On the evaluation of output voltages for quantifying the performance of pyroelectric energy harvesters

Pyroelectric energy harvesters (PyEHs) have been extensively developed for the energy supply to wireless, low-power advanced devices. Plenty of experiments show that the voltage–time curves for evaluating pyroelectric devices are alternatively positive and negative, while the fundamental pyroelectric theory gives a positive voltage without the negative portion. Here, this key confliction is addressed by both theoretical and experimental investigation. The voltage-time curves are recorded by three voltmeters with inner resistances of 10 MΩ, 150 GΩ, and 200 TΩ, respectively. Measured output voltages are found to be influenced greatly by the voltmeter's resistance and capacitance, with peak voltages differing by a factor that exceeds 2200. The performance of the PyEH should be characterized by the intrinsic voltage rather than the open-circuit voltage. As a significant conclusion, the resistance and capacitance of voltmeters used should be reported in the literature, thus providing a rationale for comparing the performance of different devices.