[10a-PB1-1~34] 12.5 Organic solar cells

[10a-PB1-9] Star-shaped Magnesium Tetraethynylporphyrin Bearing Four Peripheral Electron-accepting Diketopyrrolopyrrole Functionalities for Organic Solar Cells

〇Takafumi Nakagwa¹, Huan Wang², Qihui Yue³, Anna Zieleniewska⁴, Hiroshi Okada¹, Keisuke Ogumi⁵, Hiroshi Ueno⁶, Dirk Guldi⁴, Xiaozhang Zhu³, Yutaka Matsuo^1,2 (1.Tokyo Univ., 2.USTC, 3.CAS, 4.FAU, 5.TIRI, 6.NENU)

Keywords:magnesium porphyrin, small molecular organic solar cells, low bandgap

Magnesium tetraethynylporphyrins featuring four electron-deficient diketopyrrolopyrroles (DPP) (Mg-TEP-DPP₄) were synthesized by a Sonogashira coupling andtheir optical and electrochemical properties were investigated. The energy levels were effectively tuned by DPP with or without electron-withdrawing (EWD) end-capping groups. Importantly, all Mg-TEP-DPP₄shave broad absorptions across the visible and NIR absorption regions. Investigations regarding the time-dependent excited state features of Mg-TEP-DPP₄s and kinetics thereof wereperformed by means of the femtosecond transient absorption spectroscopy in combination with multiwavelength and global/target analyses. Importantly, the charge separated state was demonstrated to recombine within 253 ps in benzonitrile. In bulk heterojunction organic solar cells fabricated with Mg-TEP-DPP₄:PC₆₁BM exhibited a PCE of 7.40% upon solvent vapor annealing, which enabled abalanced charge carrier transport, reduced charge recombination, and favorable charge separation/collection.