Nitrogen-Incorporated Silicon Dioxide Interlayer Enables Pinhole-Reduced and Robust TOPCon With a High Implied Open-Circuit Voltage over 760 mV.

Abstract

Tunnel oxide passivating contact (TOPCon) technology has emerged as an industrial cornerstone for high-efficiency crystalline silicon (c-Si) solar cells. However, its passivation performance remains constrained by the thermal fragility of the ultrathin silicon dioxide (SiO_x) interface and the resulting formation of pinholes. Here, we report a nitrogen (N)-incorporated TOPCon structure in which nitrogen (N) atoms are in situ doped into amorphous silicon via plasma-enhanced chemical vapor deposition (PECVD) and are driven to the SiO_x during annealing to form a robust SiO_xN_y interlayer. First-principles calculations reveal that SiO_xN_y exhibits significantly enhanced bonding strength and superior thermal stability. Finite element simulations further show that SiO_xN_y possesses a thermal expansion coefficient better matched to both c-Si and poly-Si, suppressing stress concentration, preventing interface fracture, and reducing pinhole density. This atomic-scale modification enables record-breaking passivation performance, achieving an implied open-circuit voltage of 760 mV and a low single-sided recombination current density of 0.35 fA/cm². Device simulations predict that the efficiencies of various TOPCon-based cells can be significantly enhanced with minimal additional cost. Experimental data demonstrate that front-junction TOPCon cells can achieve an efficiency improvement of 0.2%. This simple and industry-compatible interface-engineering strategy provides a highly scalable pathway for boosting TOPCon and back-contact TOPCon solar cells' performances.