Effectiveness of External Electric Field Treatment of Conjugated Polymers in Bulk-Heterojunction Solar Cells.
External electric field treatment (EFT) on P3HT:PCBM bulk heterojunction (BHJ) devices was recently found to be a viable approach for improving the power conversion efficiencies (PCEs) through modulating the blend nanomorphology. However, its effectiveness over the broad family of polymer-fullerene blends remains unclear. Herein, we investigate the effects of external EFT on various polymer-fullerene blends with distinct morphologies stemming from the difference in molecular structure of the polymers (i.e., semicrystalline vs amorphous) in a bid to establish a clear morphology-function-charge dynamics relationship to the photovoltaic performance. Our findings reveal that EFT promotes self-organization of the semicrystalline thiophene-based conjugated polymers (i.e., P3HT and P3BT) while it was ineffective for the amorphous polymers (i.e., PTB7 and PCPDTBT) even at the maximum applied E-field of 8 kV cm-1. Transient absorption spectroscopy shows an improvement in the initial charge-carrier and polaron formation from delocalized excitons in the E-field treated semicrystalline blends compared to their untreated reference samples. Interfacial trap-assisted monomolecular and trap-free bimolecular recombination at nanosecond-microsecond time scale in the E-field treated P3BT:PC60BM devices are significantly suppressed. Importantly, our findings shed new light and provide guidelines on the effectiveness of utilizing external EFT to enhance the PCEs of a larger family of conjugated polymer-based BHJ OSCs.
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, Singapore 637371.
Ankur
A
Solanki
Department of Physics, Indian Institute of Technology Kanpur , Kanpur 208016, India.
Anirban
A
Bagui
State Key Laboratory and Institute of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) , Tianjin 300071, China.|School of Materials Science and Engineering, Nankai University , Tianjin 300071, China.
Guankui
G
Long
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, Singapore 637371.
Bo
B
Wu
School of Materials Science and Engineering, Nanyang Technological University , 50 Nanyang Avenue, Singapore 639798.
Teddy
T
Salim
State Key Laboratory and Institute of Elemento-Organic Chemistry, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin) , Tianjin 300071, China.|School of Materials Science and Engineering, Nankai University , Tianjin 300071, China.
Yongsheng
Y
Chen
School of Materials Science and Engineering, Nanyang Technological University , 50 Nanyang Avenue, Singapore 639798.|Energy Research Institute @ NTU (ERI@N) , 1 CleanTech Loop, #06-04 CleanTech One, Singapore 637141.
Yeng Ming
YM
Lam
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University , 21 Nanyang Link, Singapore 637371.|Energy Research Institute @ NTU (ERI@N) , 1 CleanTech Loop, #06-04 CleanTech One, Singapore 637141.
Tze Chien
TC
Sum
bulk heterojunction solar cell; electric dipole moment; external electric field treatment; morphology and transient absorption spectroscopy