TY - JOUR
T1 - High-efficiency nonfullerene organic solar cells
T2 - critical factors that affect complex multi-length scale morphology and device performance
AU - Ye, Long
AU - Zhao, Wenchao
AU - Li, Sunsun
AU - Mukherjee, Subhrangsu
AU - Carpenter, Joshua H.
AU - Awartani, Omar
AU - Jiao, Xuechen
AU - Hou, Jianhui
AU - Ade, Harald
PY - 2017/4/5
Y1 - 2017/4/5
N2 - Organic solar cells (OSCs) made of donor/acceptor bulk-heterojunction active layers have been of widespread interest in converting sunlight to electricity. Characterizing of the complex morphology at multiple length scales of polymer:nonfullerene small molecular acceptor (SMA) systems remains largely unexplored. Through detailed characterizations (hard/soft X-ray scattering) of the record-efficiency polymer:SMA system with a close analog, quantitative morphological parameters are related to the device performance parameters and fundamental morphology–performance relationships that explain why additive use and thermal annealing are needed for optimized performance are established. A linear correlation between the average purity variations at small length scale (≈10 nm) and photovoltaic device characteristics across all processing protocols is observed in ≈12%-efficiency polymer:SMA systems. In addition, molecular interactions as reflected by the estimated Flory–Huggins interaction parameters are used to provide context of the room temperature morphology results. Comparison with results from annealed devices suggests that the two SMA systems compared show upper and lower critical solution temperature behavior, respectively. The in-depth understanding of the complex multilength scale nonfullerene OSC morphology may guide the device optimization and new materials development and indicates that thermodynamic properties of materials systems should be studied in more detail to aid in designing optimized protocols efficiently.
AB - Organic solar cells (OSCs) made of donor/acceptor bulk-heterojunction active layers have been of widespread interest in converting sunlight to electricity. Characterizing of the complex morphology at multiple length scales of polymer:nonfullerene small molecular acceptor (SMA) systems remains largely unexplored. Through detailed characterizations (hard/soft X-ray scattering) of the record-efficiency polymer:SMA system with a close analog, quantitative morphological parameters are related to the device performance parameters and fundamental morphology–performance relationships that explain why additive use and thermal annealing are needed for optimized performance are established. A linear correlation between the average purity variations at small length scale (≈10 nm) and photovoltaic device characteristics across all processing protocols is observed in ≈12%-efficiency polymer:SMA systems. In addition, molecular interactions as reflected by the estimated Flory–Huggins interaction parameters are used to provide context of the room temperature morphology results. Comparison with results from annealed devices suggests that the two SMA systems compared show upper and lower critical solution temperature behavior, respectively. The in-depth understanding of the complex multilength scale nonfullerene OSC morphology may guide the device optimization and new materials development and indicates that thermodynamic properties of materials systems should be studied in more detail to aid in designing optimized protocols efficiently.
KW - coherence length
KW - interaction parameters
KW - nonfullerene acceptors
KW - organic solar cells
KW - purity
UR - http://www.scopus.com/inward/record.url?scp=85006728507&partnerID=8YFLogxK
U2 - 10.1002/aenm.201602000
DO - 10.1002/aenm.201602000
M3 - Article
AN - SCOPUS:85006728507
SN - 1614-6832
VL - 7
JO - Advanced Energy Materials
JF - Advanced Energy Materials
IS - 7
M1 - 1602000
ER -