Lifetime Spectroscopy Investigation of Light-Induced Degradation in p-type Multicrystalline Silicon PERC

When untreated, light-induced degradation (LID) of p-type multicrystalline silicon (mc-Si)-based passivated emitter and rear cell (PERC) modules can reduce power output by up to 10% relative during sun-soaking under open-circuit conditions. Identifying the root cause of this form of LID has been the subject of several recent investigations. Lifetime spectroscopy analysis, including both injection and temperature dependencies (IDLS and TIDLS), may offer insight into the root-cause defect(s). In this paper, to illustrate the root-case defect identification method, we apply room-temperature IDLS to intentionally Cr-contaminated mc-Si. Then, we apply this technique to the p-type mc-Si that exhibits LID in PERC devices, and we provide further insights by analyzing qualitatively the injection-dependent lifetime as a function of temperature. We quantify the sensitivity of the capture cross-section ratio to variations in the measured lifetime curve and in the surface recombination. We find that the responsible defect most likely has an energy level between 0.3 and 0.7 eV above the valence band and a capture cross-section ratio between 26 and 36. Additionally, we calculate the concentrations of several candidate impurities that may cause the degradation.