TY - JOUR
T1 - Miscibility–Function Relations in Organic Solar Cells
T2 - Significance of Optimal Miscibility in Relation to Percolation
AU - Ye, Long
AU - Collins, Brian A.
AU - Jiao, Xuechen
AU - Zhao, Jingbo
AU - Yan, He
AU - Ade, Harald
PY - 2018/10/5
Y1 - 2018/10/5
N2 - Polymer solar cells (PSCs) continue to be a promising low-cost and lead-free photovoltaic technology. Of critical importance to PSCs is understanding and manipulating the composition of the amorphous mixed phase, which is governed by the thermodynamic molecular interactions of the polymer donor and acceptor molecules and the kinetics of the casting process. This progress report clarifies and defines nomenclature relating to miscibility and its relevance and implications to PSC devices in light of new developments. Utilizing a scanning transmission X-ray microscopy method, the temperature dependences of “molecular miscibility” in the presence of fullerene crystals, now referred to liquidus miscibility, are presented for a number of representative blends. An emphasis is placed on relating the amorphous miscibility of high-efficiency PSC blends at a given processing temperature with their actual device performance and stability. It is shown and argued that a system with an amorphous miscibility close to percolation exhibits the most stable morphology. Furthermore, an approach is outlined to convert liquidus miscibility to an effective Flory–Huggins interaction parameter χ. Crucially, determination of temperature-dependent amorphous miscibility paves a way to rationally optimize the stability and mixing behaviors of PSCs at actual processing and operating temperatures.
AB - Polymer solar cells (PSCs) continue to be a promising low-cost and lead-free photovoltaic technology. Of critical importance to PSCs is understanding and manipulating the composition of the amorphous mixed phase, which is governed by the thermodynamic molecular interactions of the polymer donor and acceptor molecules and the kinetics of the casting process. This progress report clarifies and defines nomenclature relating to miscibility and its relevance and implications to PSC devices in light of new developments. Utilizing a scanning transmission X-ray microscopy method, the temperature dependences of “molecular miscibility” in the presence of fullerene crystals, now referred to liquidus miscibility, are presented for a number of representative blends. An emphasis is placed on relating the amorphous miscibility of high-efficiency PSC blends at a given processing temperature with their actual device performance and stability. It is shown and argued that a system with an amorphous miscibility close to percolation exhibits the most stable morphology. Furthermore, an approach is outlined to convert liquidus miscibility to an effective Flory–Huggins interaction parameter χ. Crucially, determination of temperature-dependent amorphous miscibility paves a way to rationally optimize the stability and mixing behaviors of PSCs at actual processing and operating temperatures.
KW - miscibility
KW - percolation thresholds
KW - polymer solar cells
KW - scanning transmission X-ray microscopy
UR - http://www.scopus.com/inward/record.url?scp=85054396025&partnerID=8YFLogxK
U2 - 10.1002/aenm.201703058
DO - 10.1002/aenm.201703058
M3 - Article
AN - SCOPUS:85054396025
SN - 1614-6832
VL - 8
JO - Advanced Energy Materials
JF - Advanced Energy Materials
IS - 28
M1 - 1703058
ER -