Modified Back Contact Interface of CZTSe Thin Film Solar Cells: Elimination of Double Layer Distribution in Absorber Layer

Abstract

Double layer distribution exists in Cu2SnZnSe4 (CZTSe) thin films prepared by selenizing the metallic precursors, which will degrade the back contact of Mo substrate to absorber layer and thus suppressing the performance of solar cell. In this work, the double‐layer distribution of CZTSe film is eliminated entirely and the formation of MoSe2 interfacial layer is inhibited successfully. CZTSe film is prepared by selenizing the precursor deposited by electrodeposition method under Se and SnSex mixed atmosphere. It is found that the insufficient reaction between ZnSe and Cu‐Sn‐Se phases in the bottom of the film is the reason why the double layer distribution of CZTSe film is formed. By increasing Sn content in the metallic precursor, thus making up the loss of Sn because of the decomposition of CZTSe and facilitate the diffusion of liquid Cu2Se, the double layer distribution is eliminated entirely. The crystallization of the formed thin film is dense and the grains go through the entire film without voids. And there is no obvious MoSe2 layer formed between CZTSe and Mo. As a consequence, the series resistance of the solar cell reduces significantly to 0.14 Ω cm2 and a CZTSe solar cell with efficiency of 7.2% is fabricated.

Band-gap-graded Cu2ZnSn(S,Se)4 drives highly efficient solar cells

“…The lattice expansion is mainly caused by Cd doping, due to the larger ionic radius of Cd 2+ (0.92 Å) than of Zn 2+ (0.74 Å) or Cu + (0.74 Å). [43][44][45] In addition, extensive stacking faults and dislocations are present in the IFFT pattern of CdS for the RT device, while these are not observed on the corresponding HT device. This indicates that the new phase Cu 2 S formed after annealing eliminates the dislocations of the RT device, which is more favorable for reducing the carrier recombination.…”

Green Atmospheric Aqueous Solution Deposition for High Performance Cu2ZnSn(S,Se)4 Thin Film Solar Cells

“…Kesterite Cu 2 ZnSn(S,Se) 4 (CZTSSe) as a kind of promising candidate for photovoltaic material is booming for scalable photovoltaic applications due to its low‐cost, earth‐abundant elemental constituents, and suitable bandgap . However, kesterite‐based solar cells with a 12.6% record efficiency is still much younger and far lower than the well‐developed chalcopyrite photovoltaics based on Cu(In,Ga)Se 2 (CIGS) having already demonstrated a power conversion efficiency (PCE) of over 20% .…”

CZTS thin film solar cells on flexible Molybdenum foil by electrodeposition-annealing route

“…On the other hand, a thick MoS 2 layer at the CZTS/Mo interface can influence the total series resistance of the device [41]. However, Zhang et al recently demonstrated 7.2% efficient CZTS solar cells without having any MoS 2 layer [57]. By the way, HR-TEM suggest around 50 nm of MoS 2 has been formed in our solar cells (Fig.…”