Corresponding Author

Ismail, Yasser

Document Type

Original Article

Subject Areas

Mathematics, Statistics, Computer Science, Physics and Astronomy


Organic solar cells; Polymer molecular weight; Light harvesting; Device performance parameters


In the present article, we try to illustrate the behavior of the most common organic solar cell under the influence of polymermolecular weight (in the range of 21,100-128,800 g/mol) on light harvesting and device performance parameters. The presentwork demonstrates that, the molecular weight of donor polymer plays an important role in the light harvesting and performanceof a common-bulk heterojunction organic solar cell based on poly(3-hexylthiophene) (P3HT), as a donor polymer, and[6,6]-phenyl-C61-butyric acid methyl ester (PCBM), as an acceptor. Through this study it is found that, the optical absorptionof P3HT:PCBM solar cell active layer is increased by increasing P3HT molecular weight. This may be as a result of increasingactive layer thickness and/or increasing backbone chain length of the polymer. In the same time, the absorption wavelengthrange is narrowed and the absorption peak position is shifted towards lower wavelengths due to the entanglement in polymerchains and reduction in polymer crystallinity at higher P3HT molecular weights. The external quantum efficiency (EQE) of theinvestigated solar cells is increased by increasing P3HT molecular weight until the molecular weight that entangles the P3HTchins and, therefore, restricts the charge carrier transfer and, then, reduces the EQE of the P3HT:PCBM solar cell. The performanceparameters of the P3HT:PCBM solar cell are improved by increasing P3HT molecular weights around 25,300 g/moland, after that, deteriorated at higher P3HT molecular weights up to 128,800 g/mol as a result of polymer chain entanglementand reduction of the P3HT crystallinity. The present study shows that the best P3HT molecular weight is 25,300 g/mol, whichproduces power conversion efficiency around 2.5 %.

Included in

Life Sciences Commons