Lattice strain causes non-radiative losses in halide perovskites

Jones, Timothy W.; Osherov, Anna; Alsari, Mejd; Sponseller, Melany; Duck, Benjamin C.; Jung, Young-Kwang; Settens, Charles; Niroui, Farnaz; Brenes, Roberto; Stan, Camelia; Li, Yao; Abdi‐Jalebi, Mojtaba; Tamura, Nobumichi; MacDonald, John Emyr; Burghammer, Manfred; Friend, Richard H.; Bulović, Vladimir; Walsh, Aron; Wilson, Gregory J.; Lilliu, Samuele; Stranks, Samuel D.

doi:10.1039/c8ee02751j

Cited by 412 publications

(461 citation statements)

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“…J52:ITCCM‐O‐based device shows a high EQE EL of 2.4 × 10 –4 , corresponding to a quite small E loss,non‐rad of 0.22 eV, which is among the best result in reported OSCs . It should be noted that inorganic solar cells or perovskite solar cells usually have E loss,non‐rad of ~0.18 eV . As shown in Figure d, both the low driving force for charge generation and the low E loss,non‐rad contribute the low E loss and obtained high V OC .…”

Section: Resultsmentioning

confidence: 89%

Efficient Organic Solar Cells with a High Open‐Circuit Voltage of 1.34 V

et al. 2019

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Summary of main observation and conclusion One of the most important challenges that hinders the power conversion efficiencies (PCEs) of organic solar cells (OSCs) is the modest open‐circuit voltages (VOC) due to large energy losses. The large driving force during for charge generation and the non‐radiative recombination are the main causes of energy losses. To maximize the VOC of OSCs, herein, we modulate the end‐groups and design a non‐fullerene acceptor ITCCM‐O, which shows a bandgap of 2.0 eV. By blending a polymer donor named J52, the device demonstrates a PCE of 5.5% with an outstanding VOC of 1.34 V, which is the highest value for single‐junction OSCs over 5% PCEs. The high VOC is benefited from 1) the negligible driving force for charge transfer, and 2) the suppressed non‐radiative recombination loss, as low as 0.22 V.

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Section: Resultsmentioning

confidence: 89%

Efficient Organic Solar Cells with a High Open‐Circuit Voltage of 1.34 V

et al. 2019

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“…On the other hand, Zhao et al first reported that the most perovskite films made by existing fabrication methods are strained due to the mismatched thermal expansion coefficients between perovskite films and substrates, and strain diminishes the long‐term stability of PSCs . Other studies confirmed the impact of strain on the stability of PSCs . The lattice strain in perovskite film has been proposed to impact ion migration, defect formation, and carrier dynamics in PSCs.…”

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confidence: 99%

“…Other studies confirmed the impact of strain on the stability of PSCs . The lattice strain in perovskite film has been proposed to impact ion migration, defect formation, and carrier dynamics in PSCs. Strain can be generated in perovskite films during device fabrication, thermal expansion, photostriction, electrostriction, or local lattice strain due to ionic size mismatch .…”

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confidence: 99%

“…Strain can be generated in perovskite films during device fabrication, thermal expansion, photostriction, electrostriction, or local lattice strain due to ionic size mismatch . While strain‐accelerated degradation of perovskite films is established, whether the light‐induced strain is the dominant driving force for degradation of perovskite solar cells still needs to be confirmed. Finally, the presence of excess photoexcited charge carriers has also been reported to accelerate ion migration in lead halide perovskite materials, hindering the stability of PSCs .…”

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confidence: 99%

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Synergistic Effect of Elevated Device Temperature and Excess Charge Carriers on the Rapid Light‐Induced Degradation of Perovskite Solar Cells

et al. 2019

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With power conversion efficiencies now reaching 24.2%, the major factor limiting efficient electricity generation using perovskite solar cells (PSCs) is their long‐term stability. In particular, PSCs have demonstrated rapid degradation under illumination, the driving mechanism of which is yet to be understood. It is shown that elevated device temperature coupled with excess charge carriers due to constant illumination is the dominant force in the rapid degradation of encapsulated perovskite solar cells under illumination. Cooling the device to 20 °C and operating at the maximum power point improves the stability of CH3NH3PbI3 solar cells over 100× compared to operation under open circuit conditions at 60 °C. Light‐induced strain originating from photothermal‐induced expansion is also observed in CH3NH3PbI3, which excludes other light‐induced‐strain mechanisms. However, strain and electric field do not appear to play any role in the initial rapid degradation of CH3NH3PbI3 solar cells under illumination. It is revealed that the formation of additional recombination centers in PSCs facilitated by elevated temperature and excess charge carriers ultimately results in rapid light‐induced degradation. Guidance on the best methods for measuring the stability of PSCs is also given.

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“…Furthermore, we performed similar temperaturedependent PL ( Figure S15, Supporting Information) and X-ray diffraction ( Figure S16, Supporting Information) measurements on mixed-cation (FA 0.80 MA 0.15 Cs 0.05 )Pb(I 0.83 Br 0.17 ) 3 samples (FA = formamidinium), which correspond to state-ofthe-art solar cell devices. [39,40] This work, focusing on low-temperature phase transitions, therefore provides unique insight into local strain properties, which ultimately lead to performance and stability issues at device operating temperatures. These observations are consistent with the FA-based samples exhibiting a more rigid lattice than their MA-counterparts, thereby inhibiting the phase transition and associated hysteresis effects in a similar manner to the constrained small grain samples.…”

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confidence: 99%

Influence of Grain Size on Phase Transitions in Halide Perovskite Films

Stavrakas

Zelewski

Frohna

et al. 2019

Advanced Energy Materials

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toward the optimization of perovskite thin film growth from simple precursors have improved the efficiency and stability of devices to a high quality standard and low cost, placing them on the verge of commercialization. [1][2][3][4][5][6] Nevertheless, a better understanding of what influences their crystalline structure is needed in order to achieve phase purity, manage defects, and ultimately achieve optimal device performances.The dramatic gain in solar cell device efficiency since 2012 is only one of the features making perovskites stand out among other photovoltaic materials. With a Young's modulus around 20 GPa, [7][8][9][10] perovskites are mechanically softer than most other PV materials such as silicon (>160 GPa), [11,12] GaAs (≈85 GPa), [13] CIGS (≈80 GPa), [14,15] and CdTe (≈40 GPa), [16,17] and their structure has been reported to be prone to light-induced, electric-fieldinduced, and temperature-dependent rearrangements. [18][19][20][21][22][23] The workhorse system studied to date, methylammonium lead iodide (MAPbI 3 ), is in a tetragonal phase (TP) at room temperature, but undergoes a transition to a cubic phase at high temperature (≈330 K) and an orthorhombic phase (OP) at low temperature (≈150 K). Recently, we and others [24][25][26] have reported that the structural rearrangement from TP to OP causes a distinct hysteretic change in optical and transport properties as well as device behavior between heating and cooling cycles. This hysteresis could be reduced by scraping the film from the substrate and instead measuring randomly oriented powder samples. [24] These results provide hints that the thermal stability [27] and phase transition can be influenced by the local environment of the film due to interactions between the material and substrate as well as within the bulk film itself. Unless understood and mitigated, such hysteretic changes at low temperature may limit the use of perovskite solar cells in some specific applications, for example, aerospace applications, which require operation at extremely low temperatures [28] (<200 K).State-of-the-art perovskite films are polycrystalline, which leads to microscale inhomogeneities in a number of properties such as morphology and defect distributions [29][30][31][32] and, in turn, to local variations in the electronic environment for charge carriers. Generally, increasing grain sizes in MAPbI 3 films has resulted in improvements in critical performance parameters, such as an increase in carrier mobility and charge collection efficiency, [33,34] along with smaller bandgaps, longer lifetimes, Grain size in polycrystalline halide perovskite films is known to have an impact on the optoelectronic properties of the films, but its influence on their soft structural properties and phase transitions is unclear. Here, temperature-dependent X-ray diffraction, absorption, and macro-and microphotoluminescence measurements are used to investigate the tetragonal to orthorhombic phase transition in thin methylammonium lead iodide films with grain sizes ranging fr...

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Lattice strain causes non-radiative losses in halide perovskites

Abstract: Halide perovskites are found to exhibit strain patterns over large areas, which influences the lifetimes of charge carriers.

Cited by 412 publications

References 50 publications

Efficient Organic Solar Cells with a High Open‐Circuit Voltage of 1.34 V

Efficient Organic Solar Cells with a High Open‐Circuit Voltage of 1.34 V

Synergistic Effect of Elevated Device Temperature and Excess Charge Carriers on the Rapid Light‐Induced Degradation of Perovskite Solar Cells

Influence of Grain Size on Phase Transitions in Halide Perovskite Films

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