Results and Discussion
In this study, we consider Z2 (Fig. 1(a)) as two parameters in parallel (Fig. 1(b)), i.e. diode resistance
(R2) and diode capacitance (C2). Under dark condition, looking at an output port, we can model the
photovoltaic impedance (ZPV) as consisting of a resistive and a reactive component in series in the form of
RPV + jXPV. At each bias voltage (V) and signal frequency (ω), the impedance can be expressed as
equation (1).
For simplification, we drop V and ω, and lump Rsh and R2 (Rsh//R2) into parallel resistance (RP). The
simplified dynamic impedance equation can be rewritten as equation (2).
It should be noted that C2 are voltage and frequency dependent, and R2 is voltage dependent [1-2].
Dynamic impedances under both forward and reverse biases at 0.2, 0.3, and 0.4 V are determined by
FRA under dark conditions. Impedance loci are plotted in a complex plane as shown in Fig. 2. It is found
that, the impedance loci are semicircles and conform to equation (2). At high and low frequencies for