Colloidal Quantum-Dot Photodetectors Exploiting Multiexciton Generation

TLDR

In photovoltaic devices, excess photon energy above the bandgap is typically lost through Auger decay, limiting efficiency. The authors propose a photoconductive design that harnesses Auger decay to enhance ultraviolet detection sensitivity. Their lead sulfide quantum‑dot thin‑film detector shows up to a four‑fold increase in response when the incident light frequency exceeds several multiples of the bandgap.

Abstract

Reaping Gain from Decay In photovoltaic devices, absorbed light excites electrons into a conduction band and thereby initiates electric current flow. Unfortunately, if the energy of the incident photons exceeds the threshold for this excitation (the bandgap), the excess tends to be wasted. Initially, a photon bearing several multiples of the bandgap energy may correspondingly promote several electrons, but before these can begin to travel through a circuit, most of them drop back down to the immobile state, transferring their packet of energy to a lone remaining carrier in a process termed “Auger decay.” Sukhovatkin et al. (p. 1542 ) show that a photoconductive device design can actually leverage the Auger decay process to improve sensitivity in ultraviolet detection. Their detector, a thin film assembled from lead sulfide quantum dots, improves its response by up to a factor of four when the incident light frequency rises to several multiples of the bandgap.