  The ability to tune the gaps of direct bandgap materials has tremendous
potential for applications in the fields of LEDs and solar cells. However, lack
of reproducibility of bandgaps due to quantum confinement observed in
experiments on reduced dimensional materials, severely affects tunability of
their bandgaps. In this letter, we report broad theoretical investigations of
direct bandgap one-dimensional functionalized isomeric system using their
periodic potential profile, where bandgap tunability is demonstrated simply by
modifying the potential profile by changing the position of the functional
group in a periodic supercell. It is verified for known synthetic, as well as
natural polymers (biological and organic), and also for other one-dimensional
direct bandgap systems. This insight would greatly help experimentalists in
designing new isomeric systems of various bandgap values for polymers and
one-dimensional inorganic systems for LEDs applications, and for effectively
harvesting energy in solar cells.
