Influence of 3D morphology on the performance of all-polymer solar cells processed using environmentally benign nonhalogenated solvents

Hyeseung Jung, A. Ra Jung, Seon Mi Jin, Seah Kim, Hyojung Heo, Hoai Van T. Nguyen, Min Je Kim, Pyeongkang Ahn, Myung Hwa Kim, Youngu Lee, Kyung Koo Lee, Jeong Ho Cho, Eunji Lee, Bong Soo Kim

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12 Scopus citations


Advancing the photovoltaic performance of all-polymer solar cells (APSCs) requires a comprehensive understanding of the dependence of the properties of photoactive blend films on the solvents used to process them. We have studied the correlation between the morphology of PTB7-Th:PNDI2OD-T2 blend films prepared using six different processing solvents. Three-dimensional (3D) transmission electron microscopy tomography (TEMT) revealed the influence of the 3D morphology of the PTB7-Th:PNDI2OD-T2 blend films on their photovoltaic performance. The high-performing toluene (TOL)- and o-xylene (XY)-processed blend films displayed power conversion efficiencies (PCEs) of ~4%, which contained nanoscopically networked fibrous PNDI2OD-T2 polymer domains. The films processed using the other solvents exhibited partly disconnected domains or unfavorable vertical phase separation. In addition, the use of N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), or N-methyl-2-pyrrolidone (NMP) as a solvent additive in XY solution resulted in a substantial improvement in the PCEs to 6.1%. This large enhancement was attributed to the formation of the better-interconnected narrower crystalline fibrillary structure of PNDI2OD-T2 chains with the aid of solvent additives, as clearly elucidated by 3D-TEMT imaging. This work highlights that APSCs processed from benign nonhalogenated solvents with appropriate additives can outperform APSCs processed from toxic halogenated solvents by affording a favorable blend morphology and that 3D TEMT imaging is a powerful and essential tool for characterizing the true morphology of photoactive layers.

Original languageEnglish
Article number105106
JournalNano Energy
StatePublished - Nov 2020

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© 2020 Elsevier Ltd


  • Active layer morphology
  • All-polymer solar cell
  • Environmentally benign solvent/additive
  • Molecular dynamics simulation
  • TEM tomography


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