Subtle Polymer Donor and Molecular Acceptor Design Enable Efficient Polymer Solar Cells with a Very Small Energy Loss

Xiaopeng Xu, Kui Feng, Young Woong Lee, Han Young Woo, Guangjun Zhang, Qiang Peng

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

A new wide bandgap polymer donor, PNDT-ST, based on naphtho[2,3-b:6,7-b′]dithiophene (NDT) and 1,3-bis(thiophen-2-yl)-5,7-bis(2- ethylhexyl)benzo[1,2-c:4,5-c′]dithiophene-4,8-dione (BDD) is developed for efficient nonfullerene polymer solar cells. To better match the energy levels, a new near infrared small molecule of Y6-T is also developed. The extended π-conjugation and less twist of PNDT-ST provides it with higher crystallinity and stronger aggregation than the PBDT-ST counterpart. The higher lowest occupied molecular orbital level of Y6-T than Y6 favors the better energy level match with these polymers, resulting in improved open circuit voltage (Voc) and power conversion efficiency (PCE). The high crystallinity and strong aggregation of PNDT-ST also induces large phase separation with poorer morphology, leading to lower fill factor and reduced PCE than PBDT-ST. To mediate the crystallinity and optimize the morphology, PNDT-ST and PBDT-ST are blended together with Y6-T, forming the ternary blend devices. As expected, the two compatible polymers allow continual optimization of the morphology by varying the blend ratio. The optimized ternary blend devices deliver a champion PCE as high as 16.57% with a very small energy loss (Eloss) of 0.521 eV. Such small Eloss is the best record for polymer solar cells with PCEs over 16% to date.

Original languageEnglish
Article number1907570
JournalAdvanced Functional Materials
DOIs
Publication statusAccepted/In press - 2020 Jan 1

Keywords

  • energy loss
  • nonfullerene acceptors
  • polymer solar cells
  • ternary blends
  • wide bandgap polymer donors

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

Fingerprint Dive into the research topics of 'Subtle Polymer Donor and Molecular Acceptor Design Enable Efficient Polymer Solar Cells with a Very Small Energy Loss'. Together they form a unique fingerprint.

Cite this