Comparative Study of the Device Parameters of Schottky Barrier Solar Cells and Homo-Heterojunction Solar Cells

Abstract

This paper reports how the p – CdTe layers grown on Schottky heterostructure influences the opto-electronic behaviour of homo-heterojunction solar cell devices fabricated from CdTe – based device architecture. Two sets of device architecture namely n – n Schottky barrier solar cells and homo-heterojunction – based solar cells with n – n – p device structure was investigated. Schottky barrier solar cells were fabricated using glass/FTO/n – CdS/n – CdTe/Au device structure and this serves as the baseline for comparison with the homo-heterojunction solar cells having p – CdTe layers. The multijunction-based homo-heterojunction solar cells with the n – n – p device architecture was fabricated using glass/FTO/n – CdS/n – CdTe/p – CdTe/Au. The p – CdTe layers grown on n – CdTe affect the solar cell and diode current – voltage characteristics, hence influencing the device electronic parameters. Non – linear and rectifying responses were observed for homo-heterojunction solar cells and n – n Schottky barrier solar cells respectively, when measured under dark condition. Under illumination condition, the cell parameters of the homo-heterojunction solar cells improved as compared to the Schottky barrier solar cells. Short circuit current density values of 27.0 mAcm^-2 and 38.0 mAcm^-2 were obtained for the Schottky barrier and homo-heterojunction – based solar cells respectively. Overall, higher efficiency values of ~4.91% and 7.39% were obtained for the Schottky barrier and homo-heterojunction – based solar cells respectively. Some of the electronic parameters influenced by the insertion of p – CdTe layers on the Schottky heterostructure are: leakage currents, potential barrier heights, ideality factor, series resistance and shunt resistance; the detailed results of these electronic parameters are presented in this article.