No abstract

Molecular beam epitaxy (MBE) grown Cu(In 1%x ,Ga x )Se 2 (CIGS) thin films were sulfurized at temperatures of 450-550 °C for 30 min in a 10% H 2 S-N 2 mixture gas. The micro-roughness together with the S diffusion in the CIGS surfaces increased with increasing sulfurization temperature. Both near-band-edge PL intensity and decay time of the CIGS absorber layer enhanced after sulfurization. PL sub-peak around 80 meV below the main peak almost disappeared after sulfurization above 500 °C, which is expected due to the occupation of Se vacancies (V se ) with S. The open-circuit voltage (V oc ), hence conversion efficiency, improved after sulfurization. The photovoltaic performance of the solar cells was consistent with PL intensity. Moreover, it is found for the first time from the SIMS analysis that the Cu atoms were depleted at the surface of CIGS layer after sulfurization, which could result in the improved V oc .

We have studied the effect of geometry on the trapped magnetic field in bulk Y–Ba–Cu–O superconductors by varying the thickness. The trapped field first increased with increasing thickness of the bulk superconductor, and then saturated when the thickness reached a certain value. We have also performed simulation studies based on the sand-pile model and the Biot–Savart law, which were in fairly good agreement with the experimental results.

No abstract