The isotopic effects of deuteration on optoelectronic properties of conducting polymers

Abstract

The attractive optoelectronic properties of conducting polymers depend sensitively upon intra-and inter-polymer chain interactions, and therefore new methods to manipulate these interactions are continually being pursued. Here, we report a study of the isotopic effects of deuterium substitution on the structure, morphology and optoelectronic properties of regioregular poly(3-hexylthiophene)s with an approach that combines the synthesis of deuterated materials, optoelectronic properties measurements, theoretical simulation and neutron scattering. Selective substitutions of deuterium on the backbone or side-chains of poly(3-hexylthiophene)s result in distinct optoelectronic responses in poly(3-hexylthiophene)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) photovoltaics. Specifically, the weak non-covalent intermolecular interactions induced by the main-chain deuteration are shown to change the film crystallinity and morphology of the active layer, consequently reducing the short-circuit current. However, side-chain deuteration does not significantly modify the film morphology but causes a decreased electronic coupling, the formation of a charge transfer state, and increased electron-phonon coupling, leading to a remarkable reduction in the open circuit voltage.

Nanophase Engineering of Organic Semiconductor-Based Solar Cells

“…The GIWAXS profiles from both non-deuterated and deuterated blend films show the out-of-plane diffraction patterns ) show the selected area electron diffraction patterns. Reprinted with permission from Shao et al [84]. © (2014) Nature Publishing Group of (l00) reflections and the in-plane (010) reflection patterns, indicating a well-organized lamellar structure with edge-on orientation on the substrate.…”

“…7.11 a Chemical structure of P3HT, MD-P3HT, and SD-P3HT; J-V curves under illumination of 100 mW/cm 2 (b) and absorption spectra (c) of the three P3HT isotopes blended with PCBM. Reprinted with permission from Shao et al [84]. © (2014) Nature Publishing Group Shao et al [84] also examined deuteration effect on film morphology and crystallinity of P3HT.…”

“…Reprinted with permission from Shao et al [84]. © (2014) Nature Publishing Group Shao et al [84] also examined deuteration effect on film morphology and crystallinity of P3HT. Nanofibrillar structures were observed in both P3HT/PC 61 BM and SD-P3HT/PC 61 BM films in AFM phase images (Fig.…”

“…However, how isotopic substitution affects the film morphology, phase separation, and optoelectronic properties in OPV devices is still an unresolved question. Shao et al [84] found that selective deuteration on P3HT polymer has a remarkable contribution to the morphology, phase separation, and charge transport properties in OPVs. Figure 7.11a shows the main chain deuteration and side chain deuteration on P3HT polymers.…”

“…Shao et al have investigated the lateral domain morphologies of PC 61 BM dispersed in various P3HT matrices using GISAXS [84], where the in-plane GISAXS profiles (intensity vs. q y ) were modeled using a combined model of Guinier-Porod [85] and polydisperse hard-sphere model with Schulz distribution [86] as shown in Fig. 7.14.…”