### 基于非富勒烯受体的溶液加工型全小分子太阳能电池研究进展

• 收稿日期:2018-02-26 发布日期:2018-04-17
• 通讯作者: 何畅,侯剑辉 E-mail:hechang@iccas.ac.cn;hjhzlz@iccas.ac.cn
• 作者简介:何畅，中国科学院化学研究所副研究员。2007年6月毕业于中国科学院化学研究所，获理学博士学位。长期从事溶液可加工有机光伏材料设计与器件研究工作|侯剑辉，中国科学院化学研究所研究员，博士生导师。2006年6月毕业于中国科学院化学研究所，获理学博士学位。长期从事有机光伏领域的研究，研究方向包括新型有机光伏材料的设计合成以及高效率有机光伏器件的制备技术等
• 基金资助:
国家自然科学基金(521734008)

### Advances in Solution-Processed All-Small-Molecule Organic Solar Cells with Non-Fullerene Electron Acceptors

Chang HE*(),Jianhui HOU*()

• Received:2018-02-26 Published:2018-04-17
• Contact: Chang HE,Jianhui HOU E-mail:hechang@iccas.ac.cn;hjhzlz@iccas.ac.cn
• Supported by:
the National Natural Science Foundation of China(521734008)

Abstract:

Solution-processed bulk-heterojunction organic solar cells (BHJ-OSCs), with their advantages of light weight, low cost, and easy fabrication, are a photovoltaic technology with practical potentials. In BHJ-OSCs, the exciton dissociation and charge transport are highly sensitive to the molecular packing pattern and phase separation morphology in the active layer. On the other hand, when using photovoltaic small molecules (SMs), the purity can be controlled due to their well-defined chemical structure, and therefore there is better reproducibility in device performance. Especially, the non-fullerene acceptors are easier to tune in their light absorption and energy level. Hence, there has been considerable interest in small non-fullerene SM organic solar cells (NF-SM-OSCs). Although these cells have the dual advantages of non-fullerene acceptor materials and SMs, the fabrication of high-efficiency cells still possess great challenges. For example, efficient photovoltaic SMs typically possess an acceptor-donor-acceptor (A-D-A) structure that causes intrinsic anisotropy, making it more complicated to modulate and control the morphology of the nanoscale active layer. In this article, we will summarize recent advances in high-performance NF-SM-OSCs, and present an introduction of the specific requirements for SM donors in the small NF-SM-OSCs. We first summarize our works on SM donors with the A-D-A structure. The trialkylthienyl-substituted benzodithiophene (TriBDT-T) unit is employed as the D-core unit, and the A end groups include rhodanine (RN), cyano-rhodanine (RCN), and 1, 3-indanone (IDO). The band gap (Eg) of these compounds is about 2.0 eV, with the low-lying highest occupied molecular orbital (HOMO) level of -5.51 eV. First, NF-SM-OSCs with DRTB-T and a non-fullerene acceptor (IDIC) were constructed. The morphology of the active layer was fine-tuned by solvent vapor annealing (SVA), leading to the formation of the desired interconnected nanoscale structure. Our results demonstrate that the molecular design of a wide band gap (WBG) donor to create a well-matched donor-acceptor pair with a low band gap (LBG) non-fullerene SM acceptor, as well as subtle morphological control, provides great potential to realize high-performance NFSM-OSCs. We also studied the molecular orientation optimization from the aspect of molecular design. We designed and synthesized a group of SM compounds having identical π-conjugated backbones and end groups with different alkyl chain lengths. Since these compounds have identical photoelectric properties, they allow us to focus on the significant influence of the end alkyl chains on the molecular orientation and intermolecular aggregation behavior in solid-state films. Characterization of the DRTB-T-CX films using 2D grazing incidence wide-angle X-ray scattering (GIWAXS) revealed an obvious transition of orientation from edge-on to face-on relative to the substrate when the end alkyl chain is lengthened. This demonstrates that the length of the end alkyl chain can be used to modify the molecular orientation. A DRTB-T-C4/IT-4F-based device achieved a maximum power conversion efficiency (PCE) of up to 11.24%, which is the best performance reported for state-of-the-art NF-SM-OSCs. On this basis, the challenges and prospects of NF-SM-OSCs are discussed.

MSC2000:

• O646