Quantifying the Impact of Grain Boundaries
Grain boundaries act as bottlenecks to charge transport in organic field effect transistors comprising polycrystalline active areas. In the Loo Lab, we have found that the impact of these boundaries depends on the structure of the organic semiconductor (molecular or polymeric) and the method of thin-film formation (solution-processing or thermal evaporation). We have used thin films of triethylsilylethynyl anthradithiophene (TES ADT), a solution-processed molecular semiconductor, to study the impact of TES ADT’s unique interspherulite boundaries (ISBs). Although TES ADT is molecular, we found that TES ADT’s ISBs are similar to polymeric crystallite boundaries. Since in both cases, trapped material bridging the boundaries maintains an electrical pathway between the crystalline regions, these boundaries are less resistive than their thermally-evaporated counterparts, which encompass submicrometer crevices.