Activation energy E a values were extracted from linear Arrhenius plots by fitting the linear regression model using the least-squares method. Individual Arrhenius graphs are plotted in Figure and the resulting E a values are summarized in Figure . A noticeable feature in this system is the distinct hump in E a between the compositional range of x = 0.2 and 0.8. This trend may be attributed to multiple factors, including imperfect sample dimensions, in-gap defect states and variability in defect formation across different Te composition. For example, certain Te compositions may inherently favor more or fewer defects, which in turn can influence E a values. However, accurate quantification of defect concentrations across samples is not possible without a dedicated defect analysis, which was beyond the scope of this study. Due to these intrinsic complexities, E a is generally unreliable for accurate band gap estimation. Alternatively, optical measurements provide a more precise band gap approximation as they better represent bulk electron transport. The following section details diffuse reflectance studies conducted on Ag 3 Au(Se,Te) 2 .