Empowerment of Photonics in Thin Film Amorphous Silicon Solar Cells
Abstract
In this paper, we investigated the light trapping mechanism of thin-film amorphous silicon (a-Si) solar cells using rigorous coupled wave analysis (RCWA) method. Using optical modeling, the distributed Bragg’s reflector (DBR) is optimized and consists of alternative layers of Si and SiO2 materials. The optical reflectivity of distinct DBR layers was investigated by changing various center wavelengths (400, 600, 800 and 1000 nm). These reflectance spectra showed higher or wider photonic band gap shift due to the parameters of thickness of each layer and incident wavelength. Further, the studied new conformal thin-film solar cell architecture includes nanostructures (indium tin oxide anti-reflection coating, and silver nanogratings) and optimized DBR used as back side reflector. The DBRs and nanogratings helped to fold back the shorter and longer wavelength of light towards the active (a-Si) region and enhanced photon path length and lifetime of photon. Under normal radiation, the collection of the photons was enhanced and also the charge carriers (electron-hole) pair generations were remarkably improved in active regions with less recombination losses. These nanostructures achieved the better light harvesting mechanism and yielded the highest current density of 25.16 mA/cm2. In future, these thin film a-Si solar cells could be fabricated by advanced technology.