Open AccessAchieving Efficient p‐Type Organic Thermoelectrics by Modulation of Acceptor Unit in Photovoltaic π ‐Conjugated Copolymers
Author(s) -
Tang Junhui,
Ji Jingjing,
Chen Ruisi,
Yan Yongkun,
Zhao Yan,
Liang Ziqi
Publication year - 2022
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.202103646
Subject(s) - conjugated system , photovoltaic system , materials science , copolymer , unit (ring theory) , acceptor , thermoelectric materials , modulation (music) , optoelectronics , polymer , electrical engineering , physics , engineering , thermal conductivity , composite material , condensed matter physics , mathematics education , mathematics , acoustics
π ‐Conjugated donor (D)−acceptor (A) copolymers have been extensively studied as organic photovoltaic (OPV) donors yet remain largely unexplored in organic thermoelectrics (OTEs) despite their outstanding mechanical bendability, solution processability and flexible molecular design. Importantly, they feature high Seebeck coefficient ( S ) that are desirable in room‐temperature wearable application scenarios under small temperature gradients. In this work, the authors have systematically investigated a series of D−A semiconducting copolymers possessing various electron‐deficient A‐units (e.g., BDD, TT, DPP) towards efficient OTEs. Upon p‐type ferric chloride (FeCl 3 ) doping, the relationship between the thermoelectric characteristics and the electron‐withdrawing ability of A‐unit is largely elucidated. It is revealed that a strong D−A nature tends to induce an energetic disorder along the π ‐backbone, leading to an enlarged separation of the transport and Fermi levels, and consequently an increase of S . Meanwhile, the highly electron‐deficient A‐unit would impair electron transfer from D‐unit to p‐type dopants, thus decreasing the doping efficiency and electrical conductivity (σ). Ultimately, the peak power factor (PF) at room‐temperature is obtained as high as 105.5 µW m −1 K −2 with an outstanding S of 247 µV K −1 in a paradigm OPV donor PBDB‐T, which holds great potential in wearable electronics driven by a small temperature gradient.