversion efficiency was 3 wt% that produced a PCE of 5.3 % which is an important development for open-air device preparation condition. The metals nano-particles were studied using various spectrometers such as high-resolution scanning and tunnelling electron microscopy (HRSEM and HRTEM); energy dispersion X-ray (EDX); and X-ray diffraction (XRD) etc. All results are clearly presented and discussed in the manuscript. 1. Introduction Thin film solar cell technologies have attracted significant research attention in recent years because of their potential to mitigate the challenges to satisfy the growing demand for more energy. Particularly, the use of organic molecules as a medium to collect solar energy has been under intense investigation in the past two decades in an effort to produce cheap, light weight and flexible thin film organic solar cells (TFOSC) (Ranganathan et al., 2015). The introduction of bulk hetero- junction (BHJ) device architecture by Sariciftci et al. has drastically improved the progress towards achieving high performing organic solar cells. The BHJ medium consists of a mixture of electron-donor and electron-acceptor molecules generating nano-scale donor–acceptor (D– A) interfaces, which offers large surface area for charge dissociation within the active medium (Cui1 et al., 2019; Mola et al., 2017; Li et al., 2012). The best power conversion efficiency recorded from BHJ thin film organic solar cells currently stands over 16%. For the past few years, multifarious investigation have been conducted to improve the power conversion efficiency of TFOSC, in terms of engineering the synthesis of low-bandgap conjugated polymers (Jo et al., 2009; He et al., 2020; Dou et al., 2013), control of film morphology, interface engineering (Ye et al., 2012; He et al., 2011; Yin et al., 2020) and device fabrication processes (Wang et al., 2018a). ∗ Corresponding author. E-mail address: mola@ukzn.ac.za (G.T. Mola). To date, the incorporations of various dopant/additives such graphene, carbon nanotubes, solvent additives and metal nano- composites have influenced the device performance for the better. Especially, low temperature synthesized metal nano-particles exhib- ited important characteristic suitable for photonic device applications. Noble metals such as gold (Au), silver (Ag), copper (Cu) possess excellent optical and electrical properties that can be utilized as a mechanism to improve photons harvesting as well as charge transport processes (Hao et al., 2017; Deibel and Dyakonov, 2010; Blom et al., 2007; Su et al., 2012; Banerjee et al., 2014; Koutavarapu et al., 2020). This article reports on the facile synthesis of the Ce:Co:Ca nano- composite and it effects the performance thin film organic solar cell. The tri-metallic nanocomposite contains high opto-electronic properties and is compatible with roll-to roll device fabrications. These metals nanoparticles (NPs) contain comparable chemical properties and are known as transition metals. Particularly, Cerium is the very rare earth element of the lanthanide class in the Earth’s crust and is available at an amount of 66 ppm as a delocalized metal and/or metal oxide. It is one of the most important element that is commonly used in the field of metallurgy, ceramics, smart glass as well as in optics (Zamiri et al., 2015). The facile synthesis of Ce nano-particles makes it more https://doi.org/10.1016/j.solener.2020.08.048 Received 13 July 2020; Received in revised form 8 August 2020; Accepted 17 August 2020