有机太阳能电池因其器件结构简单、质轻、柔性和可大面积溶液加工等优点，受到了广泛关注，目前其光电转换效率 (PCE) 已超过了18%，但材料合成的复杂性和较高成本却限制了其商业化的应用。本论文主要从简化分子结构、降低制备成本出发，通过对侧链、π桥和共轭骨架的调控，设计、合成了一系列非稠环电子受体，并系统地研究了受体材料“分子结构-器件性能”之间的关系。具体内容如下：

一、通过在非稠环电子受体上引入富勒烯受体作为侧链，设计合成了两种新型杂化电子受体材料PC₆₁BM-C6和PC₆₁BM-C10，系统地研究了PC₆₁BM作为侧链对受体分子性能的影响。结果表明PC₆₁BM的引入可以有效调控受体分子的溶解性、吸收和堆积方式。更重要的是，PC₆₁BM作为位阻较大的侧链可以有效抑制受体分子聚集的同时，与聚合物共混形成合适的相分离，并提高了激子的解离效率和电荷收集能力。最终，含PC₆₁BM侧链的受体分子PC₆₁BM-C6和PC₆₁BM-C10展现了更加优异的光伏性能，其中，基于PBDB-T:PC₆₁BM-C10器件的PCE高达13.55% (V_oc = 0.87 V，J_sc = 21.30 mA/cm²，FF = 72.66%)。

二、设计合成了一系列以二噻吩并环戊二烯为中心核，含不同取代基的噻吩为π桥，结构简单的A-π-D-π-A型非稠环电子受体CPDT-O_iT-4F，CPDT-O_oT-4F和CPDT-2OT-4F，三种受体分子的π桥分别为：内侧单烷氧基取代的噻吩，外侧单烷氧基取代的噻吩，双烷氧基取代的噻吩。研究发现，烷氧基的位置和数量的不同，使受体分子内形成了不同的分子内非共价键相互作用，这可以有效调控分子的平面性，吸收、能级、结晶性和微观形貌。与CPDT-O_iT-4F相比，CPDT-O_oT-4F和CPDT-2OT-4F的吸收蓝移，带隙变宽，LUMO能级提升。GIWAXS结果显示CPDT-O_iT-4F纯膜同时存在着face-on和edge-on的堆积方式，而CPDT-O_oT-4F和CPDT-2OT-4F纯膜主要呈现face-on的堆积方式。与聚合物PBDB-T共混后，基于CPDT-O_oT-4F和CPDT-2OT-4F的共混膜均形成了良好的相分离尺度，最终光伏器件展现了较低的非辐射能量损失 (0.25和0.24 eV)，其PCE分别为10.02%和10.58%，远高于CPDT-O_iT-4F的PCE (5.80%)。

三、为考察不同π桥及杂原子对器件性能的影响，设计并合成了二噻吩并芳杂环单元为中心核，双烷氧基苯为π桥的A-π-D-π-A型非稠环受体CPDT-BO-4F和DTS-BO-4F。研究表明，与CPDT-2OT-4F相比，p桥的改变使分子CPDT-BO-4F分子的吸收蓝移，能级和分子的堆积方式发生了变化。GIWAXS结果显示CPDT-BO-4F纯膜呈现edge-on的堆积方式。此外，对比两个分子CPDT-BO-4F和DTS-BO-4F，桥连原子对分子吸收、能级和结晶性也有显著的影响。其中，CPDT-BO-4F具有较高的摩尔消光系数和结晶性，堆积更加有序。最终，基于PBDB-T:CPDT-BO-4F的共混膜展现了合适的相分离尺度和较高的电荷迁移率，器件具有较低的非辐射能量损失 (0.23 eV)，最终光伏性能可以达到13.26％。

四、有机光伏的商业化应用要求材料易于制备，即具有简单的分子结构，本章以四联噻吩为母核，设计合成了一系列完全非稠环电子受体(4T-1、4T-2、4T-3和4T-4)，这四个分子均以廉价的商业化噻吩衍生物为起始材料，通过两步反应即可高产率的制备。通过侧链工程有效调控了分子吸收、溶解性、堆积方式。其中，受体分子4T-3与给体聚合物PBDB-T和D18均表现出了良好的匹配性，基于D18:4T-3的光伏器件获得了更高的PCE，为12.04%，这也是目前基于完全非稠环受体最高的光伏性能之一。

Organic solar cells (OSCs) have attracted increasing attention owing to some merits such as light weight, low cost, flexibility, and large-area solution processing. Although the power conversion efficiencies (PCEs) of OSCs have exceeded 18%, there are still some problems such as cost of OSCs exist for commercial applications. This dissertation focuses on the molecular design strategies of non-fused ring acceptors (NFRAs) with simplifying molecular structure and low-costs, through the regulation of side chains, π bridges and conjugated skeletons. Then, we systematically study the relationship between chemical structure and photovoltaic performance. The main contents are as follows:

1. Two hybrid electron acceptors (PC₆₁BM-C6 and PC₆₁BM-C10) have been designed and synthesized via the combination of non-fused-ring acceptor DOC2C6-2F and PC₆₁BM. For comparison, acceptor molecule CH₃COO-C6 without the fullerene pendent was also synthesized for control experiments. Compared with CH₃COO-C6, the bulky fullerene pendent could effectively hinder the intermolecular aggregation in thin films and form the preferred blend morphology. The molecular packing patterns changes from face on to isotropic patterns according to the GIWAXS measurements. This strategy significantly improved the efficiencies for exciton separation and charge collection. Finally, the V_oc, J_sc, and FF of PC₆₁BM-C10-based devices were simultaneously improved and an enhanced PCE of 13.55% was accomplished.

2. Three novel A-π-D-π-A NFRAs CPDT-O_iT-4F，CPDT-O_oT-4F and CPDT-2OT-4F have been designed and synthesized, comprising cyclopentadithiophene (CPDT) as the central core and three different alkoxythienyl units as π-spacer. Side chain engineering of the π-spacers have been carefully considered and the variations are the alky chain orientation of the thiophsene π-spacer in the molecule skeleton i.e. inner mono-ethylhexyloxy substitution, outer mono-ethylhexyloxy substitution and bis(ethylhexyloxy) substitution, respectively. The position and number of alkoxy groups can lead to varied non-covalent bond interactions, which can effectively tune the UV-vis absorption, energy levels, crystallinities and microscopic morphologies. Compared with CPDT-O_iT-4F, CPDT-O_oT-4F and CPDT-2OT-4F exhibit relatively blueshifted spectra with higher LUMO energy levels. The neat films of CPDT-O_iT-4F adopt a face-on and edge-on orientation, simultaneously, while the neat films of CPDT-O_oT-4F and CPDT-2OT-4F adopt a face-on orientation. After blending with polymer PBDB-T, the blend films based on CPDT-O_oT-4F and CPDT-2OT-4F formed suitable phase separation morphology, and showed lower non-radiative energy losses (0.25 and 0.24 eV) compared with CPDT-O_iT-4F. PCEs of 10.02% and 10.58% can be acieved, which are much higher than the PCE of 5.80% for CPDT-O_iT-4F.

3. To further study the π-bridge and heteroatom influences on the photovoltaic performances, two novel A-π-D-π-A NFRAs CPDT-BO-4F, and DTS-BO-4F have been designed and synthesized, which comprised of cyclopentadithiophene (CPDT) and dithienosilole (DTS) as the central donor unit flanked with bis(ethylhexyloxy)-substituted benzene units as π-spacer. Compared with CPDT-2OT-4F, CPDT-BO-4F exhibit relatively blueshifted spectra with a higher LUMO energy level, which is conducive to obtain a high V_oc. The neat film of CPDT-BO-4F adopts an edge-on orientation. In addition, compared with DTS-BO-4F, CPDT-BO-4F possesses higher molar extinction coefficient, stronger crystallinity and more orderly stacking. Finally, the blend film based on PBDB-T:CPDT-BO-4F showed suitable phase separation scale and high electron mobility, a high PCE of 13.26% and low non-radiative energy loss of 0.23 eV can be achieved.

4. To meet the commercialization requirements for simplifying the material preparation, we have developed a series of tetrathiophene-based fully non-fused electron acceptors (FNEAs) 4T-1, 4T-2, 4T-3, and 4T-4, which were synthesized in high yields using commercially available thiophene derivatives as the starting materials. Tailoring the size of lateral chains can tune the solubility and packing mode of acceptor molecules in neat and blend films. We found that incorporation of 2-ethylhexyl chains can effectively change the compatibility with the donor polymer PBDB-T, and an encouraging PCE of 10.15% was accomplished by 4T-3-based organic solar cells. It also presents good compatibility with the other polymer donor and an even higher PCE of 12.04% was achieved based on D18:4T-3 blend, which is one of the highest PCE for the fully non-fused acceptors.