Applications of Carbon Nanotubes in Different Layers of P3HT: PCBM Bulk Heterojunction Organic Photovoltaic Cells

Abstract

Carbon nanotubes (CNTs) have been synthesized by a simple and efficient pyrolysis technique, and composites of CNTs with PEDOT:PSS, and with P3HT:PCBM blend have been prepared by a modest solution treatment. Bulk heterojunction organic photovoltaic cell (OPVC) has been fabricated by spin coating technique with configuration ITO/PEDOT:PSS/P3HT:PCBM/Al to serve as reference OPVC. Three more OPVCs have been fabricated by the same procedure, the first one with CNTs/PEDOT:PSS composite replacing PEDOT:PSS, second one with CNTs/P3HT:PCBM composite replacing P3HT:PCBM blend, and the third one with both replacements. The performances of all the OPVCs at room temperature have been compared and CNTs have been observed to cause extraordinary increment in the power conversion efficiency (PCE) as well as other electrical parameters of all the devices depending on the layer in which they have been incorporated. To extend the study for understanding further advantages of CNTs incorporation in fighting against degradation, all the fabricated OPVCs have been exposed to open atmosphere and their electrical properties have been measured at room temperature in regular intervals. Encouragingly positive outcomes have been attained, demonstrating not only a well maintained enhancement in the PCE, but also a considerably improved device stability. The best performing OPVC has achieved 24% more PCE and 67% more lifetime in open atmosphere than the reference device, which clearly does indicate the significance of applications of filler CNTs to improve not only the performance but also the stability of OPVCs.