Machine Learning Assisted Analysis, Prediction, and Fabrication of High‐Efficiency CZTSSe Thin Film Solar Cells

Abstract

The Earth‐abundant element‐based Cu2ZnSn(S,Se)4 (CZTSSe) absorber is considered as a promising material for thin‐film solar cells (TFSCs). The current record power conversion efficiency (PCE) of CZTSSe TFSCs is ≈13%, and it's still lower than CdTe and CIGS‐based TFSCs. A further breakthrough in its PCE mainly relies on deep insights into the various device fabrication conditions; accordingly, the experimental–oriented machine learning (ML) approach can be an effective way to discover key governing factors in improving PCE. The present work aims to identify the key governing factors throughout the device fabrication processes and apply them to break the saturated PCE for CZTSSe TFSCs. For realization, over 25,000 data points were broadly collected by fabricating more than 1300 CZTSSe TFSC devices and analyzed them using various ML techniques. Through extensive ML analysis, the i‐ZnO thickness is found to be the first, while Zn/Sn compositional ratio and sulfo‐selenization temperature are other key governing factors under thin or thick i‐ZnO thickness to achieve over 11% PCE. Based on these key governing factors, the applied random forest ML prediction model for PCE showed Adj. R2 = >0.96. Finally, the best‐predicted ML conditions considered for experimental validation showed well‐matched experimental outcomes with different ML models.

Unraveling the Effect of Compositional Ratios on the Kesterite Thin-Film Solar Cells Using Machine Learning Techniques

“…Here, the S/(S+Se) ratio in the CZTSSe absorber layer was fixed to ~1% throughout our device fabrication process as it provides high efficiency, so we performed the targeted study on metal cation composition ratio optimization and its effect. The ML-guided fabrication strategy of high-performance CZTSSe TFSCs involves identifying potential rules and heuristics based on compositional ratios viz Cu/(Zn+Sn), Cu/Sn, Cu/Zn, and Zn/Sn [19]. Thus, the DT and CART algorithms were used to determine the optimal compositional ratios.…”

“…The detailed fabrication workflow of the CZTSSe TFSCs and precursor fabrication process is described in our previous work [19]. The diverse sets of precursor composition ratios were prepared through the deposition of Zn, Sn, and Cu metal precursors sequentially via a DC sputtering system on Mo-coated soda lime glass substrates.…”

“…Machine learning (ML) has found promising applications in photovoltaic (PV) technology, offering opportunities to enhance PCE, reduce costs, and optimize performance [17,18]. ML algorithms can analyze large datasets of solar cells, such as device parameters, materials properties, and diverse device fabrication conditions, and can identify key factors that affect device performance [17,19]. By uncovering complex patterns and relationships, ML can guide the design and selection of materials in each layer of highly efficient solar cells.…”

Facile Approach for Metallic Precursor Engineering for Efficient Kesterite Thin-Film Solar Cells

“…Kesterite compounds based on earth-abundant and environmentally friendly elements, specifically Cu 2 ZnSn­(S,Se) 4 (CZTSSe), have garnered attention due to their noteworthy characteristics. − These compounds exhibit a high optical absorption coefficient exceeding 10 4 cm –1 and offer a readily adjustable band gap ( E g ) ranging from 1.0 to 1.5 eV depending on the ratio of sulfur to selenium (i.e., S/(S + Se)). , As of now, the certified power conversion efficiency (PCE) of CZTSSe is approximately 15.0% . Nevertheless, this PCE falls short compared to its competitors, specifically Cu­(In,Ga)­Se 2 (24.0%) and CdTe (22.7%) .…”

Improving the Device Performance of CZTSSe Thin-Film Solar Cells via Indium Doping

“…The kesterite-based Cu 2 ZnSn­(S,Se) 4 (CZTSSe) compounds emerged as a promising photoabsorber material for thin-film solar cells (TFSCs). The CZTSSe absorbers exhibit favorable optoelectronic properties, are low-cost, and are composed of earth-abundant elements with an eco-friendly nature. , Recently, CZTSSe devices have achieved a record power conversion efficiency (PCE) of ∼14.9% at the laboratory scale, which is still lower than the PCE of 23.35% achieved by its closest rival, Cu­(In,Ga)­(S,Se) 2 (CIGSSe) TFSCs. − This lower PCE of the CZTSSe device can be ascribed to a significant open-circuit voltage ( V oc ) deficit caused by electrostatic potential and band gap fluctuations, poor back interface quality, and improper band alignment at the junction region. , Among them are the electrostatic potential and band gap fluctuations caused by forming defects such as Cu Zn or Zn Cu antisite in CZTSSe absorber layers, adversely affecting device performance. Researchers have explored replacing Zn 2+ with alternative elements to mitigate this issue by minimizing defects and improving the device performance.…”