Shi Jinchao

Application of minority carrier lifetime monitor in heterojunction solar cell production

Heterojunction solar cell is one of the high efficiency crystalline Si solar cell that have implemented large volume production. Development of a simple and effective monitoring scheme is the premise of mass production. To monitor the quality of thin films and track the solar cell performance, effective minority carrier lifetimes of a-Si:H(i)/c-Si/a-Si:H(i), a-Si:H(p+)/a-Si:H(i)/c-Si/a-Si:H(i)/a-Si:H(n+) and TCO/a-Si:H(p+)/a-Si:H(i)/c-Si/a-Si:H(i)/a-Si:H(n+) structures were measured during process. It was shown that implied Voc and pFF were improved with the increasing of effective minority carrier lifetime till ~2 ms and then saturated, which could be explained that the Fermi level difference tends to maximum value along with decreasing of surface recommendation in Si under non-equilibrium state. By tracking the minority carrier lifetime, it is possible to analyze the performance of the a-Si:H(i) films and the influence of ion bombardment on a-Si:H(i) films in the process of TCO deposition, and could predict the performance of heterojunction solar cells and monitor the stability and anomalies in production line.