Morphology and Performance of Poly(2-methoxy-5-(20-ethyl-hexyloxy)-p-phenylenevinylene) (MEH-PPV):(6,6)-phenyl-C61-butyric Acid Methyl Ester (PCBM) Based Polymer Solar Cells

• Published in: Chinese journal of chemistry 2013-06, Vol.31 (6), p.731-736
• Main Authors: Liu, Leijing, Bavel, Svetlana van, Wen, Shanpeng, Yang, Xiaoniu, Loos, Joachim
• Format: Article
• Language: English
• Subjects: Chlorobenzene; Chloroform; Dichlorobenzene; Efficiency; morphology; Photovoltaic cells; Polymers; solar cell; Solar cells; Solar energy; solvent effects; Solvents; thin films; void
• ISSN: 1001-604X; 1614-7065
• DOI: 10.1002/cjoc.201300135

Polymer solar cells were fabricated based on composite films of poly(2‐methoxy‐5‐(2′‐ethyl‐hexyloxy)‐1,4‐phenylenevinylene) (MEH‐PPV):fullerene derivative (6,6)‐phenyl‐C61‐butyric acid methyl ester (PCBM) with weight blend ratio of 1:3, 1:4 and 1:5, spin‐coated from chloroform (CF), chlorobenzene (CB), and o‐dichlorobenzene (ODCB) solutions, respectively. Photoinduced current and power conversion efficiency (PCE) of the devices show a dependence on the solvents. The solar cells have the highest PCE at 1:5 blend ratio. Transmission electron microscopy (TEM) morphology reveals that there are some voids in MEH‐PPV:PCBM films. The void number decreases with the solvent from CF to CB and ODCB. We found the voids are located at the bottom of the films through electron tomography technique by TEM and film bottom‐side morphology study by atomic force microscopy. The charge carrier transport efficiency and collection efficiency should decrease greatly due to the voids, and the more voids the film has, the more degree the efficiencies decrease. PCE of the solar cell prepared from CF is lower than that of the solar cells prepared from CB and ODCB. The void phenomenon of MEH‐PPV:PCBM based solar cell and method to investigate the void position provide an experimental evidence and research mentality to fabricate polymer solar cell with high performance. Some voids were found in the MEH‐PPV:PCBM composite films, and the number of the voids decreases with the solvent. We found the voids are located at the bottom of the films through the electron tomography technique by transmission electron microscopy and film bottom‐side morphology study by atomic force microscopy. The voids are disadvantageous to the device performance.