Fabrication and Characteristics of mc-Si Solar Cells with RIE-Textured Surface

Abstract

Reactive ion etching (RIE) texturing is well-known as an effective method to form the surface structure on a multi-crystalline (mc-Si) wafer that has grains with randomly oriented crystallites. The saw damage removal (SDR) process using HF/HNO₃/D.I (HND) solution was employed in this work, since the etching rate of RIE dry etching was lower than that of wet etching. The surface morphology on mc-Si surface was formed by RIE using a gas flow ratio of SF₆:O₂ = 1:1.22. The control of RF power and working pressure could etch the mc-Si surface of the 15.6 × 15.6 cm² area uniformly during RIE texturing process. The surface morphologies textured for 5 and 10 min were needle-like structures and sharp grass-like structures, respectively. Solar cells with the needle-like structure had higher values for open circuit voltage (V_oc), short circuit current (I_sc), fill factor (FF), and efficiency, despite higher reflectance compared to those with the sharp grass-like structure. The cell textured for 10 min was expected to have non-homogeneous emitter layer as the dark I-V curves of the cells textured for 5 and 10 min were compared.

Keywords:

• RIE texturing
• SDR
• reflectance
• needle-like structure
• emitter layer

Acknowledgment

This research was financially supported by the Ministry of Knowledge Economy (MKE), Korean Institute for Advancement of Technology (KIAT) and Dae-Gyeong Leading Industry Office through the Leading Industry Development for Economic Region