Organic-inorganic halide perovskites ( are currently intensively studied due to their outstanding optoelectronic properties and relatively low cost production They are prominent materials for photovoltaics and also have substantial potential for applications such as LEDs and photodetectors 1 Several previous studies have observed I V hysteresis ascribed to interfacial charge accumulation 2 4 For further development of OIHP devices a deeper understanding of charge dynamics is needed to suppress unfavourable effects In this work, we studied space charge formation in the MAPb Br 3 detector (University Grenoble 5 with Cr/Cr 100 nm/ 30 nm) contacts using the laser induced transient current technique (L TCT) and time resolved I V characteristics.
For longer depolarization time, only formation of negative space charge region beneath anode is observed. DT=1s either completely suppresses or significantly slows down cathode barrier formation. Cathode barrier suppression combined with a weak I-V hysteresis for the same pulsing parameters suggest that cathode barrier is leading cause of I-V hysteresis. This would also mean that electron transport is dominant in this sample Pulsing parameter testing Time resolved I-V characteristic
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Sample relaxation Fig. 4: Current relaxation for DT=100ms and BPW=1ms. b) I-V characteristics constructed from current relaxations at 180s for various pulsing parameter. Fig. 7: Hole waveform relaxation after a) DT=100ms BPW=1ms and b) DT=1s BPW=1ms Both polarization states are fully reversible. Polarization induced by DT=100ms BPW=1ms, however, needs longer time for full relaxation. Long depolarization time results to weak (red curve) or no hysteresis (grey) of I-V curve. Strong hysteresis (blue) for DT=100ms is consistent with either lowering of electric field beneath control electrode or with barrier formation. This measurement alone cannot distinguish these models so L-TCT is also employed for sample investigation. Conclusion
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References We have observed that formation of cathode barrier is responsible for I-V hysteresis. Obtained results indicate that electron transport is dominant in this sample. This result agrees with that of . M. Ahmadi, L. Collins, K. Higgins, D. Kim, E. Lukosi, and S. V. Kalinin, Spatially Resolved Carrier Dynamics at MAPbBr3 Single Crystal Electrode Interface, ACS Appl. Mater. Interfaces, vol. 11, no. 44, pp. 4155141560, Nov. 2019 We propose three models to describe the observed space charge formation C. Li et al., Iodine Migration and its Effect on Hysteresis in Perovskite Solar Cells, Adv. Mater., vol. 28, no. 12, pp. 24462454, 2016, W. Tress, Metal Halide Perovskites as Mixed ElectronicIonic Conductors: Challenges and OpportunitiesFrom Hysteresis to 1. Ion-induced barrier leads to electron (hole) depletion, which subsequently leads to formation of positive (negative) space charge beneath cathode (anode).
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Memristivity, J. Phys. Chem. Lett., vol. 8, no. 13, pp. 31063114, Jul. 2017, doi: 10.1021/acs.jpclett.7b00975. S. A. L. Weber et al., How the formation of interfacial charge causes hysteresis in perovskite solar cells, Energy Environ. Sci., vol. 11, no. 9, pp. 24042413, Sep. 2018 2. Space charge is purely formed by movement of ions in the sample. 3. Combination of the previous two. S. Amari, J.-M. Verilhac, E. Gros DAillon, A. Ibanez, J. Zaccaro, Optimization of the Growth Conditions for High Quality CH3NH3PbBr3 Hybrid Perovskite Single Crystals, Cryst. Growth Des. 2020, 20, 1665 In all models the cathode barrier formation and I-V hysteresis can be suppressed with sufficient depolarization time. Garca-Batlle, M., Baussens, O., Amari, S., Zaccaro, J., Gros-Daillon, E., Verilhac, J.-M., Guerrero, A., Garcia-Belmonte, G., Moving Ions Vary Electronic Conductivity in Lead Bromide Perovskite Single Crystals through Dynamic Doping. Adv. Electron. Mater. 2020, 6, 2000485.
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