A 9% efficiency of flexible Mo-foil-based Cu2ZnSn(S,Se)4 solar cells by improving CdS buffer layer and heterojunction interface

Flexible Cu2ZnSn(S,Se)4(CZTSSe)solar cells show great potential applications due to low-cost,nontoxicity,and stability.The device performances under an especial open circuit voltage(VOC)are limited by the defect recombination of CZTSSe/CdS heterojunction interface.We improve the deposition technique to obtain compact CdS layers without any pinholes for flexible CZTSSe solar cells on Mo foils.The efficiency of the device is improved from 5.7%to 6.86%by highquality junction interface.Furthermore,aiming at the S loss of CdS film,the S source concentration in deposition process is investigated to passivate the defects and improve the CdS film quality.The flexible Mo-foil-based CZTSSe solar cells are obtained to possess a 9.05%efficiency with a VOC of 0.44 V at an optimized S source concentration of 0.68 mol/L.Systematic physical measurements indicate that the S source control can effectively suppress the interface recombination and reduce the VOCdeficit.For the CZTSSe device bending characteristics,the device efficiency is almost constant after1000 bends,manifesting that the CZTSSe device has an excellent mechanical flexibility.The effective improvement strategy of CdS deposition is expected to provide a new perspective for promoting the conversion efficiency of CZTSSe solar cells.

Effect of anneal temperature on electrical and optical properties of SnS:Ag thin films

SnS and Ag films were deposited on glass sub-strates by vacuum thermal evaporation tech-nique successively, and then the films were annealed at different temperatures (0-300℃) in N2 atmosphere for 2h in order to obtain sil-ver-doped SnS ( SnS:Ag ) films. The phases of SnS:Ag films were analyzed by X-ray diffraction (XRD) system, which indicated that the films were polycrystalline SnS with orthogonal struc-ture, and the crystallites in the films were ex-clusively oriented along the(111)direction. With the increase of the annealing temperature, the carrier concentration and mobility of the films first rose and then dropped, whereas their re-sistivity and direct band gap Eg showed the contrary trend. At the annealing temperature of 260℃, the SnS:Ag films had the best properties: the direct bandgap was 1.3 eV, the carrier con-centration was up to 1.132 × 1017 cm-3, and the resistivity was about 3.1 Ωcm.