Journal
ADVANCED MATERIALS
Volume 34, Issue 33, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/adma.202202608
Keywords
all-polymer solar cells; blend morphology; device stability; layer-by-layer deposition; power conversion efficiency
Categories
Funding
- APRC Grant of the City University of Hong Kong [9380086]
- US Office of Naval Research [N000142012155, N00014-20-12191]
- Research Grants Council of Hong Kong [C6023-19GF, 11307621, GHP/018/20SZ]
- Guangdong-Hong Kong-Macao Joint Laboratory of Optoelectronic and Magnetic Functional Materials [2019B121205002]
- National Research Foundation (NRF) of Korea [2016M1A2A2940911, 2020M3H4A3081814]
- Office of Science, Office of Basic Energy Sciences, of the US Department of Energy [DE-AC02-05CH11231]
- Guangdong Major Project of Basic and Applied Basic Research [2019B030302007]
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By leveraging the layer-by-layer (LBL) deposition technique to engineer the morphology of all-polymer blends, optimal molecular orientation, vertical composition distribution, and efficient charge transport and extraction have been achieved, leading to high-performance all-polymer solar cells (all-PSCs).
A major challenge hindering the further development of all-polymer solar cells (all-PSCs) employing polymerized small-molecule acceptors is the relatively low fill factor (FF) due to the difficulty in controlling the active-layer morphology. The issues typically arise from oversized phase separation resulting from the thermodynamically unfavorable mixing between two macromolecular species, and disordered molecular orientation/packing of highly anisotropic polymer chains. Herein, a facile top-down controlling strategy to engineer the morphology of all-polymer blends is developed by leveraging the layer-by-layer (LBL) deposition. Optimal intermixing of polymer components can be achieved in the two-step process by tuning the bottom-layer polymer swelling during top-layer deposition. Consequently, both the molecular orientation/packing of the bottom layer and the molecular ordering of the top layer can be optimized with a suitable top-layer processing solvent. A favorable morphology with gradient vertical composition distribution for efficient charge transport and extraction is therefore realized, affording a high all-PSC efficiency of 17.0% with a FF of 76.1%. The derived devices also possess excellent long-term thermal stability and can retain >90% of their initial efficiencies after being annealed at 65 degrees C for 1300 h. These results validate the distinct advantages of employing an LBL processing protocol to fabricate high-performance all-PSCs.
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