Abstract

Quantum dot (QD)-based luminescent down-shifting (LDS) layers were deposited on Cu2ZnSn(S,Se)4 (CZTSSe) solar cells via the drop-casting method. The LDS layers can easily widen the narrow absorption wavelength regions of single-junction solar cells and enable improvement of the short-circuit current. The optical properties of LDS layers deposited on glass and containing different QD contents were analyzed based on their transmittance, reflectance, and absorbance. The absorber films to be used in the CZTSSe solar cells were determined by X-ray diffraction measurements and Raman spectroscopy to determine their crystal structures and secondary phases, respectively. The completed CZTSSe solar cells with LDS layers showed increased ultraviolet responses of up to 25% because of wavelength conversion by the QDs. In addition, the impact of the capping layer, which was formed to protect the QDs from oxygen and moisture, on the solar cell performance was analyzed. Thus, a maximal conversion efficiency of 7.3% was achieved with the 1.0 mL QD condition; furthermore, to the best of our knowledge, this is the first time that LDS layers have been experimentally demonstrated for CZTSSe solar cells.

Highlights

  • We demonstrate the effects of quantum dot (QD)-based luminescent down-shifting (LDS) layers on CZTSSe solar cells experimentally and the improved absorption in UV regions by up to 25%

  • We present a pioneering work on deposition of QD-based LDS layers on CZTSSe solar cells and show improved UV responses in these solar cells

  • The characteristics of the absorber films used in CZTSSe solar cells were analyzed, and it was confirmed that the Se content was higher than the S content via EDX, XRD, and Raman analyses

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Summary

Introduction

Solar cells made of Cu2 ZnSn(S,Se) (CZTSSe) or Cu(In,Ga)(S,Se) (CIGS) mainly use CdS as the buffer layer, which has the disadvantage of absorbing ultraviolet (UV) light [1,2,3]. To solve this narrow absorption band problem, researchers are studying luminescent down-shifting (LDS) layers that can widen the absorption bands via simpler methods than multijunction or tandem solar cells [4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19].

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