Investigation of ZnO:Al window layer of Cu₂ZnSnS₄ thin film solar cells prepared by non‐vacuum processing

Abstract

Cu2ZnSnS4 (CZTS) thin film solar cells have been fabricated using sol‐gel sulfurizing method under non‐vacuum processing. The solar cells structure is Al/ZnO:Al/CdS/ CZTS/Mo/Soda Lime Glass(SLG) substrate. In our previous reports, the surface of CZTS got rougher as the particle diameter increased. In addition, there were many spots where CZTS layer was not coated enough by ZnO:Al window layer. In this report, in order to improve conversion efficiency of the CZTS solar cells, we focus on the ZnO:Al layer and the effect of an increase in the number of ZnO:Al coating repetition and the dependence on drying time and temperature for ZnO:Al were investigated. Optimized conversion efficiency of 3.61% was achieved with 15 coating repetition of ZnO:Al layer coated at 350 °C and dried for 3 min. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Fabrication of an efficient electrodeposited Cu2ZnSnS4-based solar cells with more than 6% conversion efficiency using a sprayed Ga-doped ZnO window layer

“…Moreover, as shown in entries 7 and 8 in Table 1, the champion devices in the present study exhibited conversion efficiency of 6.4%. Since the best h of CZTS-based solar cells based on a non-vacuum processed window layer was 3.6%, 12 the efficiency obtained in this study is the highest value, even though the value is still lower than our best electrodeposited CZTS-based solar cell using a vacuum-sputtered ITO window layer (8.0%). 19 The wavelength dependence of external quantum efficiency (EQE) for the best CZTS solar cell is shown in Fig.…”

“…4 Although current conversion efficiencies of CZTSbased solar cells are slightly lower than those of analogous CZTSSe-based solar cells, development of CZTS-based solar cells is attractive since they do not contain the toxic Se component, i.e., they should contribute to appreciable reductions of manufacturing costs in the production process. Hence, several approaches for preparation of CZTS thin lms, e.g., evaporation, 4,5 sputtering, 6,7 painting, [8][9][10][11][12][13] and electrodeposition, [14][15][16][17][18][19] have been studied. Among them, electrodeposition has been proved to be a promising method because of its cost effectiveness, e.g., low equipment cost, negligible waste of chemicals with utilization efficiencies close to 100%, possible formation of a compact lm required for solar cell application, scalability, and manufacturability of a large-area polycrystalline lm.…”

“…32 Therefore, almost all of the reported CZTS-based solar cells (as well as CZTSSe-based solar cells) have so far been prepared by using sputtered TCO window layers; there is only example of appreciable efficiency of 3.6% using a sol-gel prepared AZO window layer for a CZTSbased solar cell. 12 Recently, one of the authors (KY) has developed a method of successful growth of a high-quality transparent GZO lm by a conventional atmospheric spray pyrolysis at low temperatures (<150 C) using diethylzinc (DEZ) triethylgallium (TEG) diluted with diisopropyl ether. 33,34 Moreover, the GZO lm was shown to be applicable for a TCO layer of the thin lm solar cell based on a CIGS photoabsorber fabricated by the conventional threestage evaporation process: the efficiency of the thus-obtained device was 10.4%.…”

Ab‐Initio Investigation of the Band Alignment Between Cu2ZnSnS4 and Different Buffer Materials (Al2ZnO4, CeO2, ZnSnO3)

“…Previous attempts to use ZnS, ZnSe, Zn(O,S), and In 2 S 3 as buffer materials have resulted in low power conversion efficiencies (0.8%, 2.2%, 4.6%, and 6.9%, respectively) due to large CBOs (1.1 eV for ZnS, 0.9 eV for Zn(O,S), and 0.4 eV for In 2 S 3 ). On the other hand, first experimental results indicate that ZnO:Al, CeO 2 , and Zn 1− x Sn x O y have potential as buffer materials. For this reason, we use in the present study ab‐initio calculations to investigate the band alignment at the interfaces between p ‐type CZTS and n ‐type Al 2 ZnO 4 , CeO 2 (rutile phase), or ZnSnO 3 , aiming at insights that can support the rational optimization of CZTS solar cells.…”

Fabrication of CZTS Solar Cells Using Electrodeposition Techniques

“…This is typically deposited via sputtering [134,135,131] and is approximately 300 nm thick [134,136,135] (see Figure 1-6). Other, non-vacuum techniques have been trialled, including electrodeposition [137,138] and solution processing [139,140] techniques, although these are not common methods for depositing TCOs on CZTS cells. The TCO used can vary, although indium tin oxide (ITO) and aluminium-doped zinc oxide (AZO) are popular choices [136].…”