Substrate and Excitation Intensity Dependence of Saturable Absorption in Perovskite Quantum Dot Films

Abstract

Saturable absorption in perovskite quantum dot (PQD) films, leading to saturation in photoluminescence (PL), is reported. PL of drop-casting films was used to probe how excitation intensity and host–substrate influence the growth of PL intensity. The PQD films were deposited on single-crystal GaAs, InP, Si wafers and glass. Saturable absorption was confirmed through PL saturation in all films, with different excitation intensity thresholds, suggesting strong substrate-dependent optical properties, resulting from absorption nonlinearities in the system. The observations extend our former studies (Appl. Phys. Lett., 2021, 119, 19, 192103), wherein we pointed out that the PL saturation in QDs can be used to create all-optical switches in combination with a bulk semiconductor host.

Photoluminescence from Two-Phase Nanocomposites Embedded in Polymers

“…These results are different from a previously reported study on QD absorption or PL detailed balance, where one type of QD solution was drop-cast on different substrates [ 2 ]. In that study, all samples showed saturation in PL, well before the maximum laser power presented in the current work [ 2 ]. However, the underlying mechanism could still have some similarities between the study in [ 2 ] and the current work.…”

“…This extra energy can excite the red dots more and thus can cause their saturation. Also, the red dots do not have any active layer beneath them working as potential absorbers; hence, they saturate like the usual QD films studied in [ 2 , 18 , 19 , 20 ].…”

“…The interdisciplinary nature of nanotechnology allows for the manipulation and design of materials at the atomic and molecular levels, opening new possibilities in fields such as information technology, environmental science, medicine, food safety, agriculture, and more [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. Semiconductor QDs, being a pivotal class of materials, hold significant promise for various nanoscale applications owing to their unique structural, optical, and electrical properties [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. The distinct characteristics of semiconductors make them particularly exciting for researchers and engineers working on nanoscale technologies.…”

“…Although this process is generally consistent, details of how the electronic state changes and the recombination processes could reflect complex events. The changes could occur due to many factors, including but not limited to, scattering and defect or impurity states, interaction between the fluorescing components, environments where the QDs are dissolved/embedded, and interfaces to which they are exposed [ 1 , 2 , 3 , 6 , 7 , 8 , 17 , 18 ]. The mechanism of detailed balance also plays a role in some cases, as has been noted previously [ 2 ].…”

“…Until recently, the influence of QD systems on host materials had not been thoroughly investigated. Earlier reports indicated that the presence of PbS QDs, hetero paired with an undoped GaAs substrate, altered the PL properties of the latter [ 2 , 19 ]. With the rapidly advancing synthesis of composite materials, it becomes crucial to study the interactions and mechanisms altering the optical properties of one or both hetero-paired components.…”