Optical modeling and characterization of bifacial SiN<sub>x</sub>/AlO<sub>x</sub> dielectric layers for surface passivation and antireflection in PERC
Sofia Tahir, Rabia Saeed, Arslan Ashfaq, Adnan Ali, Khalid Mehmood, Nouf Almousa, Elsammani Ali Shokralla, Romulo R. Macadangdang, Anastasia Soeriyadi, Ruy S. Bonilla
Abstract
Abstract In this research, we analyzed the impact that the optical characteristics of dielectric surface passivation and antireflection coating schemes have on the performance of passivated emitter and rear cell (PERC) silicon solar cells. We employed wafer ray tracer (WRT) and automate for simulation of heterostructure (AFORS‐HET) simulations, as well as experimental characterization of fabricated thin film coatings. We investigated three distinct front surface morphologies: planar surface, upright pyramids, and inverted pyramids. Using WRT, we calculated the photogeneration current densities (J G ) for PERC devices with three schemes: (i) SiN x /AlO x as antireflection coating and passivation stacks on both the front and rear sides, (ii) SiN x antireflection coating on the front side and AlO x passivation layer on the rear side, and (iii) SiN x /AlO x as antireflection coating and passivation stacks on the front side with an AlO x passivation layer on the rear side. Following simulation with optimal J G , two schemes are experimentally evaluated: PECVD SiN x (70 nm) and atomic layer deposition (ALD) AlO x (15 and 25 nm). We confirmed the growth effects and optical properties using X‐ray diffraction, Raman spectroscopy, effective lifetime, and refractive index measurements. The most favorable electrical properties were obtained with SiN x (70 nm, front) and AlO x (25 nm, front and rear), where the AlO x can be deposited via ALD bifacially on a single step, minimizing processing while maintaining passivation performance. Finally, we used AFORS‐HET to simulate the maximum performance of PERC bearing such films. The results showed a V oc = 0.688 V, J sc = 41.42 mA/cm 2 , FF = 84%, and packing conversion efficiency (PCE) = 24.12% as the optimal solar cell performance values.