LIGHT EMISSION AS A SOLAR CELL ANALYSIS TECHNIQUE.

Solar cells and light emitting diodes are similar devices. A solar cell, if under light, can charge a battery, while the battery in turn can cause the solar cell to emit light like an LED. Since the solar cell can be used as two separate devices, it can be used to test itself. Two types of light emission, forward bias and reverse bias, can be used to test the solar cell. Defects which are not readily apparent when examining the I-V curve (but can lead to device failure) can be detected using light emission. Two such common defects are irregularities at the junction and shunt defects. Both forward and reverse bias light emission can detect these types of shunts. Other, grosser defects are also readily apparent using light emission. These can include shunt defects, cracks, dirt, and an excessively thick collector. By examining the I-V characteristics of the solar cell, and the current density needed to begin light emission, localized information about the solar cell can be obtained and the type of defect can be determined.