Ternary Polymer Solar Cells Facilitating Improved Efficiency and Stability

The use of a ternary active layer offers a promising approach to enhance the power conversion efficiency (PCE) of polymer solar cells (PSCs) via simply incorporating a third component. Here, a ternary PSC with improved efficiency and stability facilitated by a new small molecule IBC‐F is demonstrated. Even though the PBDB‐T:IBC‐F‐based device gives an extremely low PCE of only 0.21%, a remarkable PCE of 15.06% can be realized in the ternary device based on PBDB‐T:IE4F‐S:IBC‐F with 20% IBC‐F, which is ≈10% greater than that (PCE = 13.70%) of the control binary device based on PBDB‐T:IE4F‐S. The improvement in the device performance of the ternary PSC is mainly attributed to the enhancement of fill factor, which is due to the improved charge dissociation and extraction, suppressed bimolecular and trap‐assisted recombination, longer charge‐carrier lifetime, and enhanced intermolecular interactions for preferential face‐on orientation. Additionally, the ternary device with 20% IBC‐F shows better thermal and photoinduced stability over the control binary device. This work provides a new angle to develop the third components for building ternary PSCs with enhanced photovoltaic performance and stability for practical applications.     

新型窄带隙聚合物太阳能电池光伏材料

聚合物太阳能电池中给体材料的能级水平、带隙、光吸收系数、溶解性、成膜性及载流子迁移率是决定器件性能的关键因素.阐述了聚合物太阳能电池中给体材料的最新研究进展,着重介绍了含有苯并双噻吩的窄带隙D-A类型的共聚物,并对一些给体材料的能级水平优化结果做了简单的总结.最后指出了未来聚合物太阳能电池给体材料今后的发展方向.     

Quadruple Junction Polymer Solar Cells with Four Complementary Absorber Layers

A monolithic two‐terminal solution‐processed quadruple junction polymer solar cell in an n–i–p (inverted) configuration with four complementary polymer:fullerene active bulk‐heterojunction layers is presented. The subcells possess different optical bandgaps ranging from 1.90 to 1.13 eV. Optical modeling using the transfer matrix formalism enables prediction of the fraction of absorbed photons from sunlight in each subcell and determine the optimal combination of layer thicknesses. The quadruple junction cell features an open‐circuit voltage of 2.45 V and has a power conversion efficiency of 7.6%, only slightly less than the modeled value of 8.2%. The external quantum efficiency spectrum, determined with appropriate light and voltage bias conditions, exhibits in general an excellent agreement with modeled spectrum. The device performance is presently limited by bimolecular recombination, which prevents using thick photoactive layers that could absorb light more efficiently.     

Understanding Low Bandgap Polymer PTB7 and Optimizing Polymer Solar Cells Based on It

Solution processed single junction polymer solar cells (PSCs) have been developed from less than 1% power conversion efficiency (PCE) to beyond 9% PCE in the last decade. The significant efficiency improvement comes from progress in both rational design of donor polymers and innovation of device architectures. Among all the novel high efficient donor polymers, PTB7 stands out as the most widely used one for solar cell studies. Herein the recent development of PTB7 solar cells is reviewed. Detailed discussion of basic property, structure property relationship, morphology study, interfacial engineering, and inorganic nanomaterials incorporation is provided. Possible future directions for further increasing the performance of PTB7 solar cells are discussed.