Equilibration and thermal reversibility in mixtures of model OPV small-molecules and polymers

Abstract

The thermal behaviour of small-molecule/polymer mixtures is of crucial significance in relation to the operational stability of organic photovoltaics, and the equilibration (or otherwise) of domain compositions and interfaces is...

Hysteresis in phase volumes, compositions and interfacial roughness in model OPV-small-molecule/polymer thin-films

“…The bottom (close to pure Bis-PCBM) layer SLD, ρ bottom , behaves in a way that is commensurate with reversible thermal expansion/contraction, as the temperature of this sample is cycled from 173 °C to 114 °C and then back to 181 °C, before final cooling to 80 °C (NB: this correspondence to thermal expansion of the bottom layer can only be understood in relation to ρ bottom . As discussed in Higgins et al , 30 d bottom actually reduces with temperature, due to changes in the equilibrium phases that result in mass-transfer of fullerene molecules into the top layer). It can be seen in Fig.…”

“…The blend ratio was such that this layer was initially in the two-phase part of the phase diagram. 27,30 There is considerable, and rapid, change in the reflectivity curve on heating to 139 °C (Fig. 2b).…”

“…In contrast to samples D and E, parameters for samples that were heated straight to 173 °C and then temperature cycled did not show such hysteresis (see Higgins et al . 30 and Fig. S5_2, ESI†).…”

“…As found previously during our studies on PCBM, 27 no evidence of characteristic fullerene oxidation 41 was observed (see Higgins et al . 30 ).…”

Unveiling re-entrant phase behavior and crystalline–amorphous interactions in semi-conducting polymer:small molecule blends

“…Binodals can be measured with small-angle X-ray/neutron scattering/reflectivity 16,17 or time-of-flight secondary ion mass spectrometry (ToF-SIMS). 5,[18][19][20][21] Particularly, a few polymer:SMA blends have been reported with a UCST binodal via bilayer interdiffusion experiment with the help of ToF-SIMS, such as P3HT:PC 61 BM, 18,22 PCDTBT:PC 71 BM, 19 P3HT:EH-IDTBR, 5 etc.…”