Abstract:Time-resolved terahertz spectroscopy and combination of quantum chemistry modeling and molecular dynamics simulations were used for the determination of charge carrier mobility in poly[methyl(phenyl)silylene]. Using time-resolved THz spectroscopy we established the on-chain charge carrier drift mobility in PMPSi as 0.02 cm(2) V(-1) s(-1). This value is low due to the formation of polarons: the hole is self-trapped in a potential formed by local chain distortion and the transient THz conductivity spectra show s… Show more
“…We therefore conclude that the generation of gauche defect and local chain distortion can reduce the in-plane mobility. Indeed, the mobility reduced by gauche defect and local chain distortion has been theoretically predicted 57 and experimentally observed in organic thin film transistor 26 . Fig.…”
The chemical nature of the organic cations governs the optoelectronic properties of two-dimensional organic-inorganic perovskites. But its mechanism is not fully understood. Here, we apply femtosecond broadband sum frequency generation vibrational spectroscopy to investigate the molecular conformation of spacer organic cations in two-dimensional organic-inorganic perovskite films and establish a correlation among the conformation of the organic cations, the charge carrier mobility, and broadband emission. Our study indicates that both the mobility and broadband emission show strong dependence on the molecular conformational order of organic cations. The gauche defect and local chain distortion of organic cations are the structural origin of the in-plane mobility reduction and broad emission in two-dimensional organic-inorganic perovskites. Both of the interlayer distance and the conformational order of the organic cations affect the out-of-plane mobility. This work provides molecular-level understanding of the conformation of organic cations in optimizing the optoelectronic properties of two-dimensional organic-inorganic perovskites.
“…We therefore conclude that the generation of gauche defect and local chain distortion can reduce the in-plane mobility. Indeed, the mobility reduced by gauche defect and local chain distortion has been theoretically predicted 57 and experimentally observed in organic thin film transistor 26 . Fig.…”
The chemical nature of the organic cations governs the optoelectronic properties of two-dimensional organic-inorganic perovskites. But its mechanism is not fully understood. Here, we apply femtosecond broadband sum frequency generation vibrational spectroscopy to investigate the molecular conformation of spacer organic cations in two-dimensional organic-inorganic perovskite films and establish a correlation among the conformation of the organic cations, the charge carrier mobility, and broadband emission. Our study indicates that both the mobility and broadband emission show strong dependence on the molecular conformational order of organic cations. The gauche defect and local chain distortion of organic cations are the structural origin of the in-plane mobility reduction and broad emission in two-dimensional organic-inorganic perovskites. Both of the interlayer distance and the conformational order of the organic cations affect the out-of-plane mobility. This work provides molecular-level understanding of the conformation of organic cations in optimizing the optoelectronic properties of two-dimensional organic-inorganic perovskites.
“…Our molecular dynamic modelling of PMPSi suggested an average delocalisation length of 19-20 monomer units. 4 The difference is probably caused by the slightly larger side groups in PMPSi, which leads to motion hindering; thus, the polymer chain is less deformed, and the conjugation is extended. The addition of the dynamic electron-phonon term causes the reorganisation energy to rise by ,4%, while the resulting charge carrier mobility is descreased by ,25%.…”
Section: Resultsmentioning
confidence: 99%
“…This is due to the fact that this method does not account for the exchange interaction at long range, which is needed for the correct description of the delocalised hole. 4 For this reason, only the values resulting from CAM-B3LYP calculations will be taken into consideration. Table 2 summarises all the terms needed for the charge carrier mobility evaluation of chain lengths 16 and 20.…”
Section: Resultsmentioning
confidence: 99%
“…On chain charge carrier mobility was measured by microwave photoconductivity 1-3 and pump and probe technique. 4 Both methods yielded the value of the charge mobility 0?02 cm 2 V 21 s 21 . Electron-hole pairs were generated by laser flash.…”
Intrachain charge carrier transport was studied by means of theoretical computing on the model polymer poly[methyl(phenyl)silylene]. The Marcus theory, in which a dynamic electron-phonon coupling term was inserted into the reorganisation energy, was used for the modelling. The on chain charge carrier mobility was determined as 0?06 cm 2 V 21 s 21 for 16 mer. For 20 mer, the lower value was found (i.e. 0?005 cm 2 V 21 s 21 ). The experimental value obtained by microwave photoconductivity and time resolved terahertz spectroscopy (pump and probe method) was reported as 0?02 cm 2 V 21 s 21 .
“…The decrease can be linked to the local chain distortion of organic cations, [18] which is explained by the localization and selftrapping of charge carriers in potential wells caused by this disorder. [262,263]…”
optoelectronic properties akin to industrial juggernauts gallium arsenide and silicon. [1,2] Yet, the materials are compatible with solution-processing techniques such as inkjet printing and spray coating. [3] This unprecedented combination has led to the development of solar cells which already show power conversion efficiencies of over 25%, similar to state-of-the-art poly-Si and other thin-film technologies, in just over 10 years of development. [4] Hybrid perovskites are particularly interesting for indoor applications, with impressive efficiencies of over 35% demonstrated under indoor illumination which may prove a viable option to power the ever expanding Internet of Things. [5] Rather than competing with the current technology giants, perovskites can work together with other solar cell technologies in a tandem configuration. Record efficiencies of over 29% for silicon-perovskite tandem solar cells have already been reported and further progress is expected in the near future. [6] Although perovskite solar cells (PSCs) are on the verge of mass production, two main challenges remain: stability [7] and toxicity. [8] Multiple reviews already address the toxicity concern, and it will not be discussed here. [9][10][11] Layered hybrid perovskites (LPKs) have emerged as an answer to battle stability concerns. Although known for decades, LPKs have only recently been incorporated in photovoltaic (PV) applications, resulting in modest device power conversion efficiencies due to poorer optoelectronic properties. [12][13][14] However, their key advantage is the stabilizing effects of the organic interlayers, which prevents perovskite degradation. [15,16] The organic spacer inhibits ion migration which prevents the formation of irreversible degradation products. [17] Alternatively, LPKs can be deposited over the state-of-the-art perovskite materials to combine the high performance of 3D perovskites with the stabilizing properties of LPKs. [15] Here, the limiting factor is inefficient charge transport across the organic interlayer, currently preventing the full exploitation of the layered structure in PSCs.This can be approached in two ways, either by keeping the LPK layer very thin, currently the most popular approach, or by increasing the electrical conductivity of the material. [18,19] The conductivity can be enhanced through increasing the number of inorganic layers n, but this comes at the price of reduced stability. [20][21][22] The better approach is to enhance the charge transport in LPKs through the molecular engineering of the organic Layered hybrid perovskites (LPKs) have emerged as a viable solution to address perovskite stability concerns and enable their implementation in wide-scale energy harvesting. Yet, although more stable, the performance of devices incorporating LPKs still lags behind that of state-of-the-art, multication perovskite materials. This is typically assigned to their poor charge transport, currently caused by the choice of cations used within the organic layer. On balance, a compromise bet...
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