Optimization of segmented solar thermoelectric generator for power output enhancement has been well researched however, the mechanical reliability study of such devices is usually neglected. In addition, assumed heat flux distribution or uniform flux distribution from solar concentrators is usually used for solar thermoelectric generator however, this is not accurate. Therefore, this study presents a detailed three-dimensional numerical investigation on the effect of non-uniform and uniform heat flux on the electrical and mechanical performance of segmented and non-segmented solar thermoelectric generator. Flux distribution from a compound parabolic concentrator is obtained by ray tracing using Lighttools software and COMSOL 5.4 Multiphysics software is used to perform the numerical study based on finite element method. Thermal stress analysis in a full-scale solar thermoelectric generator is presented and the effects of load resistance, solar radiation and cold side temperature on performance of solar thermoelectric generator is analysed. Results show that the power output of the segmented solar thermoelectric generators in Case 3, Case 4 and Case 5 increased by 44.07%, 59.12% and 37.9% respectively compared to that of Case 1 (bismuth telluride non-segmented solar TEG) at 13000W/m2. Results from this study will provide valuable guidance for segmented and non-segmented solar thermoelectric generator design.