Fast-Grown Interpenetrating Network in Poly(3-hexylthiophene): Methanofullerenes Solar Cells Processed with Additive

Abstract

With the aim of revealing the role of additives in polymer solar cells, different amounts of 1,8-octanedithiol (OT) were added to the poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend system in order to observe the transition between systems with and without additive. We found that highly efficient P3HT:PCBM networks can be formed in the very early stage of the spin-coating process when a small amount of additive was added. The carrier mobilities of this fast-grown network were found to be comparable with those processed with solvent annealing. As a result, short circuit current density (J sc) as high as ∼9 mA cm−2 can be obtained and the fill factor (FF) can reach ∼62%. The power conversion efficiency (PCE), however, is limited by the low open circuit voltage (V oc) of the devices processed with OT. According to the grazing incidence X-ray diffraction data, a much shorter interlayer spacing (d (100) ∼ 15.6−15.7 Å) compared with those processed with different methods is observed in the polymer blends processed with OT, which is likely the reason for the low V oc.

On the morphology of polymer‐based photovoltaics

“…10(a-d)]. 67 They found that with small amounts of OT added to the casting solvent, dichlorobenzene, the device performance was markedly enhanced with a strong increase in J sc and FF being found along with a slight decrease in the open circuit voltage, V oc . The presence of OT induced the crystallization of P3HT, which could be seen from the color of the film and the absorption profile.…”

Relation Between Nanomorphology and Performance of Polymer-Based Solar Cells

“…While PCBM is known to quench the PL of P3HT effectively in the well mixed blends. (Chen, Yang, Yang, Sista, Zadoyan, Li & Yang, 2009) The photoluminescence was shown to increase with increasing amount of 1,8-octanedithiol (Fig. 16 (b)), suggesting that the phase separation between the P3HT and PCBM is increasing since the exciton diffusion distance is on the same order of magnitude.…”

“…The effect of additive concentration in the solution was clearly observed in surface topography images in AFM. (Chen, Yang, Yang, Sista, Zadoyan, Li & Yang, 2009) AFM provides information about the film surface only, the bulk of the film has been studied using synchrotron-based grazing incidence X-ray diffraction (GIXD) in P3HT:PCBM blends. (Chen, Yang, Yang, Sista, Zadoyan, Li & Yang, 2009) Fig.…”

“…(Chen, Yang, Yang, Sista, Zadoyan, Li & Yang, 2009) AFM provides information about the film surface only, the bulk of the film has been studied using synchrotron-based grazing incidence X-ray diffraction (GIXD) in P3HT:PCBM blends. (Chen, Yang, Yang, Sista, Zadoyan, Li & Yang, 2009) Fig. 13 (a) patterns of the as-spun P3HT:PCBM films with different concentrations of 1,8-octanedithiol.…”

“…16 (b)), suggesting that the phase separation between the P3HT and PCBM is increasing since the exciton diffusion distance is on the same order of magnitude. (Xu & Holdcroft, 1993;Zhokhavets et al, 2006) (Chen, Yang, Yang, Sista, Zadoyan, Li & Yang, 2009 (Pivrikas et al, 2008). Copyright 2008, with permission from Elsevier.…”