A Comparative Study on Synergy Between Energy Harvesting and Pressure Sensing in Piezotronic Heterojunctions

In this letter, a novel fully flexible piezotronic bipolar junction transistor (n-p-n PBJT) is designed and constructed by configuring two ZnO/Poly(3-hexylthiophene) heterojunction diodes back to back. The n-p-n PBJT acts as a signal-mediated device providing both current and voltage as the outputs. The utilization of the n-p-n PBJT in wearable applications is testified where a unique synergy between energy harvesting and sensing is found. Under mechanical stress, the output signal is amplified (with no preamplifier circuitry), which makes it a proper candidate as a high-performance sensor (voltage-based sensitivity is extracted as 0.49 V/kPa, four times higher than piezotronic p-n heterojunction). As a wearable energy harvester, the output signal is rectified (with no signal regulation circuitry), and it generates a peak output power of 2.9 µW, which is ten times higher than that of the piezotronic p-n diode. The outstanding performance of the n-p-n PBJT provides a new strategy to improve device performance for the emerging application in wearable electronics.