Role of silicon surface, polished 〈100〉 and 〈111〉 or textured, on the efficiency of double‐sided TOPCon solar cells

Abstract We investigate the role of the silicon surface and orientation on double‐sided TOPCon solar cells properties. The solar cells of front and rear, (p) and (n), poly‐Si/SiO x stack, fabricated on polished surfaces oriented 〈100〉 and 〈111〉 and pyramid textured surfaces, are characterized as a function of the thickness of an ultrathin SiO x layer, controlled at atomic scale from one‐ to four‐cycle atomic layer deposition (ALD). Our findings underline that the optimized thickness of the ultrathin SiO x is about 1.1 ± 0.1 nm, corresponding to a two‐cycle ALD, regardless of the surface and orientation of the c‐Si substrate. The open‐circuit voltage is about 10 mV higher on the polished 〈100〉‐oriented surface, associated with lower defect density at the interface of SiO x /c‐Si. On the other hand, the contact resistance is much lower, about 0.45 Ω/cm 2 , on the polished 〈111〉‐oriented surface. On textured surfaces, we demonstrate a photoconversion efficiency of 19.1% for the double‐sided TOPCon structure strictly for a SiO x thickness with two‐cycle ALD, which underlines the importance of the ALD technique for the precise control of the ultrathin SiO x thickness on textured surface.