Efficient Naphthalenediimide-Based Hole Semiconducting Polymer with Vinylene Linkers between Donor and Acceptor Units

Abstract

We demonstrate a new method to reverse the polarity and charge transport behavior of naphthalenediimide (NDI)-based copolymers by inserting a vinylene linker between the donor and acceptor units. The vinylene linkers minimize the intrinsic steric congestion between the NDI and thiophene moieties to prompt backbone planarity. The polymers with vinylene linkers exhibit electron n-channel transport characteristics under vacuum, similar to the benchmark polymer, P(NDI2OD-T2). To our surprise, when the polymers are measured in air, the dominant carrier type switches from n-to p-type and yield hole mobilities up to 0.45 cm 2 V −1 s −1 with hole to electron mobility ratio of three (μ h /μ e , ∼3), which indicates that the hole density in the active layer can be significantly increased by exposure to air. This increase is consistent with the intrinsic more delocalized nature of the highest occupied molecular orbital of the charged vinylene polymer, as estimated by density functional theory (DFT) calculations, which facilitates hole transport within the polymer chains. This is the first demonstration of an efficient NDI-based hole semiconducting polymer, which will enable new developments in all-polymer solar cells, complementary circuits, and dopable polymers for use in thermoelectrics.

Distannylated Bithiophene Imide: Enabling High‐Performance n‐Type Polymer Semiconductors with an Acceptor–Acceptor Backbone

“…[15a] However,a ll reported BTI-based polymers were synthesized exclusively from dibrominated BTI monomer,which could limit polymer synthetic routes,m olecular weights,a nd structures.I tw as found that Yamamoto,Ullman, and Stille couplings could also be applied for the synthesis of A-A type polymers,h owever the resulting polymers generally showed low number-average molecular weight (M n )a nd (or) structural defects,w hich led to OTFT performance variation over aw ide range. [15a, 21a,b, 22] Marder et al first reported distannylated electron-deficient NDIs, [23] which were then widely used in the development of n-type oligomers and A-A copolymers, [24,25] showing low-lying FMO levels.W hen applied in OTFTs,p olymers PSN-NDI and PBBT-NDI [25b] (Figure 1b)y ielded moderate m e,OTFT values of 0.0011 and 0.039 cm 2 V À1 s À1 ,r espectively, owing to their twisted backbone,a nd the devices based on PBBT-NDI exhibited long-term stability.T oa lleviate steric hindrance associated with NDI, vinylene linker was attached and an ovel NDI monomer containing two (tributylstannyl)vinyl groups was reported by Heeney [26] and Briseno, [27] independently.T he bis(tributylstannyl)vinyl NDI enables development of high-performance unipolar n-type polymers. Polymer P3 featured planar backbone and the OTFTs showed an excellent m e,OTFT up to 3.87 cm 2 V À1 s À1 with ar emarkable stability in air,a nd P4-based devices exhibited af urther increased m e,OTFT of 7.16 cm 2 V À1 s À1 .…”

Distannylated Bithiophene Imide: Enabling High‐Performance n‐Type Polymer Semiconductors with an Acceptor–Acceptor Backbone

“…When applied in OTFTs, polymers PSN‐NDI and PBBT‐NDI (Figure b) yielded moderate μ e,OTFT values of 0.0011 and 0.039 cm 2 V −1 s −1 , respectively, owing to their twisted backbone, and the devices based on PBBT‐NDI exhibited long‐term stability. To alleviate steric hindrance associated with NDI, vinylene linker was attached and a novel NDI monomer containing two (tributylstannyl)vinyl groups was reported by Heeney and Briseno, independently. The bis(tributylstannyl)vinyl NDI enables development of high‐performance unipolar n‐type polymers.…”

Influence of Backbone Chlorination on the Electronic Properties of Diketopyrrolopyrrole (DPP)‐Based Dimers

“…This approach has been proved to be an effective strategy to tune the thin film morphology, which strongly influences the charge separation and charge transport. On the other hand, the material properties can be also tuned via modification the π‐conjugated backbone that has great impact on the electronic structure, such as ionization potential, electron affinity, and electronic delocalization . In recent years, different strategies have been developed to a fine‐tuning energy level through the careful combinations of different subunits or the incorporation of electron‐donating/electron‐withdrawing substituents into backbones .…”

“…On the other hand, the material properties can be also tuned via modification the p-conjugated backbone that has great impact on the electronic structure, such as ionization potential, electron affinity,a nd elec-tronic delocalization. [17][18][19][20][21][22] In recenty ears, different strategies have been developed to af ine-tuning energy level through the careful combinationsofdifferent subunits or the incorporation of electron-donating/electron-withdrawings ubstituents into backbones. [23][24][25][26][27] For example, fluorine atom has been widely incorporated into polymer backbones that significantly influence the energy level, backbonep lanarity,s olubility,a nd crystallization.…”