10.1002/chem.201705140
Chemistry - A European Journal
FULL PAPER
HRMS (ESI-TOF) m/z : [M + H]+ Calcd. for C39H41O6N2, 633.2959; found,
633.2971.
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Device fabrication
The BHJ cells bearing USQ:PC71BM photoactive layer were fabricated as
follow: patterned indium-tin-oxide (ITO) coated glass substrates were
cleaned using detergent, deionized water, acetone and isopropanol in
sequence in an ultrasonic bath. Cleaned substrates were dried and kept
in an oven at 80 ºC and exposed to UV ozone for 30 min, and then were
immediately transferred into a high-vacuum chamber (1 × 10−5 Pa) for the
deposition of 6 nm MoO3 thin layer. Photoactive layers with thickness of
70 ± 5 nm were fabricated by spin-coating USQ:PC71BM solution (20 mg
mL−1 in chloroform) on the MoO3 pre-coated ITO substrates in a N2-filling
glove box, followed by additional thermal treatment at 70 ºC for 10 min.
Finally, the substrates were transferred back to a high-vacuum chamber
where 8-hydroxyquinolatolithium (Liq, 1 nm) and Al (100 nm) were
deposited as the top electrode. Liq and MoO3 were used as the n- and p-
type interfacial layers, respectively. The active area of each cell is 0.04
cm2 defined by the overlap of the ITO anode and the Al cathode. The
final device structure was ITO/MoO3 (6 nm) /USQ:PC71BM (70 ± 5 nm)
/Liq (1 nm) /Al (100 nm). To obtain the average data related to device
performance, two batches of devices (6 cells per batch) for each set of
conditions were fabricated and tested. In addition, the SCLC (space-
charge-limited-current) model was employed to characterize the carrier
mobilities in the blend films, and hole-only devices were fabricated with a
structure of ITO/MoO3 (6 nm) /USQ:PC71BM (70 nm, 1:3 in wt%) /MoO3
(6 nm) /Al.
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Acknowledgements
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We acknowledge the financial support for this work from the
National Natural Science Foundation of China (project
No.51573108, 61604093, 21372168), the Natural Science
Foundation of Shanghai (16ZR1411000) and the Shanghai
Pujiang Program (16PJ1403300). We also would like to thank Dr.
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Keywords: Unsymmetrical squaraine (USQ) 1 • hydroxyl
substituent 2 • hole mobility 3 • bulk heterojunction (BHJ)
photovoltaic cells 4
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