A recently published review on Applied Surface Science Advances has summarized the current state of Lead-Free Perovskite Based Heterojunction Photodetectors.
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Hybrid perovskite materials are widely acknowledged to have a significant practical impact on next-generation photonics technology. Because of their distinct and better optoelectronic features, lead-based materials are the most common. However, the high perceived toxicity of Pb, which may slow down or even impede the rate of commercialization, has raised some questions about the presence of Pb in these devices.
In the quest for a trade-off between high performance and nontoxicity, it has become essential to replace lead with a nontoxic element while still achieving a comparable level of performance and reasonably long-term stability.
Advantages of Perovskite Materials
For a variety of device applications, including photonic and optoelectronic, perovskite materials have proven to be the efficient, affordable, and most promising energy materials. The distinctive physical characteristics of perovskite materials, such as their high dielectric constant, ferroelectric characteristics, long-range ambipolar charge transport, low exciton-binding energy, high absorption coefficient, and more, have attracted the attention of many photovoltaic and optoelectronic researchers.
A fundamental class of optoelectronic devices, photodetectors (PDs), convert photons into electric impulses. Several areas of research rely on the performance of PDs to deliver transformational results. For example:
- Photodetectors are crucial for achieving signal-efficient photoelectron conversion in optical communication systems. The range of frequencies that the detector can accommodate directly affects the responsivity.
- To determine a person's health status, perovskite photodetectors can be used in wearable electronic devices that target the skin surface. Fluorescence and biomolecules can provide information about tissue structure to photo-detectors.
- In imaging applications, the superior performance of the PD affects the resolution and information that can be attained.
Perovskite-Based Heterojunction Photodetectors
In order to create high-performance photodetectors, heterojunctions are developed. These heterojunctions provide an electrical field that improves collection efficiency and suppresses the recombination of photogenerated carriers. The performance of the PD's detecting function will have a considerable impact on the efficacy of the aforementioned optoelectronic devices.
Building semiconductor heterojunctions by fusing two distinct semiconducting phases is a common technique for improving the performance of PDs. The heterojunction is an interface between two solid materials. The interface encompasses fast ion conductors, metallic materials, insulators, and semiconductors. It consists of two regions or layers of semiconductors that are not similar to one another.
In contrast to a homo-junction, the band gaps in heterojunction semiconducting materials are different. Many solid-state device applications benefit from tailoring electronic energy bands. A hetero-structure is a component that combines numerous heterojunctions.
The heterojunction photodetectors are highly sensitive to light, compact, lightweight, linear, low resistance, low dark current, low noise, and have high quantum efficiency.
Lead-Free Perovskite Photodetectors
Due to their superior optoelectronic qualities, Pb-based perovskite materials have become widely employed for developing heterojunction photodetectors. But Pb-based perovskites present two significant challenges. On the one hand, the material's instability in the presence of light, heat, and moisture restricts its working environment. Also, the toxic nature of the Pb element in Pb-perovskite has led to restrictions on its use in many countries, severely limiting its potential for use in consumer electronics. Hence, creating a lead-free perovskite-based heterojunction photodetector is crucial from both a theoretical and practical standpoint.
Many lead-free perovskite-based heterojunction photodetectors have been experimented with recently. Some examples are:
- Lead-free single crystal perovskite CsCu2I3 created by anti-solvent evaporation-assisted crystallization. Here, on the surface of a CsCu2I3 single crystal, a nanostructured CuI film was then created via water treatment to create a CsCu2I3/CuI planar heterojunction. The porous CuI surface layer's ability to trap light improves the photodetector's performance dramatically.
- A Tin-based halide perovskite Pb-free nano-composites for high-performance Indium Tin-Oxide/Zinc Oxide/CsSnBr3:P3HT/CuSCN/Ag photodetectors. These PDs display reduced dark current and increased charge carrier density.
- A photodetector with a heterojunction of SnO2/CABB(Cs2AgBiBr6) has been shown to be improved by adding solvent as part of a post-treatment technique. This improved heterojunction photodetector exhibits good photodetection performance.
- A Ga2O3/CuBiI4 heterojunction UV photodetector was designed using Metal-organic chemical vapor deposition and spin-coating techniques. The light-absorbing qualities of the Ga2O3 film and the CuBiI4 film in the absorption spectrum provide outstanding photoelectric capabilities.
- BFO-based self-powered photodetectors have shown improved response speed when adding a thin film of BFO perovskite between the wide-optical band gap p-type and n-type semiconductors.
- In-depth research has been undertaken on the impact of V2O5 interface passivation and thickness on the heterojunction photo response performance of V2O5/n-Si heterojunction photodetectors produced using a thermal evaporation approach. The self-powered, highly stable, quick reactions and efficiency of the V2O5/n-Si photodetectors make them ideal for mass manufacturing. They would also shed light on carrier transportation and aid in the fabrication of other heterojunction devices.
Heterojunctions are unquestionably essential and promising designs for photoelectric conversion. They have broad surfaces, effective photo-carrier collection and conversion, tunable routes, and better light trapping. The fundamental characteristics of Pb-free perovskite materials have to be studied progressively in order to decide which is the best substitute for systems based on Pb-atoms. The substitute materials should also be widely available, inexpensive, stable, and solution processable.
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References and Further Reading
Swayam Aryam Behera, P. Ganga Raju Achary, Lead free perovskite based heterojunction photodetectors: A mini review, Applied Surface Science Advances,
Volume 14,2023, 100393, ISSN 2666-5239, https://doi.org/10.1016/j.apsadv.2023.100393
J. Han, J. Wang Photodetectors based on two-dimensional materials and organic thin-film heterojunctions Chinese Phys. B., 28 (2019), p. 17103 https://iopscience.iop.org/article/10.1088/1674-1056/28/1/017103/meta
W. Tian, H. Sun, L. Chen, P. Wangyang, X. Chen, J. Xiong, L. Li Low-dimensional nanomaterial/Si heterostructure-based photodetectors InfoMat, 1 (2019), pp. 140-163, 10.1002/inf2.12014
D. Hao, J. Zou, J. Huang Recent developments in flexible photodetectors based on metal halide perovskite InfoMat, 2 (2020), pp. 139-169, 10.1002/inf2.12053