Printed Lateral p–n Junction for Thermoelectric Generation

Printed thermoelectric generators (TEGs) show promising potential for converting waste heat into useful electricity at a low cost but fall short of exhibiting a conversion efficiency anticipated from materials’ properties. The output power of conventionally printed TEGs in the “π-type” geometry suffers due to low thermal voltage and low current because of high thermal and electrical contact resistance, respectively. Herein, a type of printed p–n junction TEGs (PN-TEGs) as a possible remedy is explored. Two printed PN-TEGs with different thicknesses are fabricated using printed p-type Bi$_{0.5}$Sb$_{1.5}$Te$_3$ and n-type Bi$_2$Te$_{2.7}$Se$_{0.3}$ materials. The PN-TEGs show a promising way to minimize the influence of thermal and electrical resistance in printed TEGs. In the experimental and simulation results, the significant impact of PN-TEGs’ dimensions on their power outputs is revealed. Also, a conventional “π-type” printed TEG is fabricated and its performance is studied. The optimized PN-TEG with a single thermocouple yields ≈14 times higher power output density of 5.3 μW cm$^{−2}$ at a ΔT of 25 K compared to “π-type” printed TEGs.