Browsing by Author "Oyugi Ngure Robert"

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    Synthesis and characterization of silver sulphide-reduced graphene oxide nanocomposite for application in the photoactive and hole transport layers of organic solar cells
    (Egerton University, 2025) Oyugi Ngure Robert
    The demand for clean energy, occasioned by technological innovations, necessitates sustainable and cost-effective sources such as organic solar cells (OSCs), specifically bulk heterojunction polymer solar cells (BHPSCs). Inadequate light absorption and charge transport are the common challenges with these sources, which reduce their power conversion efficiency. Incorporating silver sulphide (Ag2S) and reduced graphene oxide (rGO) can improve light absorption and charge carrier mobility, respectively. The study reports successful synthesis, characterisation, and application of Ag;S-rGO nanocomposite (synthesised by chemical reduction method) to enhance the OSCs’ performance. Scanning electron microscopy (SEM) demonstrated the intercalation of rGO sheets within the Ag; S nanoparticles during the chemical reduction process, and that Ag2S had a nanowire shape. Further, SEM energy dispersive X-ray (SEM EDX) showed purity of Ag2S — rGO by indicating C, Ag, O, and S as the only elements in the nanocomposite. X-ray diffraction (XRD) analysis showed sharp and intense diffraction peaks, confinning the high crystallinity of the Ag2S nanoparticles. Thennal gravimetric analysis (TGA) showed rGO slowed nanocomposite decomposition between 520°C and 850°C. AgzS-rGO nanocomposite exhibited strong absorption of light in the ultraviolet and visible regions, making the nanocomposite suitable for use in OSCs. The Fourier Transform Infrared (FTIR) analysis of the nanocomposite showed strong AgzS-rGO interaction with new C-O-C and OH bands, indicating S1lCC€SSfLll integration of rGO into AggS, hence nanocomposite formation. The nanocomposite increased the light trapping of the P3HT: PCBM photoactive layer material within the visible region, improving the efficiency of OSCs in light harvesting. For the hole transport layers, however, the higher rGO content slightly reduced the light transmittance due to strong absorbance and plasmonic effects due to Ag2S nanoparticles. All the OSCs with modified active and hole transport layers (HTL) exhibited improved photovoltaic performance. The nanocomposite in the absorbing layer improved charge generation, leading to increased JSC (from 6.9 mAcm'2 to 17 mAcm'2) and a subsequent enhancement in PCE from 1.5% to 3.4% (a 127% increase). The nanocomposite improved charge collection at the interface, leading to an enhanced PCE by 53% (from 1.5% to 2.3%). The application of Ag2S-rGO nanocomposite considerably improved the performance of the OSCs after application in the HTL and the photoactive layers. Therefore, the study supports the development of sustainable energy solutions.