Molecular Insights of Non‐fused Ring Acceptors for High‐Performance Non‐fullerene Organic Solar Cells

Precisely Manipulating Molecular Packing via Tuning Alkyl Side-Chain Topology Enabling High-Performance Nonfused-Ring Electron Acceptors

In the development of high-performance organic solar cells (OSCs), the self-organization of organic semiconductors plays a crucial role. This study focuses on the precisely manipulation of molecular assemble via tuning alkyl side-chain topology in a series of low-cost nonfused-ring electron acceptors (NFREAs). Among the three NFREAs investigated, DPA-4, which possesses an asymmetric alkyl side-chain length, exhibits a tight packing in the crystal and high crystallinity in the film, contributing to improved electron mobility and favorable film morphology for DPA-4. As a result, the OSC device based on DPA-4 achieves an excellent power conversion efficiency of 16.67 %, ranking among the highest efficiencies for NFREA-based OSCs.

Low-Cost Fully Non-fused Ring Acceptor Enables Efficient Organic Photovoltaic Modules for Multi-Scene Applications

Organic photovoltaic (OPV) cells, with highly tunable light-response ranges, offer significant potential for use in driving low-power consumption off-grid electronics in multi-scenarios. However, development of photoactive layer materials that can meet simultaneously the requirements of diverse irradiation conditions is a still challenging task. Herein, a low-cost fully non-fused acceptor (denoted as GS60) featuring well-matched absorption spectra with solar, scattered light and artificial light radiation was designed and synthesized. Systematic characterizations revealed that GS60 possessed outstanding photoelectron properties and ideal morphology, which resulted in reduced voltage loss and suppressed charge recombination. By blending with a non-fused ring polymer PTVT-T, the as-obtained GS60 based OPV cells achieved a good power conversion efficiency (PCE) of 14.1 %, a high value for the cells based on non-fused ring bulk heterojunction. Besides, manufactured large-area OPV modules based on PTVT-T:GS60 yielded PCEs of 11.2 %, 11.8 %, 12.1 %, 23.1 %, and 20.3 % under irradiation of AM 1.5G, natural light of cloudy weather, natural light in shadow, laser and indoor, respectively. The PTVT-T:GS60 devices exhibited considerable potential in terms of improving photostability and reducing material cost. Overall, this work provides novel insight into the molecular design of low-cost non-fused ring acceptors, and extended potential of medium band gap acceptors based OPV cells used in various application scenarios.

Design of a Fully Non-Fused Bulk Heterojunction toward Efficient and Low-Cost Organic Photovoltaics

To modulate the miscibility between donor and acceptor materials both possessing fully non-fused ring structures, a series of electron acceptors (A4T-16, A4T-31 and A4T-32) with different polar functional substituents were synthesized and investigated. The three acceptors show good planarity, high conformational stability, complementary absorption and energy levels with the non-fused polymer donor (PTVT-BT). Among them, A4T-32 possesses the strongest polar functional group and shows the highest surface energy, which facilitates morphological modulation in the bulk heterojunction (BHJ) blend. Benefiting from the proper morphology control method, an impressive power conversion efficiency (PCE) of approaching 16.0 % and a superior fill factor over 0.795 are achieved in the PTVT-BT : A4T-32-based organic photovoltaic cells with superior photoactive materials price advantage, which represent the highest value for the cells based on the non-fused blend films. Notably, this cell maintains ≈84 % of its initial PCE after nearly 2000 h under the continuous simulated 1-sun-illumination. In addition, the flexible PTVT-BT : A4T-32-based cells were fabricated and delivered a decent PCE of 14.6 %. This work provides an effective molecular design strategy for the non-fused non-fullerene acceptors (NFAs) from the aspect of bulk morphology control in fully non-fused BHJ layers, which is crucial for their practical applications.