Gold nanoparticles (Au NPs) were synthesized via a green synthesis method, utilizing the peel extract of Artocarpus odoratissimus as both the reducing and capping agent. This study investigates the impact of peel extract concentration (ranging from 0.002 to 0.012 g/mL) and reaction temperature (including room temperature, 45 °C, and 75 °C) on the properties of the synthesized Au NPs. Various characterization techniques, such as UV–Visible spectrophotometry, transmission electron microscopy (TEM), Fourier Transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), and zeta potential analysis, were employed to analyze the synthesized samples. UV–Visible spectroscopy revealed absorption peaks of the Au NPs around 533–537 nm, varying with synthesis parameters, while TEM analysis indicated particle sizes ranging from 12 to 25 nm. XRD analysis confirmed the formation of Au NPs, with diffraction peaks aligning well with the standard. FTIR analysis suggested interactions between phytochemicals and Au NPs, contributing to their reduction and size control. The synthesized Au NPs exhibited remarkable optical filtering capability, with up to 87 % transmittance in the 751–1126 nm spectral range and significant absorbance in the lower wavelength region (300–751 nm). Additionally, catalytic studies revealed that Au NPs accelerated the degradation of rhodamine B dye, 0.0795 min−1, compared to 0.0445 min−1 without Au NPs. These findings underscore the potential of Au NPs for use in hybrid photovoltaic-thermal systems as filters, where transmitted light can be harvested for photovoltaic energy generation while absorbed light can be utilized for the thermal aspect. Moreover, Au NPs offer promise for improving wastewater quality by enhancing pollutant degradation.