Fabrication of texturing antireflection structures in solar cells by using the defocusing exposure in optical lithography

In this paper, we demonstrate a simple method, combining optical lithography and reactive ion etching processes to fabricate antireflective pyramid structures for solar cell applications. By tuning the defocusing distance and exposure dosage of an optical stepper, the optimized pyramid structure in resist can be obtained. After conventional etching processes, the reflection of silicon substrate can be reduced to less than 2% in the spectra regime from 300 to 800 nm. The arrangement of pyramid structures is designed in hexagonal close-packed structures for different directions of sunray. In contrast with previous works, reflectance of texturing structures is affected by optical lithography processes rather than etching processes in our works. The exposure parameters can be easily fine-tuned in an optical stepper. Therefore, high performance of texturing structures in solar cells with a large area and high reproducibility can be achieved. This method is also suitable for the fabrication of antireflective structures on various kinds of solar cell materials by transferring the pyramid resist to underlying materials.