INFLUENCE OF POLYMER MOLECULAR WEIGHT ON LIGHT HARVESTING AND PERFORMANCE PARAMETERS OF THE ORGANIC SOLAR CELL | ||||
| Al-Azhar Bulletin of Science | ||||
| Article 1, Volume 25, Issue 2-B, December 2014, Page 1-8 PDF (505.86 K) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/absb.2014.22603 | ||||
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| Authors | ||||
| Yasser A. M. Ismail* 1; Naoki Kishi2; Tetsuo Soga2 | ||||
| 1Departments of *Third Generation Solar Cells Laboratory, Physics, Faculty of Science, Al-Azhar University, Assiut 71121, Egypt | ||||
| 2Frontier Materials, Nagoya Institute of Technology, Nagoya 466-8555, Japan | ||||
| Abstract | ||||
| In the present article, we try to illustrate the behavior of the most common organic solar cell under the influence of polymer molecular weight (in the range of 21,100-128,800 g/mol) on light harvesting and device performance parameters. The present work demonstrates that, the molecular weight of donor polymer plays an important role in the light harvesting and performance of 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 absorption of P3HT:PCBM solar cell active layer is increased by increasing P3HT molecular weight. This may be as a result of increasing active layer thickness and/or increasing backbone chain length of the polymer. In the same time, the absorption wavelength range is narrowed and the absorption peak position is shifted towards lower wavelengths due to the entanglement in polymer chains and reduction in polymer crystallinity at higher P3HT molecular weights. The external quantum efficiency (EQE) of the investigated solar cells is increased by increasing P3HT molecular weight until the molecular weight that entangles the P3HT chins and, therefore, restricts the charge carrier transfer and, then, reduces the EQE of the P3HT:PCBM solar cell. The performance parameters of the P3HT:PCBM solar cell are improved by increasing P3HT molecular weights around 25,300 g/mol and, after that, deteriorated at higher P3HT molecular weights up to 128,800 g/mol as a result of polymer chain entanglement and reduction of the P3HT crystallinity. The present study shows that the best P3HT molecular weight is 25,300 g/mol, which produces power conversion efficiency around 2.5 %. | ||||
| Keywords | ||||
| Organic solar cells; Polymer molecular weight; Light harvesting; Device performance parameters | ||||
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