title: Steering the efficiency of carbon nanotube-silicon photovoltaic cells by acid vapor exposure: a real-time spectroscopic tracking.
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.
authors.affiliation: †Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, I-25121 Brescia, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Pintossi
authors.affiliation: †Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, I-25121 Brescia, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Pagliara
authors.affiliation: †Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, I-25121 Brescia, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Drera
authors.affiliation: ‡Dipartimento di Fisica, Università degli Studi di Roma Tor Vergata, I-00133 Rome, Italy.|§Istituto Nazionale di Fisica Nucleare, Università di Roma Tor Vergata (INFN-Roma Tor Vergata), I-00133, Rome, Italy.
authors.forename: F
authors.initials: F
authors.lastname: De Nicola
authors.affiliation: ‡Dipartimento di Fisica, Università degli Studi di Roma Tor Vergata, I-00133 Rome, Italy.|§Istituto Nazionale di Fisica Nucleare, Università di Roma Tor Vergata (INFN-Roma Tor Vergata), I-00133, Rome, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Castrucci
authors.affiliation: ‡Dipartimento di Fisica, Università degli Studi di Roma Tor Vergata, I-00133 Rome, Italy.|§Istituto Nazionale di Fisica Nucleare, Università di Roma Tor Vergata (INFN-Roma Tor Vergata), I-00133, Rome, Italy.
authors.forename: M
authors.initials: M
authors.lastname: De Crescenzi
authors.affiliation: ∥Fondazione Bruno Kessler, I-38100 Trento, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Crivellari
authors.affiliation: ∥Fondazione Bruno Kessler, I-38100 Trento, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Boscardin
authors.affiliation: †Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP) and Dipartimento di Matematica e Fisica, Università Cattolica del Sacro Cuore, I-25121 Brescia, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Sangaletti
keywords: CNT−Si hybrid junctions; J−V characteristics; Raman spectroscopy; carbon nanotubes; photoemission; photovoltaics