Impact of carrier doping on electrical properties of laser-induced liquid-phase-crystallized silicon thin films for solar cell application

Abstract

Large-grain-size (>1 mm) liquid-phase-crystallized silicon (LPC-Si) films with a wide range of carrier doping levels (10 16 -10 18 cm %3 either of the n-or p-type) were prepared by irradiating amorphous silicon with a line-shaped 804 nm laser, and characterized for solar cell applications. The LPC-Si films show high electron and hole mobilities with maximum values of >800 and >200 cm 2 V %1 s %1 , respectively, at a doping level of >(2-4) ' 10 16 cm %3 , while their carrier lifetime monotonically increases with decreasing carrier doping level. A grain-boundary charge-trapping model provides good fits to the measured mobility-carrier density relations, indicating that the potential barrier at the grain boundaries limits the carrier transport in the lowly doped films. The open-circuit voltage and short-circuit current density of test LPC-Si solar cells depend strongly on the doping level, peaking at (2-5) ' 10 16 cm %3 . These results indicate that the solar cell performance is governed by the minority carrier diffusion length for the highly doped films, while it is limited by majority carrier transport as well as by device design for the lowly doped films.

Assessment of Bulk and Interface Quality for Liquid Phase Crystallized Silicon on Glass

“…Absorber doping was achieved by subsequent PECVD deposition of an a-Si (n) layer using an adjusted phosphine flow rate. Cells with doping concentration (Nd) range of 10 16 cm -3 were investigated in this work since this doping range gives a good balance between Jsc and Voc [1], [17]. Samples were then capped with a PECVD SiOx layer and subsequently crystallized under vacuum conditions.…”