Anomalous photoconductivity variations of solar cell quality a-Si:H thin films induced by proton irradiation

We investigated photoconductivity (PC) variations of hydrogenated amorphous silicon (a-Si:H) thin films irradiated with 0.10, 1.0 or 10 MeV protons. As a result, the PC values for all samples once increased and then decreased dramatically. Light-soaking treatment doesn´t affect the anomalous PC increment. In order to obtain the knowledge about the anomalous PC increment, dark current was monitored during and after 10 MeV proton irradiation. Radiation induced conductivity (RIC) and persistent excited conductivity (PEC) were clearly observed during and after the irradiation, respectively. Subsequently, the PC variations with time after 10 MeV proton irradiation at the fluence of 3.0×10¹³ /cm² were also investigated. The results showed that the PC value even after 270 hours was over twice higher than that before the irradiation, though the PC values decreased with time. However, the PC value became almost equivalent to the value before the proton irradiation by applying light-soaking. These results indicate that the anomalous PC increment is metastable.