**5.2 Light emitting diodes**

Metal halide perovskite has great potential due to its easy preparation, low cost and high-performance light emitting diodes. Perovskites in LED applications show well a high colour purity, usually 15–25 nm full width half-colour purity for electroluminescence spectra. The point is here that the colour adjustment can cover the entire visible part of the spectrum by changing the content of different halides within the compounds. Therefore, many researchers have achieved high performance in perovskite quantum dot LED because of their quantum dots, strong luminescence, and high external quantum yields (**Figure 13a**) [25]. The stability problem of organic-inorganic hybrid perovskite can be eliminated by synthesizing the inorganic perovskites (ie CsPbX3) as quantum dots for LED applications (**Figure 13b**) [89]. The performance of perovskite nanoplatelets in LED applications was lower than the quantum dots (**Figure 13c**). As a result, perovskite has a great potential for lighting and display applications as a new generation LED material.

### **5.3 Alternative applications**

FETs, photodetectors, and single photon emitters are the other potential optoelectronic application devices. Liu et al. [90] used perovskite nanoplatelets to produce a FET on a Si/SiO2. For this device, the current-voltage curve showed ohmic contact between the perovskite nanoplatelets and electrodes, and a linear dependency was noted. In that study, they revealed a strong light-material interaction and broadband light harvesting capability of perovskite. Many photodetectors were fabricated based on a horizontal CH3NH3PbI3 nanowire array [49]. The

#### **Figure 12.**

*(a) Photoluminescence spectra of CsPb (X = Cl, Br, I)3 nanoplatelets and (b) wavelength adjustment of perovskite lasing by controlling the content of halide in CsPbX3 perovskite [6, 7, 57]. There is really an extraordinary point about nanowires is that they have very little carrier capture area and the laser quantum efficiency reaches to 100% (reproduced with permission of Ref. [6]).*

**61**

**6. Conclusion**

**Figure 13.**

*In LED applications are generally used a low dimensional perovskite. (a) CH3NH3PbX3 quantum dots are applied to fabricate LED, (b) CsPbX3 quantum dots are used to form LED, (c) CH3NH3PbX3 nanoplatelets* 

response time compared to the obtained photodetectors bulk perovskite and other inorganic nanowire photodetectors is higher in terms of response time of 0.3 ms, 1.3 A W−1 response and a detectivity of 2.5 × 1012 Jones. Park et al. show a remarkable perovskite nanomaterials application that Quantum dots were used as a single photon emitter at standard conditions. CsPbX3 perovskite was used as the leading material to synthesize cubic shapes and quantum dots with an average size of 10 nm. Perovskite quantum dots displayed an excellent photon beam of emitted light and photoluminescence (PL) intensity fluctuations associated with PL life. It is defined that phenomenon as "A-type flashing" that is popular in the quantum dot system.

In this chapter, preparation methods and applications of 2D perovskite nanoparticles were reviewed. The most crucial points for synthesis method are uniformity

*are performed to obtain LED (reproduced with permission of Refs. [25, 89, 91]).*

*Perovskite Nanoparticles*

*DOI: http://dx.doi.org/10.5772/intechopen.94588*

*Perovskite and Piezoelectric Materials*

ing carrier density as low as 1.5 × 1016 cm−3.

**5.2 Light emitting diodes**

**5.3 Alternative applications**

that amplified spontaneous emission can be obtained from perovskite material, research has focused on this subject. Especially, laser obtaining studies were carried out by using perovskite crystal. It has also been shown that perovskite nanowires in high crystalline feature can have a Fabry-Perot gap to obtain a laser in the material [88]. By manipulating the content of the halide in the composition of the perovskite lead to control the emission wavelength and obtain the laser in the entire visible spectrum (**Figure 12a** and **b**) [57]. Zhu et al. showed that laser exposure in CH3NH3 PbX3 with an exponentially low current threshold (220 nJ cm−2) and a correspond-

Metal halide perovskite has great potential due to its easy preparation, low cost and high-performance light emitting diodes. Perovskites in LED applications show well a high colour purity, usually 15–25 nm full width half-colour purity for electroluminescence spectra. The point is here that the colour adjustment can cover the entire visible part of the spectrum by changing the content of different halides within the compounds. Therefore, many researchers have achieved high performance in perovskite quantum dot LED because of their quantum dots, strong luminescence, and high external quantum yields (**Figure 13a**) [25]. The stability problem of organic-inorganic hybrid perovskite can be eliminated by synthesizing the inorganic perovskites (ie CsPbX3) as quantum dots for LED applications (**Figure 13b**) [89]. The performance of perovskite nanoplatelets in LED applications was lower than the quantum dots (**Figure 13c**). As a result, perovskite has a great potential for lighting and display applications as a new generation LED material.

FETs, photodetectors, and single photon emitters are the other potential optoelectronic application devices. Liu et al. [90] used perovskite nanoplatelets to produce a FET on a Si/SiO2. For this device, the current-voltage curve showed ohmic contact between the perovskite nanoplatelets and electrodes, and a linear dependency was noted. In that study, they revealed a strong light-material interaction and broadband light harvesting capability of perovskite. Many photodetectors were fabricated based on a horizontal CH3NH3PbI3 nanowire array [49]. The

*(a) Photoluminescence spectra of CsPb (X = Cl, Br, I)3 nanoplatelets and (b) wavelength adjustment of perovskite lasing by controlling the content of halide in CsPbX3 perovskite [6, 7, 57]. There is really an extraordinary point about nanowires is that they have very little carrier capture area and the laser quantum* 

*efficiency reaches to 100% (reproduced with permission of Ref. [6]).*

**60**

**Figure 12.**

#### **Figure 13.**

*In LED applications are generally used a low dimensional perovskite. (a) CH3NH3PbX3 quantum dots are applied to fabricate LED, (b) CsPbX3 quantum dots are used to form LED, (c) CH3NH3PbX3 nanoplatelets are performed to obtain LED (reproduced with permission of Refs. [25, 89, 91]).*

response time compared to the obtained photodetectors bulk perovskite and other inorganic nanowire photodetectors is higher in terms of response time of 0.3 ms, 1.3 A W−1 response and a detectivity of 2.5 × 1012 Jones. Park et al. show a remarkable perovskite nanomaterials application that Quantum dots were used as a single photon emitter at standard conditions. CsPbX3 perovskite was used as the leading material to synthesize cubic shapes and quantum dots with an average size of 10 nm. Perovskite quantum dots displayed an excellent photon beam of emitted light and photoluminescence (PL) intensity fluctuations associated with PL life. It is defined that phenomenon as "A-type flashing" that is popular in the quantum dot system.

### **6. Conclusion**

In this chapter, preparation methods and applications of 2D perovskite nanoparticles were reviewed. The most crucial points for synthesis method are uniformity

### *Perovskite and Piezoelectric Materials*

and form factor of synthesised nanoparticles. Furthermore, structural, optic, and electrochemical properties of 2D perovskites have been introduced in detail. Due to the low ionic interaction in the crystal structures, organo-halide perovskites exhibit low stability under ambient conditions. However, 2D perovskite nanoparticles still offer a great potential due to the structure-dependent optic and electronic properties.
