Probing hidden conduction mechanisms in diced silicon solar cells by low frequency noise analysis

Abstract

Electrical low frequency noise (LFN) measurements are utilized in this work, in order to identify parasitic low voltage transport mechanisms in diced aluminum back surface field (Al-BSF) photovoltaic (PV) cells, which cannot be identified by I–V characterization. A detailed method of LFN analysis is proposed, taking into account the co-existence of various transport mechanisms, that typically occur in parallel in such devices. A precise examination of the 1/f noise level dependency with both current and voltage, combined with static I–V characterizations at various temperatures, enabled the identification of two flicker noise sources appearing at different current regions: one attributed to local linear shunt mechanisms and a second one to a fluctuation in a nonlinear parasitic conductivity localized at the samples’ edges. The latter source exhibits noise signatures resembling either tunneling or Poole-Frenkel transport, while excluding Shockley-Read-Hall recombination processes. This hypothesis was further verified by measurements of thermal activation energies typical of tunnel and Poole-Frenkel conduction mechanisms.