Picosecond trion photocurrent dynamics in FAPbI₃ quantum dot films

Nanocrystal quantum dot (QD) films have been highlighted as unique building blocks of optoelectronic devices due to their unique properties based on electronic interactions among close-packed QDs. Although the creation and annihilation processes of trions play important roles in optical responses of isolated QDs, their contributions to photocurrent conversion processes in QD films are unclear. Here, we studied trion dynamics in QD films by transient photocurrent measurements. We observed that the transient photocurrent signal has two decay components: a fast trion component with a lifetime shorter than 1 ns and a slow exciton component with several tens of nanoseconds. Moreover, we control the signal amplitude of the fast trion decay component by tuning extra charge doping to QDs. These results demonstrate the control of optoelectronic responses of QD films via bias electric voltage and will pave the way for QD-based ultrafast optoelectronics.