Simultaneous Enhancement of Solar Cell Efficiency and Photostability via Chemical Tuning of Electron Donating Units in Diketopyrrolopyrrole-Based Push鈥揚ull Type Polymers
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- 作者：Tae In Ryu ; Youngwoon Yoon ; Ji-Hoon Kim ; Do-Hoon Hwang ; Min Jae Ko ; Doh-Kwon Lee ; Jin Young Kim ; Honggon Kim ; Nam-Gyu Park ; BongSoo Kim ; Hae Jung Son
- 刊名：Macromolecules
- 出版年：2014
- 出版时间：September 23, 2014
- 年：2014
- 卷：47
- 期：18
- 页码：6270-6280
- 全文大小：805K
- ISSN：1520-5835
文摘
We synthesized a series of push鈥損ull-type copolymers by copolymerizing an electron-deficient diketopyrrolopyrrole with three electron-donating benzodithiophene (BDT) moieties. PDPPDTT, which incorporated a dithienothiophene (DTT), showed a higher power conversion efficiency (PCE) of 6.11% compared to 3.31% for the BDT-based polymer (PDPPBDT). PDPPDTBDT, which incorporated a dithienobenzodithiophene (DTBDT), also exhibited superior performance, with a PCE of 4.75% although this value was lower than that obtained for PDPPDTT. The presence of the DTT unit in the polymer backbone lowered the energy bandgap of the polymer and induced an optimal morphology in the polymer:PC71BM blend film, resulting in higher charge carrier generation. Furthermore, the effectively delocalized frontier orbitals of PDPPDTT enhanced intermolecular interactions between the polymer chains by favoring effective 蟺鈥撓€ stacking, which facilitated charge carrier transport. By contrast, PDPPDTBDT unexpectedly showed a low-crystallinity thin film despite its backbone planarity, which reduced the performance relative to that of PDPPDTT. Importantly, PDPPDTT exhibited significantly better device stability compared to the other polymers in a light soaking test due to the much higher photochemical stability of PDPPDTT. We demonstrated a systematic approach to simultaneously increasing the photovoltaic performances and device stability, and we explored the basis for the structure鈥損roperty relationship that accompanied such improvements.