Effect of diffusion doping-induced defects on shunt resistance affecting Si-nanowire solar cell performance

• Published in: Journal of materials science. Materials in electronics Vol. 35; no. 6; p. 430
• Main Authors: Muduli, Sakti Prasanna, Kale, Paresh
• Format: Journal Article
• Language: English
• Published: New York Springer US 01.02.2024; Springer Nature B.V
• Subjects: Arrays; Characterization and Evaluation of Materials; Chemical etching; Chemistry and Materials Science; Defects; Doping; Electrical measurement; Emission spectra; Emitters; Energy conversion efficiency; Energy gap; Materials Science; Nanowires; Optical and Electronic Materials; Optical reflection; Phosphorus; Phosphorus pentoxide; Photoluminescence; Photovoltaic cells; Shunt resistance; Sol-gel processes; Solar cells
• ISSN: 0957-4522; 1573-482X
• DOI: 10.1007/s10854-024-12190-7

Si nanowires (SiNWs) are preferred over bulk Si for photovoltaics owing to near-zero optical reflection and band gap tunability. However, the cost-effective fabrication of phosphorus-doped SiNWs poses challenges. The work employs metal-assisted chemical etching for SiNW array fabrication and spin-on doping with P 2 O 5 as the phosphorus source to form an n-type emitter. The P 2 O 5 concentration in the phosphosilicate glass (PSG) sol–gel controls the phosphorus-doping level on the SiNWs. Morphological analysis detects a marginal reduction in the SiNW lengths with P 2 O 5 concentration after PSG layer removal. The optical studies show a significant decrease of the average reflectance to 3.99% and a band gap of 1.59 eV for the optimized doping density (fabricated with a P 2 O 5 concentration of 5 mM), leading to a 34.5% improvement in the ultimate efficiency. Raman asymmetric ratio and photoluminescence emission spectra elucidate the possible surface and bulk defects causing the recombination. The resistivity of the optimized phosphorus-doped SiNW array decreases to 3.37 Ω cm due to a significant increase in the donner concentration. The study compares various methods to estimate the internal cell resistances from the illuminated current–voltage measurement and considers the single-diode model accurate. The power conversion efficiency and the fill factor of the optimized solar cell are 4.09% and 43.4%, respectively, limited by the increased series resistance and decreased shunt resistance.