Wang Li-Ming, Li Qingduan, Liu Shengjian, Cao Zhixiong, Cai Yue-Peng, Jiao Xuechen, Lai Haojie, Xie Weiguang, Zhan Xiaozhi, Zhu Tao
Institute of High Energy Physics, Chinese Academy of Sciences (CAS), Beijing 100049, China.
Spallation Neutron Source Science Center, Dongguan 523803, China.
ACS Appl Mater Interfaces. 2020 May 27;12(21):24165-24173. doi: 10.1021/acsami.0c02843. Epub 2020 May 16.
The vertical component distribution of bulk heterojunction (BHJ) active film shows a significant impact on determining the device performance in polymer solar cells (PSCs). Processing solvent additives are well known for regulating the BHJ active layer morphology; however, there are few reports regarding the quantitative evaluation of the effect. Herein, a study of the quantitative determination of the vertical segregation in combination of molecular ordering of PBDB-T/ITIC blend films with various 1,8-diiodooctane (DIO) contents is provided. A 0.5% (volume ratio) DIO-added blend film achieves the highest power conversion efficiency of 10.75%. The reduced performance of the PSCs resulted from the excessive vertical component segregation and overcrystallization investigated by various techniques. X-ray photoelectron spectroscopy indicates that DIO aggravates the PBDB-T enrichment region at the air side. Neutron reflectivity further quantitatively figures out the phase separation effect. Although increased crystallinity of ITIC and a higher face-on ratio of PBDB-T in active layer were obtained with increased DIO content approved by grazing-incidence wide-angle X-ray scattering (GIWAXS), the enhanced vertical distribution along with the enhanced crystal size of ITIC leads to the reduced performance of the PSCs due to the reduced carrier transportation paths between donor and acceptor.
本体异质结（BHJ）活性薄膜的垂直组分分布对聚合物太阳能电池（PSC）的器件性能有着显著影响。加工溶剂添加剂常用于调节BHJ活性层的形态；然而，关于其效果定量评估的报道却很少。在此，我们对不同1,8 - 二碘辛烷（DIO）含量的PBDB - T/ITIC共混薄膜的分子有序性与垂直偏析定量测定进行了研究。添加0.5%（体积比）DIO的共混薄膜实现了10.75%的最高功率转换效率。通过多种技术研究发现，PSC性能的降低是由于过度的垂直组分偏析和过度结晶所致。X射线光电子能谱表明，DIO加剧了空气侧PBDB - T的富集区域。中子反射率进一步定量地揭示了相分离效应。尽管掠入射广角X射线散射（GIWAXS）证实，随着DIO含量的增加，活性层中ITIC的结晶度提高且PBDB - T的面内取向比例更高，但由于供体和受体之间载流子传输路径的减少，ITIC增强的垂直分布以及增大的晶体尺寸导致了PSC性能的降低。
