posted on 2023-12-12, 18:30authored byDarshan
H. Parmar, Benjamin Rehl, Ozan Atan, Sjoerd Hoogland, Edward H. Sargent
Colloidal quantum dot (CQD) photodetectors (PDs) can
detect wavelengths
longer than the 1100 nm limit of silicon because of their highly tunable
bandgaps. CQD PDs are acutely affected by the ligands that separate
adjacent dots in a CQD-solid. Optimizing the exchange solution ligand
concentration in the processing steps is crucial to achieving high
photodetector performance. However, the complex mix of chemistry and
optoelectronics involved in CQD PDs means that the effects of the
exchange solution ligand concentration on device physics are poorly
understood. Here we report direct correspondence between simulated
and experimental transient photocurrent responses in CQD PDs. For
both deficient and excess conditions, our model demonstrated the experimental
changes to the transient photocurrent aligned with changes in trap
state density. Combining transient photoluminescence, absorption,
and photocurrent with this simulation model, we revealed that different
mechanisms are responsible for the increased trap density induced
by excess and deficient active layer ligand concentrations.