Compositional and Interfacial Modification of Cu₂ZnSn(S,Se)₄ Thin‐Film Solar Cells Prepared by Electrochemical Deposition

Abstract

A highly efficient Cu2 ZnSn(S,Se)4 (CZTSSe)-based thin-film solar cell (9.9%) was prepared using an electrochemical deposition method followed by thermal annealing. The Cu-Zn-Sn alloy films was grown on a Mo-coated glass substrate using a one-pot electrochemical deposition process, and the metallic precursor films was annealed under a mixed atmosphere of S and Se to form CZTSSe thin films with bandgap energies ranging from 1.0 to 1.2 eV. The compositional modification of the S/(S+Se) ratio shows a trade-off effect between the photocurrent and photovoltage, resulting in an optimum bandgap of roughly 1.14 eV. In addition, the increased S content near the p-n junction reduces the dark current and interface recombination, resulting in a further enhancement of the open-circuit voltage. As a result of the compositional and interfacial modification, the best CZTSSe-based thin-film solar cell exhibits a conversion efficiency of 9.9%, which is among the highest efficiencies reported so far for electrochemically deposited CZTSSe-based thin-film solar cells.

Aqueous-Solution-Processed Cu2ZnSn(S,Se)4 Thin-Film Solar Cells via an Improved Successive Ion-Layer-Adsorption–Reaction Sequence

“…17−20 Although a highest efficiency of ∼9.9% has been achieved for an electrodeposited CZTSSe TFSC, there are several issues associated with the electrodeposition of CZTS-based absorber layers. 21 Electrodeposition of stacked elemental layers often results in spatial compositional inhomogeneity in the absorber layer after sulfurization/selenization owing to the nonuniform deposition of Zn on the islandlike growth of Sn onto the Cu surface. 22,23 On the other hand, coelectroplating of the precursors shows a dendritic growth, which generally results in an uneven surface microstructure with spatial distribution of micron-sized grains after sulfurization/selenization.…”

Improved interfacial properties of electrodeposited Cu2ZnSn(S,Se)4 thin‐film solar cells by a facile post‐heat treatment process

“…As a result, the efficiency of the best CZTSSe solar cells was significantly enhanced from 7.11% (reference CZTSSe device) to 9.40%, which is close to the highest reported efficiency of CZTSSe thin-film solar cells prepared by electrodeposition (i.e., 9.9%). 23 The rough CZTSSe thin-film solar cells with effectively reduced interfacial detrimental defects through the PHT process exhibited reduced charge recombination and improved photovoltaic performances like higher V OC and FF. film deposited by electrodeposition is known to be relatively high 5,25 compared with those deposited by other techniques such as sputtering, 26 spray method, 27 and thermal co-evaporation.…”

“…Various methods have been used to prepare CZTSSe-based thinfilm solar cells, including sputtering, 2,7,[13][14][15] thermal evaporation, 16 electron-beam evaporation, 17 sol-gel methods, 18,19 spin coating, 20 spray pyrolysis, 21 electrochemical deposition, 5,22,23 and the hydrazine-slurry method. 6 However, these methods have shortcomings such as expensive precursors, time-consuming processes, complicated apparatus, and the use of toxic substances (e.g., hydrazine).…”

“…is an industrially attractive technique for the fabrication of low-cost, uniform, and large-area CZT precursors as the process is technically simple, with low energy and time consumption, high precursor usage, and good compatibility with mass production. 5,8,22,23 The importance of producing CZTSSe thin-film solar cells using the co-electrochemical method continues to grow and relevant research focused on preparing high performance CZTSSe thin-film solar cells is essential.…”

Thickness optimization of the ZnO based TCO layer in a CZTSSe solar cell. Evolution of its performance with thickness when external temperature changes.

“…Watson, in 2013 obtained the best performances for CZTSSe based solar cells with power conversion efficiency equal to 12.6% [8,9]. Several research groups reported the growth and fabrication of CZTSSe solar cells using various methods such as sputtering followed sulfo-selenization [10,11], solution growth process [12,13], nano-particle approach [14,15], electrodeposition [16,17], ink jet printing [18], pulsed laser deposition [19,20], ball milling and hybrid ink followed by sulfoselenization [21,22].…”