A microprocessor-based instrument for automatic solar cell characterization

A system which digitally records solar cell performance parameters is discussed and the design of a microcomputer based measurement system for solar cells is described. The key parameter is the current-voltage characteristic, assayed by sweeping the bias voltage to vary the cell output voltage from zero to the open circuit value at a load resistance which is varied to values of the ratio of the open circuit voltage and the short circuit current. Analog/digital and digital/analog conversion permits the interface of the microprocessor with an electronic load circuit. A system configured for the measurement includes a CPU running at 6.144 MHz, a programmable communication interface, a programmable interval timer, and the logic for buffering and driving the system bus. The operator is required to define the measurement modalities, the output data selection, and the cell selection criteria. Expansions into remote storage on a mainframe computer and continuous control of the light source are under investigation.