Understanding Solvent Manipulation of Morphology in Bulk-Heterojunction Organic Solar Cells.
Film morphology greatly influences the performance of bulk-heterojunction (BHJ)-structure-based solar cells. It is known that an interpenetrating bicontinuous network with nanoscale-separated donor and acceptor phases for charge transfer, an ordered molecular packing for exciton diffusion and charge transport, and a vertical compositionally graded structure for charge collection are prerequisites for achieving highly efficient BHJ organic solar cells (OSCs). Therefore, control of the morphology to obtain an ideal structure is a key problem. For this solution-processing BHJ system, the solvent participates fully in film processing. Its involvement is critical in modifying the nanostructure of BHJ films. In this review, we discuss the effects of solvent-related methods on the morphology of BHJ films, including selection of the casting solvent, solvent mixture, solvent vapor annealing, and solvent soaking. On the basis of a discussion on interaction strength and time between solvent and active materials, we believe that the solvent-morphology-performance relationship will be clearer and that solvent selection as a means to manipulate the morphology of BHJ films will be more rational.
Beijing National Laboratory of Molecular Science, CAS Key Laboratory of Photochemistry, Institution of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.
Yuxia
Y
Chen
Beijing National Laboratory of Molecular Science, CAS Key Laboratory of Photochemistry, Institution of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China. clzhan@iccas.ac.cn.
Chuanlang
http://orcid.org/0000-0001-5127-0973
C
Zhan
Beijing National Laboratory of Molecular Science, CAS Key Laboratory of Photochemistry, Institution of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China. jnyao@iccas.ac.cn.
Jiannian
J
Yao
charge transfer; energy conversion; morphology; solar cells; solvent effects