Performance improvement of P3HT nanowire-based organic solar cells by interfacial morphology engineering

Abstract

Poly (3-hexylthiophene-2,5-diyl) nanowires (nw-P3HT) have been a great interest for organic electronics, including organic field-effect transistors, organic photodetectors, organic photovoltaics, etc due to easy formation in the solution process. Thus both explanations of charge transport dynamics and morphology are crucial for device performance. Here we demonstrated the optoelectronic properties of the P3HT nanowires where the polymer backbones were parallel to the nanowire axis. The nanowires tended to form a bundle due to van der Waals interactions. Nanowire bundles were separated by 1,8-diiodooctane (DIO) additive for photovoltaic fabrication. The bundle separation was visualized by atomic force microscopy. The charge transfer mechanism was evaluated by electrochemical impedance spectroscopy. The electrical analysis showed that short-circuit current density (J sc) increases to 10.74 mA cm−2 after the bundle separation. According to impedance analysis, there is a correlation between effective lifetime and DIO ratio. These findings were considered as promising results for improving the transport by forming pathways for charge carriers.

Effects of Thin Film Morphology of Polymer Hole Transfer Material on Photovoltaic Performance of Perovskite Solar Cells

“…However, in the solid phase, since the chain length change of the polymers leads to changes in the morphology of the thin films, it also directly affects the charge transfer processes. Thin-film morphology directly influences charge transport and interfacial charge transfer processes [24].…”

“…The weak solvent interacts with the alkyl chains of P3HT after the addition, reducing the vibrational motion of the chains and allowing π-orbitals of neighbouring polymers to overlap with its own π-orbitals. After that, π-π stacking takes place along the entire chain and forms the nanowire structure [24]. Although nanowire formation causes a redshift in the absorption spectrum, its more dominant effect in device applications is due to the film morphology.…”

“…It is thought that the increase in the short-circuit current and filling factor in the devices produced with UZ-P3HT nanowires is due to the mentioned changes in the nanowire morphology. While the nanowires forming the HTM layer increase the amount of contact at the perovskite-HTM interface, on the other hand, the charge transport within the HTM layer increases thanks to the nano-wire structure [24].…”

“…It has been reported that a smooth morphology is obtained with chain lengths over 85,000D used in the active layer in OSC applications, while the morphology is impaired and the charge transport decreases with shorter chain lengths [20], [23]. For PSC applications where P3HT is used as HTM, studies on PCE changes depending on chain length have been carried out, and it has been reported that higher yields are achieved with an increase in chain length [24]. On the other hand, to increase the charge carrying capacity of P3HT, which has mobility of 0.1 cm 2 V −1 s −1 , and to extend the absorption band, converting it into a nanowire is a method used in the literature.…”

“…On the other hand, to increase the charge carrying capacity of P3HT, which has mobility of 0.1 cm 2 V −1 s −1 , and to extend the absorption band, converting it into a nanowire is a method used in the literature. In OSC applications with nanowire P3HTs, which were grown by optimizing solvent polarity, temperature and time parameters, a mobility of 1.44 m 2 V -1 s -1 and a PCE of 2.40% were achieved [24].…”