Synergistic Effects of Binary-Solvent Annealing for Efficient Polymer-Fullerene Bulk Heterojunction Solar Cells.
Conjugated polymer-fullerene-based bulk-heterojunction (BHJ) organic solar cells (OSCs) have attracted tremendous attention over the past two decades because of their potential to develop low-cost and easy methods to produce energy from light. The complicated microstructure and morphology with randomly organized architecture of these polymer-fullerene-based active layers (ALs) is a key factor that limits photovoltaic performance. In this study, a binary-solvent annealing (BSA) approach was established to improve the poly(3-hexylthiophene):indene-C60 bisadduct-based AL for efficient BHJ-type OSCs by varying the second solvents with different boiling points (BP). Thus, we were able to change the evaporation behavior of cosolvents and consequently obtain the various microstructural properties of the AL. An in-depth study was conducted on the solvent-evaporation driven morphology of the active layer under various cosolvent conditions and its effect on the photovoltaic parameters of OSCs. Under the BSA processes, we found that the specimens with low-BP second solvents allows us to observe a more ideal AL for increasing photon absorption and efficient charge transport and collection at the respective electrodes, resulting in enhanced PCE of the corresponding OSCs. By contrast, the specimens with high-BP second solvents exhibit random microstructures, which are detrimental to charge transport and collection and lead to diminished PCE of the corresponding OSCs. By appropriately selecting the composition of a binary solvent, BSA can be employed as an easy method for the effective manipulation of the microstructures of ALs. BSA is a promising technique for the performance enhancement of not only OSCs but also other organic/polymeric-based electronic devices.
Department of Photonics, Advanced Optoelectronic Technology Center, National Cheng Kung University , Tainan 701, Taiwan.
Fu-Chiao
FC
Wu
Department of Photonics, Advanced Optoelectronic Technology Center, National Cheng Kung University , Tainan 701, Taiwan.
Yi-Hao
YH
Li
Department of Photonics, Advanced Optoelectronic Technology Center, National Cheng Kung University , Tainan 701, Taiwan.
Chieh-Jen
CJ
Tsou
Department of Photonics, Advanced Optoelectronic Technology Center, National Cheng Kung University , Tainan 701, Taiwan.
Kuo-Cheng
KC
Tung
Department of Photonics, Advanced Optoelectronic Technology Center, National Cheng Kung University , Tainan 701, Taiwan.
Chia-Te
CT
Yen
Department of Photonics, Advanced Optoelectronic Technology Center, National Cheng Kung University , Tainan 701, Taiwan.
Fang-Sheng
FS
Chou
Department of Physics, National Cheng Kung University , Tainan 701, Taiwan.
Fu-Ching
FC
Tang
Department of Photonics, Advanced Optoelectronic Technology Center, National Cheng Kung University , Tainan 701, Taiwan.
Wei-Yang
WY
Chou
Department of Materials Science and Engineering, National Cheng Kung University , Tainan 701, Taiwan.
Jrjeng
J
Ruan
Department of Photonics, Advanced Optoelectronic Technology Center, National Cheng Kung University , Tainan 701, Taiwan.
Horng-Long
HL
Cheng
atomic force microscopy; cosolvents; indene-C60 bisadduct; morphology; organic solar cells; poly(3-hexylthiophene); spectroscopy