Improvements in electrical properties for the Sn-rich Cu2−xZnSnSe4 bulks with mobility above 50 cm2/V s

•Sn-rich CZTSe bulks with various Cu contents were prepared by reactive sintering.•The rich in Sn for CZTSe is not favorable as forming n-type and low mobility.•Our Sn-rich Cu2−xZn0.9Sn1.1Se4 shows p-type at x = 0–0.1 and n-type at x = 0.2–0.3.•p-type Sn-rich CZTSe has np < 1019 cm−1 and high μ > 50 cm2/V s.•Properties are related to four kinds of defects of VCu1-, CuB, SnZn2+, and ZnCu1+.

Effects of the Cu variation in Cu2−xZn0.9Sn1.1Se4 (Sn-rich CZTSe) bulks with x = 0–0.3 on the morphological, structural, and electrical properties have been investigated. Conventionally, the rich in Sn is prohibited for CZTSe because of the formation of the n-type and low electrical mobility. Cu2−x(Zn0.9Sn1.1)Se4 pellets show as the p-type at x = 0 and 0.1 and the n-type at x = 0.2 and 0.3. Sn-rich CZTSe at x = 0 and 0.1 has high mobilities of 87.1 and 58.4 cm2/V s and favorable hole concentrations of 7.52 × 1017 and 4.88 × 1017 cm−3, respectively. SEM surface images have shown that the grains are less densely packed as the copper content decreases. The non-stoichiometric composition of Sn-rich CZTSe under various Cu contents can lead to the intrinsic defects, with which the changes in the structural and electrical properties of the bulks with the Cu ratio can be explained. This work provides the promising results for Sn-rich CZTSe with the Sn excess to control the hole concentration and the Cu content to keep high electrical mobility.

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