Tube‐type plasma‐enhanced atomic layer deposition of aluminum oxide: Enabling record lab performance for the industry with demonstrated cell efficiencies >24%

Abstract

In this work, single-side aluminum oxide (Al 2 O 3 ) deposition enabled by a new tubetype industrial plasma-assisted atomic layer deposition (PEALD) technique is presented to meet the increasingly stringent requirements for high-efficiency solar cell mass production. Extremely low emitter saturation current densities, J 0e , down to 15 fA/cm 2 are achieved on an industrial textured boron emitter with a sheet resistance of 104 Ω/sq, passivated by PEALD Al 2 O 3 /PECVD SiN x stack after firing. An implied open-circuit voltage of up to 721 mV is obtained on symmetrical lifetime samples. The underlying passivation mechanisms of this new tube-type PEALD Al 2 O 3 are investigated by contactless corona-voltage measurements. The results indicatethat the superior passivation is mainly attributed to a low interface defect density down to 1.1 Â 10 11 cm À2 eV À1 and a high negative fixed charge density up to 4.5 Â 10 12 cm À2 . Simulations show that the obtained J 0e is close to its intrinsic limit.Lastly, the developed tube-type PEALD Al 2 O 3 is applied to industrial TOPCon solar cells achieving an average cell efficiency above 24% and a maximum V oc of 707 mV.This work shows that the record level of surface passivation available from lab-scale PEALD reactors is now available in a flexible high-throughput industrial PEALD platform, which opens a new route for mass production of high-efficiency industrial TOPCon solar cells with a lean process at low costs.