Solar Cell VoltageCurrent Characterization（太阳能电池VoltageCurrent表征）.pdfVIP

Solar Cell Voltage – Current Characterization Introduction A solar cell is a semiconductor PN junction diode, normally without an external bias, that provides electrical power to a load when illuminated (Figure 1). Sunlight + P Load N _ Figure 1. The basic solar cell structure. Typical voltage-current characteristics, known as the IV curve, of a diode without illumination is shown in green in Figure 2. The applied potential is in the forward bias direction. The curve shows the turn-on and the buildup of the forward bias current in the diode. Without illumination, no current flows through the diode unless there is external potential applied. With incident sunlight, the IV curve shifts up and indicates that there is external current flow from the solar cell to a passive load. I More Light V Dark Figure 2. The progression of the solar cell IV curve as the incident light increases. Short circuit current, Isc , flows with zero external resistance (V= 0) and is the maximum current delivered by the solar cell at any illumination level. Similarly, the open circuit voltage, Voc, is the potential that develops across the terminals of the solar cell when the external load resistance is very large (Figure 3). The power delivered to the load is of course zero at both extremes and reaches a maximum (Pmax) at a finite load