To improve the thermoelectric properties of Cu2GeSe3 via GeSe compensatory compositing strategy

Inducing High Power Factor in Cu2GeSe3-Based Bulk Materials via (Bi, Zn)-Co-doping

“…The XPS survey spectrum exhibited the coexistence of Cu, Ge, Se, Bi, and Zn peaks in the sample, as seen in Figure a, confirming again the inclusion of Bi and Zn. As seen in Figure b, the clear peaks of Cu 2p exhibited two peaks at 952.5 and 932.7 eV, originating from Cu 2p 1/2 and Cu 2p 3/2 of Cu + , respectively. , The spectrum of the Ge 2p exhibited two peaks at 1220.6 and 1218.8 eV in Figure c, which were indexed to 2p 3/2 of Ge 4+ in the sample . The two peaks at 55.3 and 54.0 eV in the Se 3d spectrum as seen in Figure d were attributed to Se 3d 3/2 , which was related to the Se 2– . , As illustrated in Figure e, we found that the high-resolution Bi 4f spectrum displayed two peaks at 166.2 and 160.8 eV, which were assigned to Bi 4f 5/2 and Bi 4f 7/2 of Bi 3+ , respectively .…”

“…As seen in Figure b, the clear peaks of Cu 2p exhibited two peaks at 952.5 and 932.7 eV, originating from Cu 2p 1/2 and Cu 2p 3/2 of Cu + , respectively. , The spectrum of the Ge 2p exhibited two peaks at 1220.6 and 1218.8 eV in Figure c, which were indexed to 2p 3/2 of Ge 4+ in the sample . The two peaks at 55.3 and 54.0 eV in the Se 3d spectrum as seen in Figure d were attributed to Se 3d 3/2 , which was related to the Se 2– . , As illustrated in Figure e, we found that the high-resolution Bi 4f spectrum displayed two peaks at 166.2 and 160.8 eV, which were assigned to Bi 4f 5/2 and Bi 4f 7/2 of Bi 3+ , respectively . While two distinct peaks situated at 163.4 and 158.2 eV were identified as Bi 4f 5/2 and Bi 4f 7/2 of Bi 3+ , severally, exhibiting the presence of Bi 3+ in the sample.…”

“…25 The two peaks at 55.3 and 54.0 eV in the Se 3d spectrum as seen in Figure 4d were attributed to Se 3d 3/2 , which was related to the Se 2− . 24,26 As illustrated in Figure 4e, we found that the high-resolution Bi 4f spectrum displayed two peaks at 166.2 and 160.8 eV, which were assigned to Bi 4f 5/2 and Bi 4f 7/2 of Bi 3+ , respectively. 27 While two distinct peaks situated at 163.4 and 158.2 eV were identified as Bi 4f 5/2 and Bi 4f 7/2 of Bi 3+ , 27 severally, exhibiting the presence of Bi 3+ in the sample.…”

“…As seen in Figure 4b, the clear peaks of Cu 2p exhibited two peaks at 952.5 and 932.7 eV, originating from Cu 2p 1/2 and Cu 2p 3/2 of Cu + , respectively. 23,24 The spectrum of the Ge 2p exhibited two peaks at 1220.6 and 1218.8 eV in Figure 4c, which were indexed to 2p 3/2 of Ge 4+ in the sample. 25 The two peaks at 55.3 and 54.0 eV in the Se 3d spectrum as seen in Figure 4d were attributed to Se 3d 3/2 , which was related to the Se 2− .…”

“…It is worth noting that the high n of the Cu 2 GeSe 3 substrate was associated with the vacancy of Ge. 24,29 According to σ = neμ, the σ of the Cu 2−x Bi x GeSe 3 sample decreased, which was attributed to a decrease of n. Huang et al reported that the n value was obviously reduced from 6.5 × 10 19 cm −3 for pristine Cu 2 GeSe 3 to 1.97 × 10 19 cm −3 for Cu 2−x GeSe 3 sample at 300 K when x was increased to 0.1, and the decrease of n in the Cu 2−x GeSe 3 sample was originated from the increase of Cu vacancy. 30 Due to the electronegativity of Bi (2.01) larger than Cu (1.85), the doping of Bi on the Cu site in the Cu 2 GeSe 3 substrate inevitably contributed to a larger E g as seen in Figure S3, and the valence of Bi and Cu was different hereby raising the vacancy of Cu resulting in decreased n at room temperature.…”