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.