scholarly journals Low-frequency lattice phonons in halide perovskites explain high defect tolerance toward electron-hole recombination

2020 ◽  
Vol 6 (7) ◽  
pp. eaaw7453 ◽  
Author(s):  
Weibin Chu ◽  
Qijing Zheng ◽  
Oleg V. Prezhdo ◽  
Jin Zhao ◽  
Wissam A. Saidi

Low-cost solution-based synthesis of metal halide perovskites (MHPs) invariably introduces defects in the system, which could form Shockley-Read-Hall (SRH) electron-hole recombination centers detrimental to solar conversion efficiency. Here, we investigate the nonradiative recombination processes due to native point defects in methylammonium lead halide (MAPbI3) perovskites using ab initio nonadiabatic molecular dynamics within surface-hopping framework. Regardless of whether the defects introduce a shallow or deep band state, we find that charge recombination in MAPbI3 is not enhanced, contrary to predictions from SRH theory. We demonstrate that this strong tolerance against defects, and hence the breakdown of SRH, arises because the photogenerated carriers are only coupled with low-frequency phonons and electron and hole states overlap weakly. Both factors appreciably decrease the nonadiabatic coupling. We argue that the soft nature of the inorganic lattice with small bulk modulus is key for defect tolerance, and hence, the findings are general to other MHPs.

2018 ◽  
Vol 11 (3) ◽  
pp. 702-713 ◽  
Author(s):  
Daniele Meggiolaro ◽  
Silvia G. Motti ◽  
Edoardo Mosconi ◽  
Alex J. Barker ◽  
James Ball ◽  
...  

Electron/hole traps related to interstitial iodine defects show the typical features of iodine photo-electrochemistry, inducing MAPbI3 defect tolerance.


2019 ◽  
Vol 6 (10) ◽  
pp. 105021 ◽  
Author(s):  
Deli Shi ◽  
Zhengwei Xiong ◽  
Jun Li ◽  
Bin Qiang Luo ◽  
Lei Ming Fang ◽  
...  

Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 434 ◽  
Author(s):  
Luis I. Granone ◽  
Konstantin Nikitin ◽  
Alexei Emeline ◽  
Ralf Dillert ◽  
Detlef W. Bahnemann

Physicochemical properties of spinel ZnFe2O4 (ZFO) are known to be strongly affected by the distribution of the cations within the oxygen lattice. In this work, the correlation between the degree of inversion, the electronic transitions, the work function, and the photoelectrochemical activity of ZFO was investigated. By room-temperature photoluminescence measurements, three electronic transitions at approximately 625, 547, and 464 nm (1.98, 2.27, and 2.67 eV, respectively) were observed for the samples with different cation distributions. The transitions at 625 and 547 nm were assigned to near-band-edge electron-hole recombination processes involving O2- 2p and Fe3+ 3d levels. The transition at 464 nm, which has a longer lifetime, was assigned to the relaxation of the excited states produced after electron excitations from O2- 2p to Zn2+ 4s levels. Thus, under illumination with wavelengths shorter than 464 nm, electron-hole pairs are produced in ZFO by two apparently independent mechanisms. Furthermore, the charge carriers generated by the O2− 2p to Zn2+ 4s electronic transition at 464 nm were found to have a higher incident photon-to-current efficiency than the ones generated by the O2− 2p to Fe3+ 3d electronic transition. As the degree of inversion of ZFO increases, the probability of a transition involving the Zn2+ 4s levels increases and the probability of a transition involving the Fe3+ 3d levels decreases. This effect contributes to the increase in the photoelectrochemical efficiency observed for the ZFO photoanodes having a larger cation distribution.


2019 ◽  
Author(s):  
Ji-Sang Park ◽  
Joaquín Calbo ◽  
Young-Kwang Jung ◽  
lucy whalley ◽  
Aron Walsh

<div> <div> <div> <p>The behaviour of grain boundaries in polycrystalline halide perovskite solar cells remains poorly understood. Whereas theoretical studies indicate that grain boundaries are not active for electron-hole recombination, there have been observations of higher non-radiative recombination rates involving these extended defects. We find that iodine interstitial defects, which have been established as a recombination center in bulk crystals, tend to segregate at planar defects in CsPbI3. First-principles calculations show that enhanced structural relaxation of the defects at grain boundaries results in increased stability (higher concentration) and deeper trap states (faster recombination). We show how the grain boundary can be partly passivated by halide mixing or extrinsic doping, which replaces or suppresses the formation of trap states close to the grain boundaries.<br></p> </div> </div> </div>


2020 ◽  
Vol 5 (4) ◽  
pp. 683-690 ◽  
Author(s):  
Ran Shi ◽  
Zhaosheng Zhang ◽  
Wei-hai Fang ◽  
Run Long

CsPbBr3 perovskites containing ferroelastic domains inhibit non-radiative charge recombination by facilitating charge separation and decreasing nonadiabatic coupling.


2021 ◽  
Vol 5 (2) ◽  
Author(s):  
O. Amora

Hybrid lead halide perovskites emerged at the beginning of 2010s decade as one of the most promising materials for photovoltaic applications. Easy and low-cost solution-based fabrication processes can be used, obtaining perovskite solar cells (PSCs) with efficiencies above 20%. However, there still are some major issues to overcome, like stabiliddty, and the general understanding of the recombination mechanisms resHybrid lead halide perovskites emerged at the beginning of 2010s decade as one of the most promising materials for photovoltaic applications. Easy and low-cost solution-based fabrication processes can be used, obtaining perovskite solar cells (PSCs) with efficiencies above 20%. However, there still are some major issues to overcome, like stability, and the general understanding of the recombination mechanisms results particularly puzzling. In this chapter, an analysis is provided on most recent research results about the different mechanisms, location and relationships of charge carrier recombination in PSCs. After introducing the theoretical framework, including the main transport equations and relations with luminescence techniques, the radiative and non-radiative natures of recombination are commented and compared in terms of main contributions. Also, the effects of changing the perovskite composition and morphology are surveyed. The location of the recombination processes, whether in the bulk material or towards the interface, are tackled, as well as related features with the current-voltage hysteresis. On the latter, and along the complete chapter, the dual ionic-electronic conductivity of hybrid lead halide perovskites is particularly attended. ults particularly puzzling. In this chapter, an analysis is provided on most recent research results about the different mechanisms, location and relationships of charge carrier recombination in PSCs. After introducing the theoretical framework, including the main transport equations and relations with luminescence techniques, the radiative and non-radiative natures of recombination are commented and compared in terms of main contributions. Also, the effects of changing the perovskite composition and morphology are surveyed. The location of the recombination processes, whether in the bulk material or towards the interface, are tackled, as well as related features with the current-voltage hysteresis. On the latter, and along the complete chapter, the dual ionic-electronic conductivity of hybrid lead halide perovskites is particularly attended. ybrid lead halide perovskites emerged at the beginning of 2010s decade as one of the most promising materials for photovoltaic applications. Easy and low-cost solution-based fabrication processes can be used, obtaining perovskite solar cells (PSCs) with efficiencies above 20%. However, there still are some major issues to overcome, like stability, and the general understanding of the recombination mechanisms results particularly puzzling. In this chapter, an analysis is provided on most recent research results about the different mechanisms, location and relationships of charge carrier recombination in PSCs. After introducing the theoretical framework, including the main transport equations and relations with luminescence techniques, the radiative and non-radiative natures of recombination are commented and compared in terms of main contributions. Also, the effects of changing the perovskite composition and morphology are surveyed. The location of the recombination processes, whether in the bulk material or towards the interface, are tackled, as well as related features with the current-voltage hysteresis. On the latter, and along the complete chapter, the dual ionic-electronic conductivity of hybrid lead halide perovskites is particularly attended.


2019 ◽  
Author(s):  
Ji-Sang Park ◽  
Joaquín Calbo ◽  
Young-Kwang Jung ◽  
lucy whalley ◽  
Aron Walsh

<div> <div> <div> <p>The behaviour of grain boundaries in polycrystalline halide perovskite solar cells remains poorly understood. Whereas theoretical studies indicate that grain boundaries are not active for electron-hole recombination, there have been observations of higher non-radiative recombination rates involving these extended defects. We find that iodine interstitial defects, which have been established as a recombination center in bulk crystals, tend to segregate at planar defects in CsPbI3. First-principles calculations show that enhanced structural relaxation of the defects at grain boundaries results in increased stability (higher concentration) and deeper trap states (faster recombination). We show how the grain boundary can be partly passivated by halide mixing or extrinsic doping, which replaces or suppresses the formation of trap states close to the grain boundaries.<br></p> </div> </div> </div>


2019 ◽  
Vol 248 ◽  
pp. 105-108 ◽  
Author(s):  
N. Ramesh Reddy ◽  
U. Bhargav ◽  
G. Manoranjani ◽  
M. Mamatha Kumari ◽  
K.K. Cheralathan ◽  
...  

2021 ◽  
Vol 282 ◽  
pp. 128822
Author(s):  
N. Ramesh Reddy ◽  
U. Bharagav ◽  
G. Manoranjani ◽  
M. Mamatha Kumari ◽  
K.K. Cheralathan ◽  
...  

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