Embedding PbS Quantum Dots (QDs) in Pb-Halide Perovskite Matrices: QD Surface Chemistry and Antisolvent Effects on QD Dispersion and Confinement Properties

Abstract

Hybrid materials of metal chalcogenide colloidal quantum dots (QDs) embedded in metal halide perovskites (MHPs) have led to composites with synergistic properties. Here, we investigate how QD size, surface chemistry, and MHP film formation methods affect the resulting optoelectronic properties of QD/MHP "dot-in-matrix" systems. We monitor the QD absorption and photoluminescence throughout synthesis, ligand exchange and transfer into the MHP ink, and characterize the final QD/MHP films via electron microscopy, and transient absorption. Additionally, we are the first to globally map how PbS QDs are distributed on the micron scale within these dot-in matrix systems using 3D tomography time-offlight secondary ion mass spectrometry. The surface chemistry imparted during synthesis directly affects the optical properties of the dot-in-matrix composites. Pb-halide passivation leads to QD/MHP dot-inmatrix samples with optical properties that are well-described by a theoretical model based on a Type-I finite barrier heterostructure between the PbS QD and the MHP matrix. Samples without Pb-halide passivation show complicated size-dependent behavior, indicating a transition from a Type-I heterostructure between the PbS QD wells and MHP barriers for small sized QDs to PbS QDs that are electronically decoupled from the MHP matrix for larger QDs. Furthermore, the choice in perovskite antisolvent crystallization method leads to a difference in the spatial QD distribution within the perovskite matrix, differences in carrier lifetime, and photoluminescence shifts of up to 180 meV for PbS in methylammonium lead iodide. This work establishes an understanding of such emerging synergistic systems relevant for technologies such as photovoltaics, IR-emitters and detectors, and other unexplored technological applications.

Boosting Long-Term Stability of Pure Formamidinium Perovskite Solar Cells by Ambient Air Additive Assisted Fabrication

“…Another additive with several advantages is embedded PbS quantum dots (QDs) into the perovskite thin films. 46 − 49 The chemi-structural match of PbS QDs 28 or nanoplatelets (NPLs) 50 with perovskite (MAPI or FAPI) crystal phase results in the generation of seed-like nucleation regions for the bulky-epitaxial growth of high-quality perovskite absorber with enhanced optoelectronic properties and improved long-term stability. 28 , 50 − 53 Although the huge interest of FAPI PSCs advancement in the stabilization of the FAPI solar cells, and the pieces of evidence that NMP improves its stability, the foundation of the improvement of the formamidinium stabilization was not yet analyzed, 23 , 26 especially beyond low RH in real ambient conditions including medium-high RH fabrication conditions and how these conditions could affect the final device stability.…”

“…The intermediate FAI·PbI 2 ·NMP adduct , assists the formation of smooth and pinhole-free perovskite thin films at ambient atmosphere, and the pure FAPI reaches a stabilized PCE of 16.69% stable for about 1 month at low RH < 20%. Another additive with several advantages is embedded PbS quantum dots (QDs) into the perovskite thin films. − The chemi-structural match of PbS QDs or nanoplatelets (NPLs) with perovskite (MAPI or FAPI) crystal phase results in the generation of seed-like nucleation regions for the bulky-epitaxial growth of high-quality perovskite absorber with enhanced optoelectronic properties and improved long-term stability. ,− Although the huge interest of FAPI PSCs advancement in the stabilization of the FAPI solar cells, and the pieces of evidence that NMP improves its stability, the foundation of the improvement of the formamidinium stabilization was not yet analyzed, , especially beyond low RH in real ambient conditions including medium-high RH fabrication conditions and how these conditions could affect the final device stability. Second, the perovskite-based devices fabricated in air are not always compared with the one fabricated under nitrogen, and the stability tests were still carried out with storage under nitrogen or RH < 20%, , so the investigation of the stability of devices fabricated in both conditions is highly demanding, to shine a light on the origin of the enhanced stabilization under ambient conditions of materials normally affected by humid conditions, , in order to develop industrially friendly fabrication processes.…”

One-Pot Synthesis and Structural Evolution of Colloidal Cesium Lead Halide–Lead Sulfide Heterostructure Nanocrystals for Optoelectronic Applications

“…A recent study demonstrated the introduction of PbS into the perovskite can be possible due to similar lattice constant and related crystal structures. For instance, the crystal structures of MAPbI 3 and PbS are tetragonal and rock-salt, respectively, with Pb being hexacoordinated in each crystal. , Moreover, a shell of PbS onto the perovskite improves black phase stability of iodide-based perovskite and reduces ionic migration in the mixed perovskite system. , These particles show extended optical response and modulation of the electronic properties from n-type to ambipolar transport, with implications for photodetector, photovoltaic, and NIR LED applications. − Sargent et al and other researchers reported another study by embedding the PbS NCs into the bulk matrix of perovskite (hybrid and all-inorganic) for improved optoelectronic properties and the phase stability of iodide based perovskite. ,− The size and composition of the CsPbX 3 NCs and its relative alignment to the band structure of PbS could form two types of energy band alignment, named type I and type II. Type I promotes energy transfer to PbS, and type II promotes carrier separation across the interface.…”

Colloidal quantum dots and metal halide perovskite hybridization for solar cell stability and performance enhancement

“…Some other promising chalcogenide QDs and emerging 2D QDs are also introduced. 79 with permission from the American Chemical Society.…”

“…4e. 79 PbS acted as effective seeding sites to promote the growth of perovskite crystals, delivering substantial morphological improvements in terms of grain size, surface coverage, and uniformity. Through analyses of time-resolved crystal formation kinetics obtained from synchrotron X-rays with a fast subsecond probing time resolution, an important "catalytic" role of the seed-like PbS NCs is clearly elucidated.…”