Eco-friendly renewable energy conversion methods are constantly investigated. Thermoelectric devices, directly converting thermal into electrical energy, show high potential for utilizing waste heat into useful electricity. Yet enhancing their efficiency is a challenging task. Below 300 °C, Bi2TexSe3-x thermoelectric alloys are considered to be the most efficient for such applications. In the current research, by controlling the specific compositions and the synthesis route, optimizing the electron doping level and minimizing the lattice thermal conductivity values, very high thermoelectric figure of merit values were obtained beyond ∼170 °C. It is shown that upon combining the currently reported Bi2Te2.4Se0.6 and Bi2Te1.5Se1.5 alloys with previously reported highly efficient p- and n-type Bi2Te3 based compositions, a remarkable thermoelectric efficiency of ∼9.6% can be achieved for a relatively low temperature difference of 250 °C.