Highly Passivated n-Type Colloidal Quantum Dots for Solution-Processed Thermoelectric Generators with Large Output Voltage

Abstract

Colloidal quantum dots (CQDs) are attractive materials for thermoelectric applications due to their simple and low-cost processing; advantageously, they also offer low thermal conductivity and high Seebeck coefficient. To date, the majority of CQD thermoelectric films reported upon have been p-type, while only a few reports are available on n-type films. High-performing n- and p-type films are essential for thermoelectric generators (TEGs) with large output voltage and power. Here, high-thermoelectric-performance n-type CQD films are reported and showcased in high-performance all-CQD TEGs. By engineering the electronic coupling in the films, a thorough removal of insulating ligands is achieved and this is combined with excellent surface trap passivation. This enables a high thermoelectric power factor of 24 µW m−1 K−2, superior to previously reported n-type lead chalcogenide CQD films operating near room temperature (<1 µW m−1 K−2). As a result, an all-CQD film TEG with a large output voltage of 0.25 V and a power density of 0.63 W m−2 at ∆T = 50 K is demonstrated, which represents an over fourfold enhancement to previously reported p-type only CQD TEGs.