Advanced damage-free neutral beam etching technology to texture Si wafer with honeycomb pattern for broadband light trapping in photovoltaics.

Sekhar, Halubai; Fukuda, Tetsuo; Kubota, Tomohiro; Rahman, Mohammad Maksudur; Takato, Hidetaka; Kondo, Michio; Samukawa, Seiji

We introduce a new innovative damage-free neutral beam etching (NBE) technique to transfer a honeycomb resist pattern to silicon (Si) wafer (thickness of 180 µm). Front-surface texturing of Si helps to reduce surface reflection and increase light absorption for solar cell applications. NBE was performed with Cl2 and Cl2/ SF6 gases chemistries, and the influence of the etching time on the etching profiles, surface reflection and potential short-circuit densities (p-JSC) was studied. The Si etching rate with pure Cl2 was ~ 5 nm/min and resulted in anisotropic etch profiles and a minimum surface reflection of 15% at 1000 nm, which is too high for practical use. With the introduction of 5% of SF6, the etching rate increased to 30 nm/min, the etching became isotropic (anisotropy of ~ 1), and sloped sidewalls appeared. NBE with Cl2 (95%)/SF6 (5%) produced a sample with an average surface reflection of 3.7% over the wavelength range 300–1000 nm without any antireflection coating. The minimum surface reflection in this case was ~ 1% at 1030 nm and p-JSC was 40.63 mA/cm2. This type of surface pattern is well suited for low-consumption-material (thin), high-efficiency Si solar cells.

NEUTRAL beams; SILICON solar cells; PHOTOVOLTAIC power generation; ETCHING; HONEYCOMB structures; SOLAR cells; ANTIREFLECTIVE coatings

Journal of Materials Science: Materials in Electronics, 2021, Vol 32, Issue 23, p27449

0957-4522

Academic Journal

10.1007/s10854-021-07121-9