Impact of AlOx Capping Layer Thickness for Edge Passivation of TOPCon2 Shingle Solar Cell

Abstract

This work aims at understanding the short circuit current density losses observed on TOPCon² solar cells after AlO_x layer deposition and annealing. This process is the most considered for edge passivation of shingle solar cell, who suffer from heavy edge recombination losses after cutting procedures. Our solar cells feature Transparent Conductive Oxide (TCO) layers at the front and rear sides, on top of which the AlO_x edge passivation layer is deposited during Atomic Layer Deposition (ALD) process. We focus on the effect of the AlO_x layer thickness and the annealing conditions on the optical and electrical properties of the front AlO_x/TCO stack. It is found that annealing of thick AlO_x layers induce an increase of free carriers’ concentration in the TCO layer, resulting in additional parasitic absorption. Thinner AlO_x layer and/or cooler annealing condition would limit this phenomenon, however rising a compromise with the shingle edge passivation goal. Indeed, we see that applicated on the TOPCon² shingle solar cells, less current density loss comes along lower edge passivation level.