Understanding the Strong Apparent Injection Dependence of Carrier Lifetimes in Doped Polycrystalline Silicon Passivated Wafers

Abstract

This study investigates the injection dependence of carrier lifetimes of p‐ and n‐type samples passivated by doped‐polycrystalline silicon (poly‐Si) (p+ and n+ poly‐Si) contacts. A strong apparent injection dependence of the carrier lifetimes is observed in p‐n junction samples (p+ poly‐Si on n‐type or n+ poly‐Si on p‐type) but no injection dependence is observed in high‐low junction samples (p+ poly‐Si on p‐type or n+ poly‐Si on n‐type). Further, photoluminescence images captured at two illumination intensities of 0.05 and 0.87 suns reveal that edge recombination contributed the strong apparent injection dependence in p‐n junction samples. Furthermore, this apparent injection dependence increases as the sample size is reduced, and as the sheet resistance of the doped poly‐Si contacts is decreased, allowing more effective transport of minority carriers to the recombination‐active edge regions.