Development of system to grow ZnO films by plasma assisted reactive evaporation with improved thickness homogeneity for using in solar cells

Abstract

This paper focuses on the development and evaluation of an automated system for the deposition of ZnO thin films with suitable properties to be used in solar cells, using the plasma assisted reactive evaporation (PARE) method. A description is made of both the electronic system developed and the Zn evaporation source implemented with a novel design based on the effusion cell concept. This development made it possible to significantly improve both the low reproducibility of the optoelectric properties and the inhomogeneity of the thickness of the ZnO films that were deposited using a previous version of the PARE system developed.The improvement of thickness homogeneity and the applicability of the ZnO thin films for use in solar cells was verified through measurements of the thickness, spectral transmittance and electrical resistivity of samples deposited on 5 × 4 cm2 glass substrates. By optimizing the preparation parameters, it was possible to deposit thin ZnO films with improved thickness homogeneity, characterized by having resistivities varying between 9.5 × 10−4 Ωcm (n+-ZnO) and 2 × 104 Ωcm (i-ZnO) and transmittances greater than 85% (in the visible region). The structural, optical and morphological properties of the ZnO films were studied by different techniques.