Efficient Cu₂ZnSnS₄solar cells spray coated from a hydro-alcoholic colloid synthesized by instantaneous reaction

Abstract

A fast simple preparation based on spraying a Cu–Zn–Sn–S colloid and a sequentially annealing in N2and H2S yields compact, continuous layers with grain size of micron order.

Fine‐Tuning the Sn Content in CZTSSe Thin Films to Achieve 10.8% Solar Cell Efficiency from Spray‐Deposited Water–Ethanol‐Based Colloidal Inks

“…As mentioned above, our standard fabrication method uses a two-step annealing process: The fi rst annealing in N 2 leads normally (0% Sn) to compact fi lms with large grains (micrometer size), but at the expense of the formation of secondary phases, as it has been shown by X-ray diffraction (XRD) and energy-dispersive X-ray microanalysis (EDX) mapping in our previous publications. [ 2,5 ] When adding Sn, the secondary phases are still present after the N 2 annealing step, as observed by XRD measurements (not shown here), the peaks of the SnS phase being particularly enhanced. Surprisingly, we observed that upon increasing the Sn content in the ink, the fi lms do not achieve full compactness after the fi rst annealing step in N 2 (see wileyonlinelibrary.com fi lms obtained from the standard ink (0% Sn added).…”

“…[ 5 ] . The experimental details regarding the colloid synthesis, the ink preparation, and the spray deposition technique can be found in ref.…”

“…[ 2,5 ] The second annealing step, performed in the presence of Se and SnS vapors, plays two roles: (i) The incorporation of Se into the fi lm and (ii) a fi lm healing by the recovery of the CZTSSe phase from the secondary phases formed in the fi rst annealing step. As mentioned above, our standard fabrication method uses a two-step annealing process: The fi rst annealing in N 2 leads normally (0% Sn) to compact fi lms with large grains (micrometer size), but at the expense of the formation of secondary phases, as it has been shown by X-ray diffraction (XRD) and energy-dispersive X-ray microanalysis (EDX) mapping in our previous publications.…”

“…2015, 5, 1501404 www.MaterialsViews.com www.advenergymat.de Figure 3. Instead, the overall stoichiometry of the fi lm is partially dominated by the presence of some remaining secondary phases, in particular the Zn(S,Se) phase, which could be easily observed in thin slices of the fi lm by TEM [ 2,5 ] for fi lms made using Znrich precursor's ratios. of the Sn added in each case, we could fi nd a reasonably good agreement: The average difference is about 0.5% points, except for the 4% Sn addition, which somewhat diverges from the main trend.…”

“…[ 3,4 ] Indeed, our approach is based upon the instantaneous synthesis of a Cu-Zn-Sn-S colloid from water and acetonitrile precursor solutions. [ 5 ] This colloid is then formulated into a water (90%)/ethanol (10%) ink which is spray coated on a heated substrate and exposed to two subsequent annealing treatments aiming at growing large grains and incorporating selenium in the active layer. A cell effi ciency of 8.6% has been recently obtained with this simple fabrication method ( J SC = 30.9 mA cm −2 , V OC = 0.46 V, FF = 0.60).…”