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Developing low‐cost and high‐performance n‐type polymer semiconductors is essential to accelerate the application of organic thermoelectrics (OTEs). To achieve this objective, it is critical to design strong electron‐deficient building blocks with simple structure and easy synthesis, which are essential for the development of n‐type polymer semiconductors. Herein, we synthesized two cyano‐functionalized highly electron‐deficient building blocks, namely 3,6‐dibromopyrazine‐2‐carbonitrile (CNPz) and 3,6‐Dibromopyrazine‐2,5‐dicarbonitrile (DCNPz), which feature simple structures and facile synthesis. CNPz and DCNPz can be obtained via only one‐step reaction and three‐step reactions from cheap raw materials, respectively. Based on CNPz and DCNPz, two acceptor–acceptor (A–A) polymers, P(DPP‐CNPz) and P(DPP‐DCNPz) are successfully developed, featuring deep‐positioned lowest unoccupied molecular orbital (LUMO) energy levels, which are beneficial to n‐type organic thin‐film transistors (OTFTs) and OTEs performance. An optimal unipolar electron mobility of 0.85 and 1.85 cm2 V−1 s−1 is obtained for P(DPP‐CNPz) and P(DPP‐DCNPz), respectively. When doped with N‐DMBI, P(DPP‐CNPz) and P(DPP‐DCNPz) show high n‐type electrical conductivities/power factors of 25.3 S cm−1/41.4 μW m−1 K−2, and 33.9 S cm−1/30.4 μW m−1 K−2, respectively. Hence, the cyano‐functionalized pyrazine CNPz and DCNPz represent a new class of structurally simple, low‐cost and readily accessible electron‐deficient building block for constructing n‐type polymer semiconductors. [ABSTRACT FROM AUTHOR]

Dopant‐free hole transport layers (HTLs) play a crucial role in achieving high‐efficiency and stable perovskite solar cells (PSCs). However, only a limited number of these HTLs have demonstrated power conversion efficiencies (PCEs) surpassing 21%. Herein, the design and synthesis of two polymeric HTLs with a novel DA'D–A backbone are presented. The incorporation of two A units (benzothiazole and imide functionalized aromatics) in the polymer imparts a rigid backbone, high mobility, appropriate film morphology, excellent thermal stability, and a deeper highest occupied molecular orbital energy level, crucial for achieving a more suitable energy‐level alignment between HTL and perovskite layer. Notably, the champion PSC based on our HTLs exhibits a remarkable PCE of 22.02% with minimal hysteresis and excellent thermal stability, surpassing the performance of devices based on the benchmark polymeric HTL PTAA under identical conditions. These findings underscore the immense potential of our DA'D‐A backbone strategy in developing high‐performance dopant‐free polymer HTLs for enhancing the PCE of PSCs. [ABSTRACT FROM AUTHOR]

The development of high‐performance n‐type polymer semiconductors is powered by the design and synthesis of electron‐deficient building blocks with optimized physicochemical properties. By meticulously installing an imide group onto fluorene and its cyanated derivative, we report here two very electron‐deficient building blocks, imide‐functionalized fluorenone (FOI) and its cyanated derivative (FCNI), both featuring a deep‐lying lowest unoccupied molecular orbital energy level down to −4.05 eV and highly coplanar framework, endowing them ideal units for constructing n‐type polymers. Thus, a series of polymers are built from them, exhibiting unipolar n‐type transport character with a highest electron mobility of 0.11 cm2 V−1 s−1. Hence, FOI and FCNI offer a remarkable platform for accessing high‐performance n‐type polymers and the imide functionalization of appropriate (hetero)arenes is a powerful strategy for developing polymers with deep‐lying LUMOs for n‐type organic electronics. [ABSTRACT FROM AUTHOR]