Abstract:Perovskite based photovoltaic devices are popularised by the rapid increase in their efficiencies. Understanding the fundamental physics and chemistry processes occurring upon excitation is key. We monitored the temporal evolution of the population and depopulation dynamics of various electronic states in FA MA PbI Br by means of ultrafast transient absorption spectroscopy in the visible and near infrared spectral regions in order to build a fully consistent charge dynamics model of the initial photoprocesses.… Show more
“…Schematic description of band structure of TCMHP is proposed based on the previous reports50,51 and this simplified band diagram consists of one VBM and one CBM in TCMHP as a function of k vector. Major optical transition at R point (VBM → CBM) corresponds to the bandgap (1.59 eV) of TCMHP and the shape of VBM (blue color) and CBM (bark red color) curvatures are rough leading other possible optical transitions.…”
Section: Resultsmentioning
confidence: 49%
“…To address the NLO responses shown in Figure 4a,b, we discussed the NLO phenomena based on the proposed schematic energy band diagram of TCHMP in Figure by following the previous reports,50,51 where one lowest energy conduction band (CBM) and one highest energy valance band (VBM) exist as a function of k . It is worth noting that VBM → CBM is a major optical transition at R point corresponding to the bandgap (1.59 eV) of TCMHP.…”
exceptional properties including high photostability, extremely long charge diffusion length, and thermal stability. The perovskites have become emerging high-performance materials for various optoelectronic applications such as solar cells, [1][2][3] light emitting diodes, [4,5] photodetectors, [6,7] and lasers. [8,9] The halide perovskites also exhibit strong nonlinear optical (NLO) responses, thus opening up possibilities for optoelectronic device applications. [10][11][12][13][14] For instance, organic-inorganic hybrid perovskites with large two-and three-photon absorption (2PA, 3PA) properties [14][15][16] can be utilized in applications such as bioimaging, [17,18] optical limiting, [19] optical sensor protection, [20] and optical data storage. [21] Nonlinear absorption properties of single crystal, nanocrystal, and filmed perovskites have been intensively studied. [10][11][12][13][14][15][16][22][23][24] Recently, lead halide perovskites such as MAPbI 3 (MA = CH 3 NH 3 ) and MAPbBr 3 have shown higher multiphoton absorption (MPA) probability as the excitation wavelength increases in the IR region. [10][11][12][13][14][22][23][24] Johnson et al. [25] reported that the observation of third-order nonlinearities and decay kinetics in MAPbBr 3 and MAPbBr 2 I with different halogen composition. They showed that the third-order nonlinearities of these materials are larger than those of conventional semiconductors. The photoluminescence of MAPbBr 3 single crystal has also been observed in the green region (522-550 nm) with 1044 nm femtosecond laser excitation due to 2PA. [26] Similar nonlinear optical properties were reported in inorganic perovskites, including CsPbI 3 and CsPbBr 3 . [22,27,28] Another type of perovskite, formamidinium lead iodide (FAPbI 3 ), has a low bandgap (1.47 eV) and greater photostability and thermal stability [29,30] than MAPbI 3 . However, FAPbI 3 has a weak structural stability due to humidity, which prevents it from real-life applications. [31] Recently, it has been demonstrated that the mixture of Cs and MAPbI 3 , CsMAPbI 3 , can lead to a stable solar cell with power conversion efficiency of ≈8%. [32] In addition, the mixture of Cs in FAPbI 3 , such as FA 0.9 Cs 0.1 PbI 3 , showed an improved thermal stability and results in high power conversion efficiency of ≈16.5%. [33] By using this material, Yi et al. have demonstrated power conversion efficiency up to 18% with a halide mixer I/Br. [34] The malleable association The versatility of perovskites through chemical composition modification is critical for enhancing performance of a range of potential applications such as light emitters and integrated photovoltaics. However, a systematic study on the nonlinear optical (NLO) responses of these perovskites is still lacking. Here, for the first time, the NLO properties of triple cation mixed halide perovskite (TCMHP) films, (Cs 0.06 FA 0.79 MA 0.15 )Pb (I 0.85 Br 0.15 ) 3 , using Z-scan and time-resolved spectroscopy, are investigated. It is found that TCMHP film shows strong saturable abs...
“…Schematic description of band structure of TCMHP is proposed based on the previous reports50,51 and this simplified band diagram consists of one VBM and one CBM in TCMHP as a function of k vector. Major optical transition at R point (VBM → CBM) corresponds to the bandgap (1.59 eV) of TCMHP and the shape of VBM (blue color) and CBM (bark red color) curvatures are rough leading other possible optical transitions.…”
Section: Resultsmentioning
confidence: 49%
“…To address the NLO responses shown in Figure 4a,b, we discussed the NLO phenomena based on the proposed schematic energy band diagram of TCHMP in Figure by following the previous reports,50,51 where one lowest energy conduction band (CBM) and one highest energy valance band (VBM) exist as a function of k . It is worth noting that VBM → CBM is a major optical transition at R point corresponding to the bandgap (1.59 eV) of TCMHP.…”
exceptional properties including high photostability, extremely long charge diffusion length, and thermal stability. The perovskites have become emerging high-performance materials for various optoelectronic applications such as solar cells, [1][2][3] light emitting diodes, [4,5] photodetectors, [6,7] and lasers. [8,9] The halide perovskites also exhibit strong nonlinear optical (NLO) responses, thus opening up possibilities for optoelectronic device applications. [10][11][12][13][14] For instance, organic-inorganic hybrid perovskites with large two-and three-photon absorption (2PA, 3PA) properties [14][15][16] can be utilized in applications such as bioimaging, [17,18] optical limiting, [19] optical sensor protection, [20] and optical data storage. [21] Nonlinear absorption properties of single crystal, nanocrystal, and filmed perovskites have been intensively studied. [10][11][12][13][14][15][16][22][23][24] Recently, lead halide perovskites such as MAPbI 3 (MA = CH 3 NH 3 ) and MAPbBr 3 have shown higher multiphoton absorption (MPA) probability as the excitation wavelength increases in the IR region. [10][11][12][13][14][22][23][24] Johnson et al. [25] reported that the observation of third-order nonlinearities and decay kinetics in MAPbBr 3 and MAPbBr 2 I with different halogen composition. They showed that the third-order nonlinearities of these materials are larger than those of conventional semiconductors. The photoluminescence of MAPbBr 3 single crystal has also been observed in the green region (522-550 nm) with 1044 nm femtosecond laser excitation due to 2PA. [26] Similar nonlinear optical properties were reported in inorganic perovskites, including CsPbI 3 and CsPbBr 3 . [22,27,28] Another type of perovskite, formamidinium lead iodide (FAPbI 3 ), has a low bandgap (1.47 eV) and greater photostability and thermal stability [29,30] than MAPbI 3 . However, FAPbI 3 has a weak structural stability due to humidity, which prevents it from real-life applications. [31] Recently, it has been demonstrated that the mixture of Cs and MAPbI 3 , CsMAPbI 3 , can lead to a stable solar cell with power conversion efficiency of ≈8%. [32] In addition, the mixture of Cs in FAPbI 3 , such as FA 0.9 Cs 0.1 PbI 3 , showed an improved thermal stability and results in high power conversion efficiency of ≈16.5%. [33] By using this material, Yi et al. have demonstrated power conversion efficiency up to 18% with a halide mixer I/Br. [34] The malleable association The versatility of perovskites through chemical composition modification is critical for enhancing performance of a range of potential applications such as light emitters and integrated photovoltaics. However, a systematic study on the nonlinear optical (NLO) responses of these perovskites is still lacking. Here, for the first time, the NLO properties of triple cation mixed halide perovskite (TCMHP) films, (Cs 0.06 FA 0.79 MA 0.15 )Pb (I 0.85 Br 0.15 ) 3 , using Z-scan and time-resolved spectroscopy, are investigated. It is found that TCMHP film shows strong saturable abs...
“…demonstrated the strong saturable absorption peak of 395 nm as well as the reverse saturable absorption peak of 790 nm (two-photo absorption) and 1200 nm (three-photo absorption) in the mixed triple cation halide perovskite ( Syed et al., 2020 ). Strong three-photo absorption near to the band gap reveals optical stabilization, great spatial confinement, and large penetration depth, which is rooted in phonon-assisted anti-Stokes processes( Minda et al., 2018 ). Figure 9 Crystallization dynamics of perovskites The grazing incidence wide-angle X-ray scattering (GIWAXS) patterns for perovskite films with cation cascade doping as (A) FAMACsRb, and (B) FAMACsRbK, respectively.…”
Summary
Hybrid lead halide ABX
3
perovskite solar cells (PSCs) have emerged as a strong competitor to the traditional solar cells with a certified power conversion efficiency beyond 25% and other remarkable features such as light weight, solution processability, and low manufacturing cost. Further development on the efficiency and stability brings forth increasing attention in the component regulation, such as partial or entire substitution of A/B/X sites by alternative elements with similar size. However, the relationships between composition, property, and performance are poorly understood. Here, the instability of PSCs from the photon-, moisture-, thermal-, and mechanical-induced degradation was first summarized and discussed. In addition, the component regulation from the A/X sites is highlighted from the aspects of band level alignment, charge-carrier dynamics, ion migration, crystallization behavior, residual strain, stoichiometry, and dimensionality control. Finally, the perspectives and future outlooks are highlighted to guide the rational design and practical application of PSCs.
“…In recent years, A-site cation engineering of the ABX 3 perovskite structure, with A being e.g., formamidinium (FA), methylammonium (MA), and/or inorganic (e.g., Cs) cation, has been a hot topic for the study of HC dynamics, and many interesting fundamentals have been revealed by ultrafast spectroscopy techniques 47 , 48 , 51 , 55 . Due to defect tolerance, nanostructure, quantum confinement, and excellent charge transport properties, the low-dimensional halide perovksite [e.g., quantum dots (QDs), nanocrystals (NCs), nanowires (NWs), and nanorods (NRs)] have gained much research attention.…”
Section: Hc In Organic–inorganic Halide Perovskitesmentioning
Hot charge carriers (HC) are photoexcited electrons and holes that exist in nonequilibrium high-energy states of photoactive materials. Prolonged cooling time and rapid extraction are the current challenges for the development of future innovative HC-based optoelectronic devices, such as HC solar cells (HCSCs), hot energy transistors (HETs), HC photocatalytic reactors, and lasing devices. Based on a thorough analysis of the basic mechanisms of HC generation, thermalization, and cooling dynamics, this review outlines the various possible strategies to delay the HC cooling as well as to speed up their extraction. Various materials with slow cooling behavior, including perovskites and other semiconductors, are thoroughly presented. In addition, the opportunities for the generation of plasmon-induced HC through surface plasmon resonance and their technological applications in hybrid nanostructures are discussed in detail. By judiciously designing the plasmonic nanostructures, the light coupling into the photoactive layer and its optical absorption can be greatly enhanced as well as the successful conversion of incident photons to HC with tunable energies can also be realized. Finally, the future outlook of HC in optoelectronics is highlighted which will provide great insight to the research community.
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