Enhancement of carrier mobility due to a secondary structural arrangement resulting from the substituents in a porphyrin transistor was observed. OSCFETs based on two different porphyrin derivatives displayed excellent mobilities of 2.57 and 0.48 cm2 V-1 s-1. Both molecules generate similar J-aggregations, but enhanced mobility of one of the derivative is due to the typical secondary structural arrangement caused by the steric effect substituents on the porphyrin ring. Both were synthesized by Sonogashira coupling reaction between 1-ethynyl-4-hexylbenzene and [5,15-dibromo-10,20-di(4-hexylphenyl)porphyrinato]zinc(II) and [5,15-dibromo-10,20-di(2,6-dietoxyphenyl)porphyrinato]zinc(II) However, considerably high packing density of J-aggregated arrays exists in one of the derivative, as confirmed by comparison of the total number of lattice points in the unit cells of single-crystals of both derivatives. Thus strong π–π interactions and secondary structural arrangement could be responsible for improved mobility in less stericaly hindered derivative. Thus alongwith a nice synthesis which is no doubt important, the design and the deep studies like X-ray, AFM, Powder diffractions etc are too a crucial requirement is the key message which this publication is giving to the organic material chemist communities.