Silicon Nitride (SiN x ) Single and Double‐Layer Coatings for Enhanced Optical, Electrical, and Stability Assessment in n‐TOPCon Solar Cells

Graded silicon‐nitride (SiN x ) single‐layer (SLAR) and double‐layer antireflection coatings (DLAR) are simulated, fabricated, and their reliability assessed for high‐efficiency n‐TOPCon solar cells. Using OPAL 2, the optimal SiN x SLAR (75 nm, R.I = 2.05) and SiN x DLAR (55 nm top layer, R.I = 1.90 and 30 nm bottom layer, R.I = 2.1) configurations were identified and experimentally validated. These parameters were then used in SunSolve simulations, where DLAR achieved a higher power conversion efficiency of 24.21% than SLAR 23.73%, due to enhanced optical impedance matching and improved current density (J sc ) as 40.88 mA/cm 2 for DLAR as compared to 40.51 mA/cm 2 for SLAR. Experimentally, DLAR showed superior transmittance ~95.96%, a wider optical bandgap of 3.75 eV, and an effective carrier lifetime (MCLT) of 729 μs compared to 610 μs for SLAR. FTIR analysis revealed enhanced SiN–H bonding (~5.01 × 10 22 cm −3 ) and reduced Si–H content in DLAR, indicating more stable hydrogen incorporation and improved passivation. Under damp heat stress (85°C/85% RH) SiN x DLAR exhibited lower degradation of 2.46% and recovery of 1.13% in N 2 ambient environment at 250°C than SiN x SLAR 4.28% degradation and 1.72% recovery. Interface trap density ( D it ) and fixed charge ( Q f ) measurements further support the superior chemical and field‐effect passivation of DLAR.