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Spin currents can be generated by application of a charge current in a heavy metal or topological insulator, allowing the production of spin-orbit torques. Here we investigate the generation of spin currents due to a thermal gradient, rather than an applied charge current. We study bilayers made from thin films of the topological insulator Bi₂Se₃ with CoFeB, apply a thermal gradient using an adjacent heater, and measure voltage signals arising from spin currents via the inverse spin Hall effect. We observe spin-current generation that is almost an order of magnitude more efficient than in previous measurements of thermally-induced spin currents for W and Pt-based samples.