High-Performance Paper-Based Thermoelectric Generator from Cu₂SnS₃ Nanocubes and Bulk-Traced Bismuth

Flexible paper-based thermoelectric generators (PTEGs) have drawn significant interest in recent years due to their various advantages such as flexibility, adaptability, environment friendliness, low cost, and easy fabrication process. However, the reported PTEG's output performance still lags behind the performance of other flexible devices as it is not so easy to obtain a compact film on a paper-based substrate with desirable power output with the standard thermoelectric (TE) materials that have been previously utilized. In this direction, Cu2SnS3 (CTS), an earth-abundant, ternary sulfide, can be a good choice p-type semiconductor, when paired with a suitable n-type TE material. In this article, CTS nanocubes are synthesized via a simple hot injection method and a thick film device on emery paper was prepared and optimized. Furthermore, a flexible, 20-pair PTEG is fabricated with p-type CTS legs and traced and pressed n-type bismuth legs assembled using Kapton tape that produced a significantly high output power of 2.18 mu W (output power density similar to 0.85 nW cm(-2) K-1) for a temperature gradient of Delta T = 80 K. The TE properties are also supported by finite element simulation. The bending test conducted for the PTEG suggests device stability for up to 800 cycles with <0.05% change in the internal resistance. A proof-of-concept field-based demonstration for energy harvesting from waste heat of a motorbike exhaust is shown recovering an output power of similar to 42 nW for Delta T = 20 K, corroborating the experimental and theoretical results.