Sub-gap defect density characterization of molybdenum oxide
An annealing study for solar cell applications
D. Scire (Università degli Studi di Palermo, TU Delft - Photovoltaic Materials and Devices)
P.A. Prócel (TU Delft - Photovoltaic Materials and Devices)
Antonino Gulino (University of Catania)
O Isabella (TU Delft - Photovoltaic Materials and Devices)
M. Zeman (TU Delft - Electrical Sustainable Energy)
Isodiana Crupi (Università degli Studi di Palermo)
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Abstract
The application of molybdenum oxide in the photovoltaic field is gaining traction as this material can be deployed in doping-free heterojunction solar cells in the role of hole selective contact. For modeling-based optimization of such contact, knowledge of the molybdenum oxide defect density of states (DOS) is crucial. In this paper, we report a method to extract the defect density through nondestructive optical measures, including the contribution given by small polaron optical transitions. The presence of defects related to oxygen-vacancy and of polaron is supported by the results of our opto-electrical characterizations along with the evaluation of previous observations. As part of the study, molybdenum oxide samples have been evaluated after post-deposition thermal treatments. Quantitative results are in agreement with the result of density functional theory showing the presence of a defect band fixed at 1.1 eV below the conduction band edge of the oxide. Moreover, the distribution of defects is affected by post-deposition treatment. [Figure not available: see fulltext.]
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