Zn_1–xGe_xO_y Passivating Interlayers for BaSi₂ Thin-Film Solar Cells

Abstract

BaSi 2 is a promising absorber material for nextgeneration thin-film solar cells (TFSCs). For high-efficiency TFSCs, a suitable interlayer should be found for every light absorber. However, such an interlayer has not been studied for BaSi 2 . In this study, we investigated amorphous Zn 1−x Ge x O y films as interlayers for BaSi 2 . The Zn/Ge atomic ratio in the Zn 1−x Ge x O y film and the optical band gap depend on the substrate temperature during sputtering deposition. A suitable i-Zn 1−x Ge x O y /BaSi 2 heterointerface with spike-type conduction band offset was achieved when Zn 1−x Ge x O y was deposited on BaSi 2 at 50 °C. Furthermore, photoresponsivity measurements revealed that Zn 1−x Ge x O y has an excellent surface passivation effect on BaSi 2 . When the thickness of Zn 1−x Ge x O y was 2 nm, a high photoresponsivity of 0.9 A/W was obtained for a 500 nm thick BaSi 2 layer at a wavelength of 780 nm under an applied bias voltage of 0.5 V between the front and rear electrodes, where the photoresponsivity in the short-wavelength region was significantly improved compared with that of BaSi 2 capped with an amorphous Si layer. X-ray photoelectron spectroscopy revealed that the Zn 1−x Ge x O y films suppressed the oxidation of the BaSi 2 surface, decreasing the carrier recombination rate. This is the first demonstration of passivation interlayers for BaSi 2 with suitable band alignment for carrier transport and surface passivation effects.

Sn1–xGexOy and Zn1–xGexOy by Atomic Layer Deposition─Growth Dynamics, Film Properties, and Compositional Tuning for Charge Selective Transport in (Ag,Cu)(In,Ga)Se2 Solar Cells

“…However, the ALD chemistry used in this study limited the growth rate and uniformity of the films. Thus, to fully use the potential of the high-Ge-content ZGO, a different ALD chemistry would need to be developed at this low deposition temperature or an alternative growth method would need to be used, such as CVD, pulsed laser deposition, or sputtering, which have previously shown promising results for Cu 2 O and BaSi 2 absorbers, respectively. ,, In contrast, the TGO ALD process worked very well and there was no obvious hurdle to further increase the Ge content of the resulting films. While using these films as ESLs in ACIGS solar cells does not give the best performance, they are interesting ESL candidates for perovskite solar cells for several reasons.…”

“…One noticeable difference compared to these earlier studies is that these material property trends occur at higher Ge contents in our study. However, both the aforementioned ALD study 35 and a sputter study on ZGO 42 showed that the growth conditions such as deposition temperature had high influence on the morphology and electron affinity of the resulting ZGO films. The measured XPS E v spectra indicated small differences between the ZGO sample series with the addition of Ge (Figure 5b).…”

Demonstration of B-ion-implanted p-BaSi2/n-Si heterojunction solar cells

“…[15][16][17] These properties meet the requirement of high-η thin-film solar cells. Based on the results of such basic research to date, various types of BaSi 2 solar cells have been proposed [18][19][20][21][22][23][24] and fabricated in the form of BaSi 2 /Si, [25][26][27][28][29] BaSi 2 -pn, 30) and n-ZnO/p-BaSi 2 , 31,32) and SnS/BaSi 2 33) by thin-film growth methods such as molecular beam epitaxy (MBE), vacuum evaporation, and sputtering.…”

Structural design of BaSi2 solar cells with a-SiC electron-selective transport layers

“…BaSi 2 solar cells with wide-E g emitter layers have also been proposed to prevent parasitic light absorption in the defective BaSi 2 topmost layers. 25,26) However, most BaSi 2 research has been done on BaSi 2 films on Si substrates except for a few studies. 27,28) Thereby, it is of great importance to form BaSi 2 solar cells on inexpensive substrates like SiO 2 rather than wafer-based Si substrates to take advantage of its high α.…”