Back-contacted BaSi_2 solar cells: an optical study

Vismara, Robin; Isabella, Olindo; Zeman, Miro

doi:10.1364/oe.25.00a402

Cited by 20 publications

(17 citation statements)

References 30 publications

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“…[25][26][27] Other types of solar cells such as Schottky-type BaSi 2 , BaSi 2 nanowires, BaSi 2 / perovskite stacked layers, and back-contacted BaSi 2 have also been proposed. [28][29][30][31] To further improve the g of BaSi 2 solar cells and to achieve homojunction solar cells, it is important to fabricate high-quality BaSi 2 epitaxial films.…”

Section: Introductionmentioning

confidence: 99%

Impact of Ba to Si deposition rate ratios during molecular beam epitaxy on carrier concentration and spectral response of BaSi2 epitaxial films

Takabe

Deng

Kodama

et al. 2018

Journal of Applied Physics

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Undoped 0.5-lm-thick BaSi 2 epitaxial films were grown on Si(111) substrates with various ratios of the Ba deposition rate to the Si deposition rate (R Ba /R Si) ranging from 1.0 to 5.1, and their electrical and optical properties were characterized. The photoresponse spectra drastically changed as a function of R Ba /R Si , and the quantum efficiency reached a maximum at R Ba /R Si ¼ 2.2. Hall measurements and capacitance versus voltage measurements revealed that the electron concentration drastically decreased as R Ba /R Si approached 2.2, and the BaSi 2 films with R Ba /R Si ¼ 2.0, 2.2, and 2.6 exhibited p-type conductivity. The lowest hole concentration of approximately 1 Â 10 15 cm À3 was obtained for the BaSi 2 grown with R Ba /R Si ¼ 2.2, which is the lowest value ever reported. First-principles calculations suggest that Si vacancies give rise to localized states within the bandgap of BaSi 2 and therefore degrade the minority-carrier properties.

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Section: Introductionmentioning

confidence: 99%

Impact of Ba to Si deposition rate ratios during molecular beam epitaxy on carrier concentration and spectral response of BaSi2 epitaxial films

Takabe

Deng

Kodama

et al. 2018

Journal of Applied Physics

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“…A better understanding of those interfacial activities is a key goal that helps in developing quality-optimization strategies 31 , 36 and designing solar cell architectures. 37 , 38 …”

Section: Introductionmentioning

confidence: 99%

Oxidation-Induced Structure Transformation: Thin-Film Synthesis and Interface Investigations of Barium Disilicide toward Potential Photovoltaic Applications

Tian

Vismara

Doorene

et al. 2018

ACS Appl. Energy Mater.

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Barium disilicide (BaSi2) has been regarded as a promising absorber material for high-efficiency thin-film solar cells. However, it has confronted issues related to material synthesis and quality control. Here, we fabricate BaSi2 thin films via an industrially applicable sputtering process and uncovered the mechanism of structure transformation. Polycrystalline BaSi2 thin films are obtained through the sputtering process followed by a postannealing treatment. The crystalline quality and phase composition of sputtered BaSi2 are characterized by Raman spectroscopy and X-ray diffraction (XRD). A higher annealing temperature can promote crystallization of BaSi2, but also causes an intensive surface oxidation and BaSi2/SiO2 interfacial diffusion. As a consequence, an inhomogeneous and layered structure of BaSi2 is revealed by Auger electron spectroscopy (AES) and transmission electron microscopy (TEM). The thick oxide layer in such an inhomogeneous structure hinders further both optical and electrical characterizations of sputtered BaSi2. The structural transformation process of sputtered BaSi2 films then is studied by the Raman depth-profiling method, and all of the above observations come to an oxidation-induced structure transformation mechanism. It interprets interfacial phenomena including surface oxidation and BaSi2/SiO2 interdiffusion, which lead to the inhomogeneous and layered structure of sputtered BaSi2. The mechanism can also be extended to epitaxial and evaporated BaSi2 films. In addition, a glimpse toward future developments in both material and device levels is presented. Such fundamental knowledge on structural transformations and complex interfacial activities is significant for further quality control and interface engineering on BaSi2 films toward high-efficiency solar cells.

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“…Owing to the large L and α values, a value of η greater than 25% can be expected from a 2-μm-thick BaSi2 p-n junction diode [36]. Other types of solar cells such as BaSi2 nanowires and BaSi2/perovskite stacked layers have also been proposed [37][38][39].…”

Section: Introductionmentioning

confidence: 99%

Effect of BaSi₂template growth duration on the generation of defects and performance of p-BaSi₂/n-Si heterojunction solar cells

Yachi

Takabe

Deng

et al. 2018

Jpn. J. Appl. Phys.

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We investigated the effect of BaSi2 template growth duration (tRDE = 020 min) on the defect generation and performance of p-BaSi2/n-Si heterojunction solar cells. The p-BaSi2 layer grown by molecular beam epitaxy (MBE) was 15 nm thick with a hole concentration of 2 × 10 18 cm −3. The conversion efficiency η increased for films grown at long tRDE, owing to improvements of the open-circuit voltage (VOC) and fill factor (FF), reaching a maximum of η = 8.9% at tRDE = 7.5 min. However, η decreased at longer and shorter tRDE owing to lower VOC and FF. Using deep-level transient spectroscopy, we detected a hole trap level 190 meV above the valence band maximum for the sample grown without the template (tRDE = 0 min). An electron trap level 106 meV below the conduction band minimum was detected for a sample grown with tRDE = 20 min. The trap densities for both films were (12) × 10 13 cm −3. The former originated from the diffusion of Ba into the n-Si region; the latter originated from defects in the template layer. 2 The crystalline qualities of the template and MBE-grown layers were discussed. The root-meansquare surface roughness of the template reached a minimum of 0.51 nm at tRDE = 7.5 min. The a-axis orientation of p-BaSi2 thin films degraded as tRDE exceeded 10 min. In terms of p-BaSi2 crystalline quality and solar cell performance, the optimum tRDE was determined to be 7.5 min, corresponding to approximately 4 nm in thickness.

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Back-contacted BaSi_2 solar cells: an optical study

Cited by 20 publications

References 30 publications

Impact of Ba to Si deposition rate ratios during molecular beam epitaxy on carrier concentration and spectral response of BaSi2 epitaxial films

Impact of Ba to Si deposition rate ratios during molecular beam epitaxy on carrier concentration and spectral response of BaSi2 epitaxial films

Oxidation-Induced Structure Transformation: Thin-Film Synthesis and Interface Investigations of Barium Disilicide toward Potential Photovoltaic Applications

Effect of BaSi₂template growth duration on the generation of defects and performance of p-BaSi₂/n-Si heterojunction solar cells

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Back-contacted BaSi_2 solar cells: an optical study

Cited by 20 publications

References 30 publications

Impact of Ba to Si deposition rate ratios during molecular beam epitaxy on carrier concentration and spectral response of BaSi2 epitaxial films

Impact of Ba to Si deposition rate ratios during molecular beam epitaxy on carrier concentration and spectral response of BaSi2 epitaxial films

Oxidation-Induced Structure Transformation: Thin-Film Synthesis and Interface Investigations of Barium Disilicide toward Potential Photovoltaic Applications

Effect of BaSi2template growth duration on the generation of defects and performance of p-BaSi2/n-Si heterojunction solar cells

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Effect of BaSi₂template growth duration on the generation of defects and performance of p-BaSi₂/n-Si heterojunction solar cells