The 63rd JSAP Spring Meeting, 2016

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Poster presentation

12 Organic Molecules and Bioelectronics » 12.5 Organic solar cells

[19a-P5-1~38] 12.5 Organic solar cells

Sat. Mar 19, 2016 9:30 AM - 11:30 AM P5 (Gymnasium)

9:30 AM - 11:30 AM

[19a-P5-7] Synthesis of the Seven-Membered Ring Fullerene Derivative for Organic Photovoltaics

〇Takafumi Nakagwa1, Keisuke Ogumi2, Ying Zhang1, Hiroshi Okada1, Yutaka Matsuo1 (1.Tokyo Univ., 2.TIRI)

Keywords:Fullerene derivatives,open circuit voltage

We revealed that a new efficient synthetic way for 7-membered cyclic 1,2-diorgano[60]fullerene derivatives (SiOF-7) through a fullerene cation generated by oxidation of fullerene radical. The cyclization reaction of the fullerene dimer proceeded smoothly by using I2 as both the oxidant and the demethylation reagent, affording the SiOF-7 in excellent yield. We demonstrated the performance of organic solar cells containing 7-membered cyclic 1,2-diorgano[60]fullerene derivatives as electron acceptors and employed solution-processed organic solar cells using P3HT as a electron donor. The device configuration was a bulk heterojunction as follows: ITO/PEDOT:PSS/P3HT:SiOF-7/Ca (20 nm)/Al (80 nm). The mixture ratio in the active layer was optimized in the range of 5:3 to 1:1.5. The P3HT:SIOF-7 ratio was optimized to be 5:4 and performance was obtained 1.31% power conversion efficiency (PCE) under 1 sun simulated AM1.5G solar illumination with the higher open circuit voltage (Voc) = 0.71 than PCBM (Voc = 0.61). SiOF-7 had higher lying LUMO level than PCBM and generated 0.1 V higher Voc. Controlling morphology has a significant effect to obtain high PCE, we tested at 80 °C to 150 °C annealing temperature and in the 80 °C annealing device gave the 1.74% PCE without decreasing Voc. On the other hand, annealing with higher temperature devices showed lower PCEs. The morphology of the variety temperature annealing film was examined by the atomic force microscopy. There is no difference in the morphology of the without annealing and 80 °C devices (Rq = 6.66 nm and 5.35 nm), on the other hand, big grains were observed in the 120 °C annealed device (Rq = 4.18 nm), and 150 °C annealed device (Rq = 39.2 nm). We assumed that SIOF-7 grains were grown in the 80 °C annealed film and FF and Jsc increased, however, overgrown aggregations will inhibit charge separation in the thin film and decrease the PCE.