Synergistically Improved Molecular Doping and Carrier Mobility by Copolymerization of Donor–Acceptor and Donor–Donor Building Blocks for Thermoelectric Application

Abstract

In this work, it is demonstrated that random copolymerization is a simple but effective strategy to obtain new conductive copolymers as high‐performance thermoelectric materials. By using a polymerizing acceptor unit diketopyrropyrrole with donor units thienothiophene and oligo ethylene glycol substituted bithiophene (g32T), it is found that strong interchain donor–acceptor interactions ensure good film crystallinity for charge transport, while donor–donor type building blocks contribute to effective charge transfers. Hall effect measurements show that the high electrical conductivity results from increased free carriers with simultaneously improved mobility reaching over 1 cm2 V−1 s−1. The synergistic effect of improved molecular doping and carrier mobility, as well as a high Seebeck coefficient ascribed to the structural disorder along polymer chains via random copolymerization, results in an impressive power factor up to 110 µW K−2 m−1 which is 10 times higher than that of solution‐processed polythiophenes.

Achieving Efficient p‐Type Organic Thermoelectrics by Modulation of Acceptor Unit in Photovoltaic π‐Conjugated Copolymers

“…Meanwhile, the strong electron‐withdrawing capability of A moiety could strengthen the energetic disorder along the polymer chains and tuning the shape of density‐of‐states (DOS), thus enlarging the value of E F − E T , which is proportional to S . [ 27 ] Accordingly, the peak room‐temperature PFs of PBDP‐T, PTB7‐Th, and PBDB‐T are acquired to be as high as 20.1, 46.0, and 105.5 µW m −1 K −2 at [FeCl 3 ] = 10, 5, and 10 m m , respectively, as shown in Figure 4c . When comparing with the literature results of D– π , [ 14 , 15 , 16 , 17 , 18 , 19 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ] A– π , [ 20 , 49 , 50 , 51 ] and D–A [ 23 , 24 , 25 , 26 , 27 , 52 , 53 , 54 ] type copolymers as summarized in Figure 4d , it has been rarely reported with S values over 100 µV K −1 , most of which were obtained by those D–A copolymers.…”

“…[ 27 ] Accordingly, the peak room‐temperature PFs of PBDP‐T, PTB7‐Th, and PBDB‐T are acquired to be as high as 20.1, 46.0, and 105.5 µW m −1 K −2 at [FeCl 3 ] = 10, 5, and 10 m m , respectively, as shown in Figure 4c . When comparing with the literature results of D– π , [ 14 , 15 , 16 , 17 , 18 , 19 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ] A– π , [ 20 , 49 , 50 , 51 ] and D–A [ 23 , 24 , 25 , 26 , 27 , 52 , 53 , 54 ] type copolymers as summarized in Figure 4d , it has been rarely reported with S values over 100 µV K −1 , most of which were obtained by those D–A copolymers. This work achieves an impressively high PF over 100 µW m −1 K −2 while preserving a superior S beyond 200 µV K −1 as shown in Table S6 , Supporting Information, holding great promise in wearable skin electronics, taken as one example.…”

“…The resulting optimal copolymer PDPP‐g 3 2T 0.3 with finely tuned D/A unit ratios delivered an excellent PF as high as 110 µW m −1 K −2 with a moderate S of 56 µV K −1 . [ 27 ] In general, owing to the sufficient energetic disorder in their molecular structures, D−A copolymers exhibit a relatively higher S than D− π analogues. [ 28 ] Nonetheless, a multitude of studies have been devoted to increasing the doping efficiency and hence σ , yet the methods of obtaining high S are rarely explored.…”

Influence of Backbone Curvature on the Organic Electrochemical Transistor Performance of Glycolated Donor–Acceptor Conjugated Polymers

“…As with many reported glycolated conjugated polymers, the analysis of molecular weight was complicated by the tendency of both polymers to aggregate in solution. [ 36 , 37 ] Examining different concentrations of PgBT(F)2gT by GPC revealed an estimated M n =10 kDa and Đ =1.7 against polystyrene standards, whereas the main peak of PgBT(F)2gTT exhibited unrealistically high values irrespective of concentration with a small peak also apparent at M n =3.8 kDa and Đ =1.2 (Figures S11–S13). The structures of both polymers were confirmed by 1 H and 19 F NMR, as well as MALDI‐ToF analysis (Figures S23–S28).…”

3,4,5‐Trimethoxy Substitution on an N‐DMBI Dopant with New N‐Type Polymers: Polymer‐Dopant Matching for Improved Conductivity‐Seebeck Coefficient Relationship

“…[1] Doping is a common and effective way to increase the conductance of organic electronic devices, for example OTFTs [2] and organic thermoelectric devices (OTEs). [3] Thanks to the appealing advantages of mechanical flexibility and nontoxicity, [4] organic thermoelectrics, especially polymer thermoelectrics, are under consideration for wearable devices. Both p-type [5] and n-type [6] organic thermoelectrics usually show inherently low thermal conductivity (k: 0.2-0.5 Wm À1 K À1 ), beneficial for a high Figure of merit ZT.…”