Polymer chain/nanocrystal ordering in thin films of regioregular poly(3-hexylthiophene) and blends with a soluble fullerene

Abstract

Here we report a study of the polymer chain/nanocrystal ordering in thin films (nanolayers) of regioregular poly(3-hexylthiophene) (P3HT) and blends of P3HT with a soluble fullerene derivative. A detailed analysis has been made of two dimensional (2D) grazing incidence X-ray diffraction (GIXRD) measurements with synchrotron radiation. P3HT samples with three different levels of regioregularity (RR) were synthesized and used to investigate the influence of RR on the chain ordering in thin films. Blend films were also prepared to investigate the influence of fullerene molecule addition on chain ordering. For the analysis, one dimensional (1D) GIXRD patterns were extracted from the 2D images for varying azimuthal angles, allowing information to be obtained for chain ordering in both the out-of-plane (OOP) and in-plane (IP) directions. These results show that the degree of P3HT chain ordering is strongly affected by RR, and that thermal annealing improves chain ordering in the OOP direction. This observation is in good agreement with high resolution transmission electron microscope measurements of film nanomorphology.

Abrupt Morphology Change upon Thermal Annealing in Poly(3‐Hexylthiophene)/Soluble Fullerene Blend Films for Polymer Solar Cells

“…As shown in Figure 3, the diffraction pattern of P3HT chains did not change monotonically with the annealing time. The intensity (brightness) of diffraction image, which corresponds to (100), (200), and (300) peaks11, 16 of P3HT crystals, was initially increased by annealing up to 5 min but decreased abruptly after 7 min and then began to increase again after 20 min. After this time, no pronounced change was observed from the 2D images.…”

“…Further analysis focusing on the change of diffraction intensity with azimuthal angle ( α ; refer to Fig. 1b) was carried out to understand the P3HT chain alignment between the OOP and the IP directions 16, 21. Representative diffraction profiles with azimuthal angles are given in Figure 8a and b, which display a huge reduction in the (100) intensity as α decreases.…”

“…In particular, the thermal annealing process for either films or devices is essential to secure a high efficiency because the recrystallization of P3HT molecules in the as‐coated blend films is necessary for better light absorption and charge (hole carriers) transport. In this regard, the nanostructure of P3HT:PCBM blend films before and after thermal annealing has been studied in part by employing grazing angle X‐ray diffraction (GIXD) and/or transmission electron microscopy (TEM) 11, 16, 17. However, so far, no study has been carried out for in situ monitoring of nanostructural changes in the P3HT:PCBM blend films with thermal annealing time, although there are a few reports on device performance variation with thermal annealing time 8, 9, 14…”

Systematic analysis of processing parameters on the ordering and performance of working poly(3-hexyl-thiophene):[6,6]-phenyl C61-butyric acid methyl ester solar cells

“…Many studies indicate that the control of this bulk polymer microstructure is mandatory for improved device performance. 6,8,9,[15][16][17] A direct investigation of devices in operation, as opposed to a theoretical or projected performance from films produced on ideal substrates, is warranted to confirm which of the observed structural features are critical in real devices. From this, insights into the device characteristics and the necessity of various manufacturing steps can be established.…”

Organic Photovoltaic Cells Based On Solvent‐Annealed, Textured Titanyl Phthalocyanine/C60 Heterojunctions

“…[14][15][16][17] Blended heterojunction OPVs based on semiconducting polymers and small molecule or nanoparticle acceptor phases are ''textured'' at smaller length scales, after spin-casting and annealing, and produce high efficiency OPVs. [3,13,[18][19][20][21]48,49] If vectoral charge transport pathways were sustained after the annealing step, the efficiencies of these blended heterojunction OPVs might be even higher. The solvent annealing approach shown here is easy to implement, and using either tetravalent or trivalent metal Pcs, can simultaneously texture the film and extend their photoactivity well into the near-IR.…”