ELECTRICAL CHARACTERIZATION OF a-Si(n+)/c-Si(p) HETEROJUNCTION SOLAR CELLS WITH BACK SURFACE PASSIVATION BASED ON a-SiC{sub}x: H FILMS

摘要

In this work, we report on the electrical characterization of solar cells based on amorphous/crystalline silicon heterojunctions (a-Si(n+)/c-Si(p)). Particularly, we fabricated solar cells using the so-called Heterojunction with Intrinsic Thin film (HIT) concept which consists in the deposition of a thin intrinsic a-Si:H film between the doped film and the c-Si substrate. Additionally, the back surface of the solar cells was passivated with amorphous silicon-carbide films (a-SiC{sub}x: H). The surface recombination rate was determined at different fabrication steps by means of effective lifetime (τ{sub}(eff)) vs. excess carrier density (Δn) curves measured by QSS-PC technique. Solar cell structures presented a much lower τ{sub}(eff) than expected from the dummy wafers used to controlled the surface passivation quality for both the HIT emitter and the a-SiC{sub}x: H film. Finished solar cells confirmed this poor result. Analysis of the dependence of current-voltage characteristic on temperature revealed high recombination at both surfaces most likely caused by a contamination during the photolithography step needed to define the point contact scheme for the back surface. Similar solar cells but with an Aluminium full-covered back surface (no photolithography) led to better results with a best efficiency of 14.3%.