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Title: Formation and Diffusion of Metal Impurities in Perovskite Solar Cell Material CH 3 NH 3 PbI 3 : Implications on Solar Cell Degradation and Choice of Electrode

Authors:
 [1];  [2];  [2];  [3]; ORCiD logo [1]
  1. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge TN 37831 USA
  2. Key Laboratory of Automobile Materials of MOE and Department of Materials Science and Engineering, Jilin University, Changchun 130012 China
  3. Key Laboratory of Automobile Materials of MOE and Department of Materials Science and Engineering, Jilin University, Changchun 130012 China, State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012 China
Publication Date:
Sponsoring Org.:
USDOE
OSTI Identifier:
1414958
Grant/Contract Number:
2016YFB0201204
Resource Type:
Journal Article: Published Article
Journal Name:
Advanced Science
Additional Journal Information:
Related Information: CHORUS Timestamp: 2017-12-27 03:26:12; Journal ID: ISSN 2198-3844
Publisher:
Wiley Blackwell (John Wiley & Sons)
Country of Publication:
Germany
Language:
English

Citation Formats

Ming, Wenmei, Yang, Dongwen, Li, Tianshu, Zhang, Lijun, and Du, Mao-Hua. Formation and Diffusion of Metal Impurities in Perovskite Solar Cell Material CH 3 NH 3 PbI 3 : Implications on Solar Cell Degradation and Choice of Electrode. Germany: N. p., 2017. Web. doi:10.1002/advs.201700662.
Ming, Wenmei, Yang, Dongwen, Li, Tianshu, Zhang, Lijun, & Du, Mao-Hua. Formation and Diffusion of Metal Impurities in Perovskite Solar Cell Material CH 3 NH 3 PbI 3 : Implications on Solar Cell Degradation and Choice of Electrode. Germany. doi:10.1002/advs.201700662.
Ming, Wenmei, Yang, Dongwen, Li, Tianshu, Zhang, Lijun, and Du, Mao-Hua. 2017. "Formation and Diffusion of Metal Impurities in Perovskite Solar Cell Material CH 3 NH 3 PbI 3 : Implications on Solar Cell Degradation and Choice of Electrode". Germany. doi:10.1002/advs.201700662.
@article{osti_1414958,
title = {Formation and Diffusion of Metal Impurities in Perovskite Solar Cell Material CH 3 NH 3 PbI 3 : Implications on Solar Cell Degradation and Choice of Electrode},
author = {Ming, Wenmei and Yang, Dongwen and Li, Tianshu and Zhang, Lijun and Du, Mao-Hua},
abstractNote = {},
doi = {10.1002/advs.201700662},
journal = {Advanced Science},
number = ,
volume = ,
place = {Germany},
year = 2017,
month =
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1002/advs.201700662

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  • CH 3NH 3PbI 3-based solar cells have shown remarkable progress in recent years but have also suffered from structural, electrical, and chemical instabilities related to the soft lattices and the chemistry of these halides. One of the instabilities is ion migration, which may cause current–voltage hysteresis in CH 3NH 3PbI 3 solar cells. Significant ion diffusion and ionic conductivity in CH 3NH 3PbI 3 have been reported; their nature, however, remain controversial. In the literature, the use of different experimental techniques leads to the observation of different diffusing ions (either iodine or CH 3NH 3 ion); the calculated diffusion barriersmore » for native defects scatter in a wide range; the calculated defect formation energies also differ qualitatively. These controversies hinder the understanding and the control of the ion migration in CH 3NH 3PbI 3. In this paper, we show density functional theory calculations of both the diffusion barriers and the formation energies for native defects (V I +, MA i +, V MA , and I i ) and the Au impurity in CH 3NH 3PbI 3. V I + is found to be the dominant diffusing defect due to its low formation energy and the low diffusion barrier. I i and MA i + also have low diffusion barriers but their formation energies are relatively high. The hopping rate of V I + is further calculated taking into account the contribution of the vibrational entropy, confirming V I + as a fast diffuser. We discuss approaches for managing defect population and migration and suggest that chemically modifying surfaces, interfaces, and grain boundaries may be effective in controlling the population of the iodine vacancy and the device polarization. We further show that the formation energy and the diffusion barrier of Au interstitial in CH 3NH 3PbI 3 are both low. As a result, it is thus possible that Au can diffuse into CH3NH3PbI3 under bias in devices (e.g., solar cell, photodetector) with Au/CH 3NH 3PbI 3 interfaces and modify the electronic properties of CH 3NH 3PbI 3.« less
  • CH 3NH 3PbI 3-based solar cells have shown remarkable progress in recent years but have also suffered from structural, electrical, and chemical instabilities related to the soft lattices and the chemistry of these halides. One of the instabilities is ion migration, which may cause current–voltage hysteresis in CH 3NH 3PbI 3 solar cells. Significant ion diffusion and ionic conductivity in CH 3NH 3PbI 3 have been reported; their nature, however, remain controversial. In the literature, the use of different experimental techniques leads to the observation of different diffusing ions (either iodine or CH 3NH 3 ion); the calculated diffusion barriersmore » for native defects scatter in a wide range; the calculated defect formation energies also differ qualitatively. These controversies hinder the understanding and the control of the ion migration in CH 3NH 3PbI 3. In this paper, we show density functional theory calculations of both the diffusion barriers and the formation energies for native defects (V I +, MA i +, V MA , and I i ) and the Au impurity in CH 3NH 3PbI 3. V I + is found to be the dominant diffusing defect due to its low formation energy and the low diffusion barrier. I i and MA i + also have low diffusion barriers but their formation energies are relatively high. The hopping rate of V I + is further calculated taking into account the contribution of the vibrational entropy, confirming V I + as a fast diffuser. We discuss approaches for managing defect population and migration and suggest that chemically modifying surfaces, interfaces, and grain boundaries may be effective in controlling the population of the iodine vacancy and the device polarization. We further show that the formation energy and the diffusion barrier of Au interstitial in CH 3NH 3PbI 3 are both low. As a result, it is thus possible that Au can diffuse into CH3NH3PbI3 under bias in devices (e.g., solar cell, photodetector) with Au/CH 3NH 3PbI 3 interfaces and modify the electronic properties of CH 3NH 3PbI 3.« less
  • Methylammonium (MA) lead triiodide (MAPbI 3) has recently emerged as a promising solar cell material. But, MAPbI3 is known to have chemical instability, i.e., MAPbI3 is prone to decomposition into MAI and PbI 2 even at moderate temperatures (e.g. 330 K). Here, we show that the chemical instability, as reflected by the calculated negligible enthalpy of formation of MAPbI 3 (with respect to MAI and PbI 2), has an unusual and important consequence for defect properties, i.e., defect formation energies in low-carrier-density MAPbI 3 are nearly independent of the chemical potentials of constituent elements and thus can be uniquely determined. This allows straightforward calculations of defect concentrations and the activation energy of ionic conductivity (the sum of the formation energy and the diffusion barrier of the charged mobile defect) in MAPbI 3. Furthermore, the calculated activation energy for ionic conductivity due to Vmore » $$+\atop{1}$$ diffusion is in excellent agreement with the experimental values, which demonstrates unambiguously that V$$+\atop{1}$$ is the dominant diffusing defect and is responsible for the observed ion migration and device polarization in MAPbI3 solar cells. The calculated low formation energy of a Frenkel pair (V$$+\atop{1}$$ -I$$-\atop{i}$$ and low diffusion barriers of V$$+\atop{1}$$ and Image I$$-\atop{i}$$ suggest that the iodine ion migration and the resulting device polarization may occur even in single-crystal devices and grain-boundary-passivated polycrystalline thin film devices (which were previously suggested to be free from ion-migration-induced device polarization), leading to device degradation. Moreover, the device polarization due to the Frenkel pair (which has a relatively low concentration) may take a long time to develop and thus may avoid the appearance of the current–voltage hysteresis at typical scan rates.« less
  • We have investigated the gettering of transition metals in multicrystalline silicon wafers during a phosphorus emitter diffusion for solar cell processing. The results show that mainly regions of high initial recombination lifetime exhibit a significant lifetime enhancement upon phosphorus diffusion gettering. Nevertheless, transition metal profiles extracted by secondary ion mass spectrometry in a region of low initial lifetime reveal significant gradients in Cr, Fe, and Cu concentrations towards the surface after the emitter diffusion, without exhibiting a significant enhancement in the lifetime. In a region of higher initial lifetime, however, diminutive concentration gradients of the transition metal impurities are revealed,more » indicating a significantly lower initial concentration in these regions. From spatial maps of the dislocation density in the wafers, we find that lifetime enhancements mainly occur in regions of low dislocation density. Thus, it is believed that a generally higher concentration of transition metals combined with an impurity decoration of dislocations in regions of high dislocation density limit the initial lifetime and the lifetime after the phosphorus diffusion, in spite of the notable gettering of transition metal impurities towards the surface in these regions. Furthermore, after a hydrogen release from overlying silicon nitride layers, we observe that only regions of low dislocation density experience a significant lifetime enhancement. This is attributed to impurity decoration of the dislocations in the regions of both high dislocation density and high transition metal impurity concentration, reducing the ability of hydrogen to passivate dislocations in these regions.« less