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

Abstract

AbstractIn this work, single‐side aluminum oxide (Al2O3) deposition enabled by a new tube‐type 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, J0e, down to 15 fA/cm2 are achieved on an industrial textured boron emitter with a sheet resistance of 104 Ω/sq, passivated by PEALD Al2O3/PECVD SiNx 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 Al2O3 are investigated by contactless corona‐voltage measurements. The results indicate that the superior passivation is mainly attributed to a low interface defect density down to 1.1 × 1011 cm−2 eV−1 and a high negative fixed charge density up to 4.5 × 1012 cm−2. Simulations show that the obtained J0e is close to its intrinsic limit. Lastly, the developed tube‐type PEALD Al2O3 is applied to industrial TOPCon solar cells achieving an average cell efficiency above 24% and a maximum Voc 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.