Cell Fabrication and Characterization.
Based on the n-type silicon substrates, the proof-of-concept 2 × 2 cm2 solar cells were fabricated. A p-type emitter was thermally diffused by a BBr3 source through a furnace after texturing in KOH solution and the Radio Corporation of America (RCA) standard cleaning procedure. After that, Al2O3/SiNx layers for passivation and antireflection were applied to the front side of the emitter deposited by atomic layer deposition (ALD) and plasma-enhanced chemical vapor deposition (PECVD), respectively. The back surface of the solar cell was also passivated by the SiNx layer. An array of 25 μm-diameter contact holes which account for 1% of the backside were opened with a picosecond laser. The front surface Ag metal fingers were formed by the screen-printing paste and annealing process. The solar cells were finished by a thermally evaporated Al (800 nm) or various thicknesses SrF2/Al stack layer on the backside.
The current-voltage (J-V ) measurements were carried out on Solar Cell I-V Tester (VS-6821M) under standard test conditions (25℃, AM 1.5G, 1000W/m2). The illumination intensity was checked by the WPVS reference solar cell. A quantum efficiency-reflection (QE-R) spectral testing instrument from Enli-tech corporation was used to characterize the external quantum efficiency (EQE) and reflectivity.