Macroscopic Study on Current Transport Path in Front‐Side Contacts of Crystalline Silicon Solar Cells

Abstract

Double rectangular transmission line model and contact‐end voltage measurement are used to study the variation in sheet resistance and current transfer length of the contact interface between the front‐side electrode and the emitter of crystalline silicon solar cells during metallization. The current distribution and its relationship with the sheet resistances of the electrode, contact interface, and emitter are given at the macrolevel. The model shows that the current flows transversely for ≈50–500 μm in the highly conductive interface with a sheet resistance in the range of 0.5–5 Ω □−1 beneath the designed electrodes. The I–V curves beneath the front silver pad sintered at lower, optimum, and over‐fired temperatures are always linear. However, they are nonlinear between the front‐side and rear‐side electrodes of the double phosphorus‐doped N‐type silicon substrates, which suggests that the contact type changes from Ohmic to Schottky. The experimental results imply that the photogenerated current on the emitter surface is mainly transferred transversely via the crystallites embedded in the shallow highly doped silicon layer rather than the deeper lightly doped contact area at the contact interface.