ORCID Profile
0000-0001-9312-5862
Current Organisation
Università Cattolica del Sacro Cuore
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Publisher: Elsevier BV
Date: 12-2015
Publisher: Elsevier BV
Date: 04-2020
DOI: 10.1016/J.JCIS.2020.01.038
Abstract: We observed a 73% enhancement of the power conversion efficiency (PCE) of a photovoltaic cell based on a single wall carbon nanotube/Si hybrid junction after exposing the device to a limited amount (10 ppm) of NO
Publisher: AIP Publishing
Date: 02-2021
DOI: 10.1063/5.0033552
Abstract: The possibility to increase the efficiency of photovoltaic (PV) cells based on hybrid carbon nanotube (CNT)–Si heterojunctions is related to the ability to control the chemical properties of the CNT–Si interface and of the CNT bundle layer. In spite of the encouraging performances of PV cells based on multiwall (MW) CNT, so far few efforts have been made in the study of this device compared to single wall (SW) CNT–Si interfaces. Here, surface and interface effects on the current–voltage characteristic curves of MW CNT–Si hybrid junctions are investigated through exposure to HF vapors and to 10 ppm-NO2 and compared to the effects detected in SW CNT–Si junctions. Quite similar results in terms of open circuit voltage, short circuit current density, and efficiency are found for both cells, suggesting that exposure to HF vapors mostly affects the interface chemical properties, i.e., the silicon oxidation state, that in both junctions reach an optimal state about 50 h after etching. In turn, NO2 exposure has larger effects on the SW-based cell, consistently with the larger surface-to-volume ratio of SW with respect to MW. In both cases, the efficiency value reaches a maximum after 28 min, before dropping when the NO2 molecules desorb from the surface. A combined analysis of current–voltage curves and photoemission data collected along the different phases of gas exposures allowed us to relate changes in the electrical properties to the chemistry of Si at the interface.
Publisher: American Chemical Society (ACS)
Date: 04-05-2015
DOI: 10.1021/AM508973B
Abstract: Hybrid carbon nanotube-silicon (CNT-Si) junctions have been investigated by angle resolved photoemission spectroscopy (AR-XPS) with the aim to clarify the effects of a nonstoichiometric silicon oxide buried interface on the overall cell efficiency. A complex silicon oxide interface has been clearly identified and its origin and role in the heterojunction have been probed by exposing the cells to hydrofluoric (HF) and nitric (HNO3) acid. Real-time monitoring of the cell efficiencies during the steps following acid exposure (up to 1 week after etching) revealed a correlation between the thickness and chemical state of the oxide layer and the cell efficiencies. By matching the AR-XPS and Raman spectroscopy with the electrical response data it has been possible to discriminate the effects on the cell efficiency of the buried SiO(x) interface from those related to CNT acid doping. The overall cell behavior recorded for different thicknesses of the SiO(x) interface indicates that the buried oxide layer is likely acting as a passivating/inversion layer in a metal-insulator-semiconductor junction.
No related grants have been discovered for Luigi Sangaletti.