Tuning the Crystallinity and Phase Separation by Two‐Step Annealing Enables Block Copolymer‐Based Organic Solar Cells with 15% Efficiency

Abstract

Organic Solar Cells In article number http://doi.wiley.com/10.1002/solr.202200617, Tao Yang, Teng Zhang, Bingsuo Zou, Tao Liu, and co‐workers applied a two‐step annealing method in which solvent vapor annealing and thermal annealing are included, and successfully achieved 15% efficiency for block copolymer‐based or single‐component organic solar cells. This two‐step annealing also pushes the non‐halogenated solvent dissolved binary all‐polymer solar cells towards > 17% efficiency.

Effect of 1‐Fluoro‐2‐iodobenzene Solvent Additive on the Crystallization of Donors and Acceptors, and Ultrafast Carrier Dynamics in Polymer Solar Cells

“…[ 18–26 ] The purity and crystallinity of the donor‐ and acceptor‐rich domains substantially influence the nanostructure of the BHJ, and consequently, the device performance. [ 27–30 ] Although these morphological features could enable sufficient donor/acceptor interfaces for exciton dissociation, they also introduce overmixed donor/acceptor phases into the active layer, which could hamper charge transport and collection during PSC operation, resulting in undesired charge recombination and preventing a further increase in PSCs performance. [ 31–33 ] Morphology control strategies, [ 34 ] such as thermal and vapor annealing, [ 35–37 ] hot‐substrate casting, [ 38 ] and additive modulation, [ 16,39–42 ] have proven to be effective and essential methods for achieving high PCEs.…”

High Miscibility‐Induced Reduction of Trap Density in All‐Polymer Solar Cells Using Hybrid Cyclohexyl‐Hexyl Side Chains

“…[7][8][9][10][11][12][13][14][15][16] Specifically, the D and A should not only have a certain miscibility to provide sufficient interfaces for exciton dissociation, but also own suitable crystallinity and phase purity and further construct a bicontinuous interpenetrating network structure to improve the hole and electron transport. [9,11,[17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] However, bicontinuous interpenetrating networks with pure individual donor and acceptor phases are difficult to obtain from semicrystalline polymer blends with distinct disorder, which throws the morphological control work into a dilemma in All-PSCs. Moreover, large trap states and localized electronic states in the forbidden gap of semiconductors can be induced by relatively poor blend morphology, acting as recombination centers, lower the mobility, disturb the internal field distribution, and reduce device performance.…”