ABSTRACT
Improving electrical and optical properties is important in manufacturing high-efficiency solar cells. Previous studies focused on individual gettering and texturing methods to improve solar cell material quality and reduce reflection loss, respectively. This study presents a novel method called saw damage gettering with texturing that effectively combines both methods for multicrystalline silicon (mc-Si) wafers manufactured using the diamond wire sawing (DWS) method. Although mc-Si is not the Si material currently used in photovoltaic products, the applicability of this method using the mc-Si wafers as it contains all grain orientations is demonstrated. It utilizes saw damage sites on the wafer surfaces for gettering metal impurities during annealing. Additionally, it can crystallize amorphous silicon on wafer surfaces generated during the sawing process to allow conventional acid-based wet texturing. This texturing method and annealing for 10 min allow for the removal of metal impurities and effectively forms a textured DWS Si wafer. The results show that the open-circuit voltage (ΔVoc = +29 mV), short-circuit current density (ΔJsc = +2.5 mA cm-2 ), and efficiency (Δη = +2.1%) improved in the p-type passivated emitter and rear cells (p-PERC) manufactured using this novel method, as compared to those in the reference solar cells.
ABSTRACT
In this paper we present a contactless transient carrier spectroscopy and imaging technique for traps in silicon. At each pixel, we fit the transient decay of the trap emission which allows us to obtain both the trap time constant and trap concentration. Here we show that this technique allows for high-resolution images. Furthermore, this technique also allows to discriminate between the presence of thermal donors or oxygen precipitates in as-grown wafers, without requiring a thermal donor killing step.
