Spray Pyrolysis of CuIn(S,Se)₂ Thin Films Using Hydrazine-based Solutions

Abstract

A novel approach to fabricate CuIn(S,Se) 2 (CIS) thin films through ultrasonically spraying a hydrazine-based precursor solution onto a heated substrate is reported. The effects of the composition of the precursor solutions and the deposition temperature on the CIS film properties were investigated by comparing thin films fabricated using aqueous metal salt solution, anhydrous hydrazine solution, and hydrazine hydrate solution at various deposition temperatures. Crystallite size and texture coefficient in the preferred (112) orientation in the sprayed films increased when the aqueous solution was replaced by hydrazine-based solutions. Additionally, the hydrazine-based precursor solutions resulted in films with better surface smoothness and compositional uniformity than those fabricated using water-based solutions and the hydrazine hydrate solution resulting in the smoothest, most uniform films. The sprayed films were used to fabricate preliminary solar cells that demonstrated a modest photovoltaic response. With optimization, the synthesis of high-quality CIS films by spray pyrolysis from a hydrazine hydrate solution could demonstrate the potential for a low-cost, high-throughput manufacturing process.

Present Status of Solution‐Processing Routes for Cu(In,Ga)(S,Se)2 Solar Cell Absorbers

“…[ 50,62,88 ] Similarly, even anions from metal salt precursors (e.g., NO 3 − ) can oxidize volatile alcohol solvents to create residual carbonaceous impurities in the absorber. [ 89 ] In fact, a major challenge in MI routes entails the adequate removal of residual and nonvolatile impurities such as oxygen (2 wt%, [ 90 ] 5–7 at%, [ 91 ] 15 wt% [ 92 ] ), chlorine (3 wt% [ 90 ] ), carbon (4–7 wt%, [ 55,93 ] 2–3 at% [ 91 ] ), and organic moieties, [ 94 ] from the deposited film.…”

“…[ 135 ] Using metal chloride salt precursor solutions, the authors presented proof‐of‐concept devices with efficiencies of up to 5.6% and 1.2% for substrate and superstrate configurations, respectively. [ 90,135 ] In 2016, Zhang et al. (Raysoll Nanotech) reported the highest PCE of up to 18.1% (certified 17.3%) for a CIGSSe device from hydrazine‐based molecular inks.…”