Measurement of built-in potential in polymorphous Si:H p-i-n solar cells

The performance of a solar cell, especially open-circuit voltage (Voc), is critically related to the built-in potential (Vb). In this work, the open-circuit voltage Voc and the short-circuit current density Jsc of hydrogenated polymorphous silicon (pm-Si:H) p-i-n solar cell, deposited by radio-frequency powered plasma-enhanced chemical vapour deposition (RF-PECVD), have been measured. From the measured data at different monochromatic illumination intensities and temperatures, the value of Vb of cell was determined by using two different methods: activation energy and differential temperature. The results from both methods were analyzed and compared as a function of excitation wavelength. It was observed that there is a good agreement between the two methods. It was found that Vb increases until about 650 nm, and then decreases with increasing wavelength. This behaviour is explained and interpreted in different ways