  We study the thermoelectric performance of $90^0$-bent graphene nanoribbons
containing nanopores for optimized design of multiple functional circuits
including thermoelectric generators. We show that the thermal conductance of
the $90^0$-bent ribbons is lower from few times to an order of magnitude
compared to that of armchair and zigzag straight ribbons. Consequently, the
thermoelectric performance of the bent ribbons is better than its straight
ribbon counterparts, in particular at high temperature above 500 K. More
importantly, the introduction of nanopores in the vertical part of the bent
ribbons is demonstrated to strongly enhance their thermoelectric capacity. At
500 K, the figure of merit ZT increases by more than 160% (from 0.39 without
pores to 0.64) with 3 nanopores incorporated, and by more than 200% (up to
0.88) when 24 nanopores are introduced. ZT ~ 1 can be achieved at a temperature
of about 1000 K. In addition, the thermoelectric performance is shown to be
further improved by combining asymmetrical leads. This study demonstrates that
$90^0$-bent ribbons with nanopores have decent thermoelectric performance for a
wide range of temperatures and can be used as thermoelectric components in
designs of circuits.
