High power conversion efficiency (PCE) and long-term stability are important requirements for commercialization of organic solar cells (OSCs). In this study, we demonstrate efficient (PCE = 18.60%) and stable (t 80% lifetime > 4000 h) OSCs by developing a series of dimerized smallmolecule acceptors (DSMAs). We prepared three different DSMAs (DYT, DYV, and DYTVT) by using different linkers (i.e., thiophene, vinylene, and thiophene− vinylene− thiophene), to connect their two Y-based building blocks. We find that the crystalline properties and glass transition temperature (T g ) of DSMAs can be systematically modulated by the linker selection. A DYV-based OSC achieves the highest PCE (18.60%) among the DSMA-based OSCs owing to the appropriate backbone rigidity of DYV, leading to an optimal blend morphology and high electron mobility. Importantly, the DYVbased OSC also demonstrates excellent operational stability under 1-sun illumination, i.e., a t 80% lifetime of 4005 h.

We designed and synthesized a series of n-type conjugated polymers by introducing phenylnaphthalenediimide (PNDI) as a novel n-type building block, and investigated the effect of side-chain engineering in the polymer acceptor on the performance of all-polymer solar cells (all-PSCs).

The design of terpolymers is a compelling strategy to improve the polymer solar cell (PSC) performance. However, the terpolymer composition at which the power conversion efficiency (PCE) of associated PSCs is typically optimized generally falls within a very narrow range, complicating the reproducible fabrication of optimal PSCs. In this study, a series of D–A1–D–A2 type random terpolymers (DTTz-X, where X = 10–60) is designed with structurally similar A1 and A2 accepting units. The sulfur atom of the benzothiadiazole subunit in the A1 (DTBT) unit is replaced by a nitrogen atom in the A2 (DTTz) unit, enabling the introduction of an alkyl solubilizing group while maintaining the overall structural properties of the terpolymer system. Consequently, the DTTz-X P Ds maintain good optoelectronic properties at various A1/A2 ratios, while their processability in nonhalogenated solvents is significantly enhanced. Accordingly, the PSC performance of the terpolymer system shows good composition tolerance; i.e., the terpolymer system affords PSCs with PCEs exceeding 15% (up to 16.4%) over a broad range of DTTz compositions (10–40 mol %). This study establishes a useful design strategy for the development of efficient terpolymer donors for reproducible and eco-friendly fabrication of high-performance PSCs.

Organic solar cells (OSCs) based on conjugated block copolymers (CBCs) have gained considerable attention owing to their simple one-pot solution process. However, their power conversion efficiencies (PCEs) require significant improvement. Furthermore, the majority of efficient CBC-based OSCs are processed using environmentally toxic halogenated solvents. Herein, we develop a new CBC (PBDB-T-b-PY5BDT) and demonstrate efficient and stable OSCs achieved by a halogen-free solution process. We design a (D1-A1)-b-(D1-A2)-type CBC (PBDB-T-b-PY5BDT) that shares the same benzodithiophene (BDT) units in donor and acceptor blocks. This alleviates unfavorable molecular interactions between the blocks at their interfaces. The PBDB-T-b-PY5BDT-based devices exhibit a high PCE (10.55%), and they show good mechanical, thermal, and storage stabilities. Importantly, we discuss the potential of our OSCs by preparing two different control systems: one based on a binary polymer blend (PBDB-T:PY5BDT) and another based on a conjugated random copolymer (CRC, PBDB-T-r-PY5BDT). We demonstrate that the photovoltaic performance, device stability, and mechanical robustness of the CBC-based OSCs exceed those of the binary all-polymer solar cells and CRC-based OSCs.

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Use of poly(3-hexylthiophene) (P3HT) enables low-cost manufacture of organic solar cells (OSCs). However, the power conversion efficiencies (PCEs) of the P3HT-based OSCs should be further enhanced. Herein, we report the development of noncovalently fused nonfullerene acceptors (NFAs) that realize high-performance P3HT-based OSCs (>9%). We synthesize regioisomeric NFAs (C4-In and C4-Out) in which the positions of the methyl substituents of their end groups differ. Interestingly, the molecular orientation of the regioisomers in thin film is found to change from edge-on (C4-Out) to face-on (C4-In) orientation, allowing a model study exploring the impact of the microstructure of NFAs on the performance of P3HT-based OSCs. We find that face-on oriented C4-In facilitates both electron and hole transport in a P3HT-based OSC along the vertical direction. In addition, C4-In shows reduced trap densities and suppressed charge recombination in the P3HT:C4-In OSC due to its lower energetic disorder relative to C4-Out. As a result, the P3HT:C4-In OSC (PCE = 9.35%) outperforms a P3HT:C4-Out OSC (PCE = 8.12%) owing to simultaneous enhancement in open-circuit voltage, short-circuit current density, and fill factor. This study demonstrates the importance of molecular orientation of NFAs for developing high-performance P3HT-based OSCs.