Laser-enhanced Contact Optimization on iTOPCon Solar Cells

The authors present their work on laser-enhanced contact optimization (LECO) on iTOPCon solar cells. LECO improves the metal-semi-conductor contact resistivity ρc on the boron emitter and the n-TOPCon side from an underfired (thermal budget too low) state of 2.9 and 14.1 mΩcm2 to an enhanced state of 1.8 and 2.9 mΩcm2. Therefore, it enables the reduction of the optimal peak firing temperature, which leads to a decrease of metal induced recombination mainly on the boron emitter side and to minor degree on the n-TOPCon side, as shown in this work. Ultimately, LECO improves iTOPCon solar cells conversion efficiency by 0.6%abs compared with the optimal fired, untreated reference. Submitting those cells to 140°C and 2 suns equivalent irradiation for more than 4 h shows no impact on the conversion efficiency or any sign of light and elevated temperature-induced degradation (LeTID). Confirmed by ISE CalLab, LECO improved iTOPCon solar cells reach 23.8% and 24.1% conversion efficiency on industrial typical wafer formats and processes.