The output power of the PV cell is voltage times current, so there is no output power for a short-circuit condition because of VOUT or for an open-circuit condition because of IOUT = 0. Above the short-circuit point, the PV cell operates with a resistive load.
(Image courtesy of Advanced Photonix, Inc., advancedphotonix.com.) (Middle) Circuit symbol for a photocell. (Right) A simple light-level-detection circuit. In bright light, the photocell’s resistance is around 10 kΩ, making an output of about 2.7 V. In darkness, the photocell’s resistance is around 500 kΩ, making an output of about 0.3 V.
A photocell is a resistor that changes resistance depending on the amount of light incident on it. A photocell operates on semiconductor photoconductivity: the energy of photons hitting the semiconductor frees electrons to flow, decreasing the resistance. An example photocell is the Advanced Photonix PDV-P5002, shown in Figure 21.2.
The light-activated photocell circuits in Figs. 5 to 10 all have relay outputs that can control many different kinds of external circuits. In many light-activated circuit applications, however, the circuits must trigger audible alarms. This response can also be obtained without relays as shown in Figs. 11 to 17.
In bright light, the photocell’s resistance is around 10 kΩ, making an output of about 2.7 V. In darkness, the photocell’s resistance is around 500 kΩ, making an output of about 0.3 V. The sensor output could go to a PIC32 digital or analog input. Kevin M. Lynch, ... Matthew L. Elwin, in Embedded Computing in C with the PIC32 Microcontroller, 2016
Our efficiency calculations, based on Eq. 14.28, use a very simple model that totally ignores the photocell itself which is assumed to be 100% efficient. Its results are identical to the ultimate efficiency of Shockley and Queiser (SQ).
The resistance of the photocell is high in the second example, and then the circuit lane will change. So the low resistance to the base of the transistor or through the photocell would be there. Whenever the transistor''s base terminal gets power, then the transistor 2N222A …