Purpose <p>The rapid accumulation of Internet of Things (IoT) demands high performance energy harvesters for autonomous wireless sensors. In today’s practical applications, piezoelectric devices are a key area of focus for enhancing output and sensitivity for energy harvesting in IoT applications.</p> Methods <p>This study focuses on modifying the geometric configurations of the cantilever beam model by incorporating various piezoelectric cellular structures, such as honeycomb, and square cellular structures, additionally cavity-integrated structures for both honeycomb and square structures. Using Finite Element Analysis (FEA), a stationary and frequency-based energy harvesting analysis is performed to evaluate the electrical response of the introduced geometries. Furthermore, cavity-induced neutral-axis redistribution and topology-driven strain amplification enhance electromechanical performance is explored.</p> Results <p>Across all structural types, the inclusion of cavities significantly improved performance metrics in both voltage and power output. The stationary results revealed that the honeycomb cavity structure achieved the highest output voltage, followed by square and plane structures. In frequency-based energy harvesting analysis, the cavity-based honeycomb design significantly generates high output voltage and power at lower resonant frequency. The honeycomb cavity structure emerged as the optimal design by lowering resonant frequency 223.2 Hz for efficient low frequency harvesting. Significantly, this topology achieved 2.6 times increase in power output of 1.59 mW compared to the regular without cavity design. Moreover, normalizing by effective piezoelectric volume revealed 45 times enhancement in active volumetric power density of 473.84 𝜇𝑊⁄𝑚𝑚3 relative to regular plane structure.</p> Conclusion <p>These geometric findings are validating geometric optimization as vital strategy for developing compact, high-efficiency power sources for IoT applications.</p>