  The waste heat management becomes very important with increasing energy
demand and limited fossil resources. Here, we demonstrate thermoelectric
performance of allotropic TeSe2. Based on the first-principle calculations, we
confirm the energetic and kinetic stability of five TeSe2 allotropes. We
predict {\delta}-TeSe2 as a new direct band gap semiconductor having 1.60 eV
direct band gap. All the TeSe2 allotropes exhibit band gap in UV-Vis region.
The structural phases are clearly distinguished using simulated scanning tunnel
microscopy. The room temperature Seebeck coefficient is maximum of 4 V/K for
{\delta}-TeSe2. We show that room temperature thermoelectric figure of merit
(ZT) can reach up to 3.1 with p-type doping in {\delta}-TeSe2. Moreover,
temperature and chemical potential tuning extends the thermoelectric
performance of TeSe2 allotropes. We strongly believe that our study is
compelling from an experimental perspective and holds a key towards fabrication
of thermoelectric devices based on TeSe2.
