Nanocrystal‐Enabled Perovskite Heterojunctions in Photovoltaic Applications and Beyond

Abstract

Heterojunctions are used to tailor the properties of semiconductors in optoelectronic devices, yet for emerging devices composed of metal halide perovskites, fabricating perovskite/perovskite heterojunctions has proved challenging due to solvent incompatibilities and rapid homogenization due to ion migration. Recent studies have demonstrated various strategies for using perovskite nanocrystals as a component to fabricate perovskite/perovskite heterojunctions, either with a perovskite thin film or a second nanocrystal layer. Heterojunctions such as these can impart many advantages of both bulk and nanocrystalline perovskite morphologies. This perspective focuses on recent developments of solution‐processed perovskite heterojunctions for solar cells and novel optoelectronic devices, in particular, highlighting the demonstrated and potential advantages of nanocrystal‐enabled fabrication strategies. A central tenet of this perspective is that the synthesis and dispersion of perovskite nanocrystals in non‐polar organic solvents offers a key processing advantage over traditional perovskite precursor solutions in polar solvents since the former allows for layer‐by‐layer deposition without dissolving an underlying perovskite film or crystal. This processing advantage, coupled with nanocrystal size control and ligand chemistry, enables perovskite heterojunctions with highly tunable optical and electrical properties. Such heterojunctions may enable disruptive technological advances in broad classes of devices such as solar cells, photodetectors, sensors, and (in)coherent photon sources with tunable polarization.

Synthesis and Properties of Halide Perovskites Nanocrystals Toward Solar Cells Application

“…Along with lower interfacial recombination losses and defect passivation, heterojunctions between PNCs and MHPs also improve the charge extraction efficiency and contribute to the high-performance MHP solar cells. [153] The HP NCs such as Mn-doped CsPbCl 3 NCs as interfacial layer is known to promote energy down-conversion process by significantly reducing the parasitic absorption by substrates (e.g., glass), and thus, in turn, improve the overall PCE of the devices. [154,155] In addition to this, self-assembled NCs layer on top of the HP bulk thin film can act as the localized "gratings" by recycling back the usually lost unabsorbed photons through "fluorescence resonance energy transfer" (FRET) process to the bulk absorber.…”

Ion Diffusion Dynamics and Halogen Mixing at the Heterojunction of Halide Perovskites: Atomistic Insights

“…54 In contrast, for developing stable heterostructures in novel all-perovskite architecture, the interfacial anion migration must be mitigated. 55,56 The clean heterojunctions preserve the band alignment and consequently facilitate photocarrier transport between semiconductors. 4,57,58 These heterostructures are key components for all-perovskite tandem solar cell devices.…”

“…In contrast, for developing stable heterostructures in novel all-perovskite architecture, the interfacial anion migration must be mitigated. , The clean heterojunctions preserve the band alignment and consequently facilitate photocarrier transport between semiconductors. ,, These heterostructures are key components for all-perovskite tandem solar cell devices. − Hautzinger et al successfully introduced graphene as the ion-blocking layer between the CsPbBr 3 /CsPbI 3 heterostructure for sustaining an atomically sharp interface . Chin et al studied halide mixing at perovskite bilayers and found that CsPbBr 3 /Cs 4 PbCl 6 heterojunctions showed limited anion intermixing, showing a way to suppress ion mixing at the perovskite heterojunction using zero-dimensional/three-dimensional/0D (0D/3D/0D) structures .…”

In Situ PL Tracking of Halide Exchange at 3D/QD Heterojunction Perovskite Solar Cells

“…Due to the ionic character of metal halide perovskites (MHPs), there is notable high mobility of halide ions, making QDs prone to undergoing halide ion exchange reversible reactions. , Despite being reported as a promising and fast method to obtain QDs , or bulk films − of different compositions, or even to real-time monitoring of chemical reactions, these exchange reactions are pointed out as one of the challenges to obtaining stable perovskite/perovskite heterojunctions. , The halide exchange reaction has been studied between QDs of different compositions and at the bulk/bulk solid interface, but its behavior at the nano/bulk interface (i.e., QD/3D) remains unexplored. In this study, for the first time, we conduct a comprehensive in situ investigation of the interfacial halide dynamics between QDs and bulk (3D) perovskite films through photoluminescence ( in situ PL) measurements.…”