3.3. X-ray diffraction analysis
The XRD pattern of P3HT-96, P3HT-70 and P3HT-58 is shown in Fig. 2.
The P3HT-96 shows strong first peak at 2 = 5.4◦ and two weak peaks at 2 = 11◦ and 16◦ and are consistent with the reported values [20,21]. The absence of peaks at 2 = 11◦ and 16◦ for P3HT-70 and P3HT-58 indicates that the polymers are amorphous in nature. This is because; regioregular P3HT undergo macromolecular self assembly due to their regular arrangement of side chain resulting well ordered lamellar structures [20]. On the other hand due to head to head and tail to tail coupling of regioirregular P3HTs, the main chains do not form ordered structure and hence these polymers mostly have amorphous structure [4]. This is also supported by the literature that even P3HT with 80% regioregularity is amorphous in nature [22].