Investigation on phosphorus doping using H₃PO₄ as doping source by simple dip method and its electrical characterisation

Abstract

In this article, the authors present the work on emitter diffusion in crystalline silicon solar cell fabrication, and determine that phosphorus doping using phosphoric acid (H 3 PO 4 ) with dipping is convenient and cost effective. H 3 PO 4 was mixed with different solvents such as deionised water, ethanol, methanol and butanol. However, deionised water is hydrophobic to the silicon surface. The emitter layers were obtained by varying emulsion concentrations and diffusion temperatures. The sheet resistance of the prepared emitter layers was measured. The sheet resistance varied between 60 and 130 V/% using butanol as a solvent at 900uC for 5 min. Also, butanol as a solvent exhibited uniform sheet resistance over the wafer surface, compared to other solvents. The sheet resistance decreases as the annealing time and temperature was increased. Based on sheet resistance measurements it is evident that this method can be used for solar cell fabrication, and it is cost effective and easy to scale up.

Optimization of Phosphoric Acid-Based Emitter Formation on Silicon Wafer

“…Therefore, in the interest of environmentfriendliness as well as inexpensive manufacturing, use of phosphoric acid (H 3 PO 4 ) as the dopant source represents an almost perfect alternative. Several approaches of phosphorus diffusion have been reported including spin-on (Ahmad et al 2017;Balaji et al 2015;Moon et al 2009), ion implantation (Lee et al 2013;Yang et al 2015), and spray-on phosphoric acid (Basu et al 2016). In most of the reported work, use of commercially-manufactured dopants increases costs and places constraints on its shelf-life.…”

“…These experiments were based on controlled variations in concentrations of H 3 PO 4 four different diffusion temperatures. Moon et al (2009) reported that H 3 PO 4 diluted with deionized (DI) water exhibit non-uniformity over the silicon wafer due to poor surface wettability. This issue was resolved using radio corporation of America (RCA), RCA-2 standard solution to form hydrated surfaces (Ahmad et al 2017).…”

Carbon-Free Solution-Based Doping for Silicon

“…Ref. [ 12 ] presents work using phosphoric acid dissolved in different organic solvents as well as deionized water. However, deionized water resulted in the silicon surface being hydrophobic.…”