Chemical functionalization of carbon nanotubes (CNTs) can strongly affect the efficiency of solar cells due to change of three factors viz, electronic energy structures, interfacial resistance, and electrical field. Therefore, it is worthwhile to investigate the influence of these three factors on the solar cells based on the functionalization of various active molecules in CNTs. In the present study, we investigate the influence of the three factors in the efficiency of superstrate-type Cu(In,Ga)Se-2 (CIGS) solar cells [i.e. F-doped SnO2/CNTs/CdS/CIGS/Au] by encapsulation of electron withdrawing and donating organic molecules inside CNTs. The CIGS solar cell was characterized using the electronic diagram, electrochemical impendence spectroscopy, reverse field emission currents, and currents-voltages curves. (C) 2013 Elsevier B.V. All rights reserved.