TY - JOUR
T1 - Interface-dependent ion migration/accumulation controls hysteresis in MAPbI3 solar cells
AU - Levine, Igal
AU - Nayak, Pabitra K.
AU - Wang, Jacob Tse Wei
AU - Sakai, Nobuya
AU - Van Reenen, Stephan
AU - Brenner, Thomas M.
AU - Mukhopadhyay, Sabyasachi
AU - Snaith, Henry J.
AU - Hodes, Gary
AU - Cahen, David
N1 - Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/8/4
Y1 - 2016/8/4
N2 - Hysteresis in the current-voltage characteristics of hybrid organic-inorganic perovskite-based solar cells is one of the fundamental aspects of these cells that we do not understand well. One possible cause, suggested for the hysteresis, is polarization of the perovskite layer under applied voltage and illumination bias, due to ion migration within the perovskite. To study this problem systemically, current-voltage characteristics of both regular (light incident through the electron conducting contact) and so-called inverted (light incident through the hole conducting contact) perovskite cells were studied at different temperatures and scan rates. We explain our results by assuming that the effects of scan rate and temperature on hysteresis are strongly correlated to ion migration within the device, with the rate-determining step being ion migration at/across the interfaces of the perovskite layer with the contact materials. By correlating between the scan rate with the measurement temperature, we show that the inverted and regular cells operate in different hysteresis regimes, with different activation energies of 0.28 ± 0.04 eV and 0.59 ± 0.09 eV, respectively. We suggest that the differences observed between the two architectures are due to different rates of ion migration close to the interfaces, and conclude that the diffusion coefficient of migrating ions in the inverted cells is 3 orders of magnitude higher than in the regular cells, leading to different accumulation rates of ions near the interfaces. Analysis of VOC as a function of temperature shows that the main recombination mechanism is trap-assisted (Shockley-Read Hall, SRH) in the space charge region, similar to what is the case for other thin film inorganic solar cells.
AB - Hysteresis in the current-voltage characteristics of hybrid organic-inorganic perovskite-based solar cells is one of the fundamental aspects of these cells that we do not understand well. One possible cause, suggested for the hysteresis, is polarization of the perovskite layer under applied voltage and illumination bias, due to ion migration within the perovskite. To study this problem systemically, current-voltage characteristics of both regular (light incident through the electron conducting contact) and so-called inverted (light incident through the hole conducting contact) perovskite cells were studied at different temperatures and scan rates. We explain our results by assuming that the effects of scan rate and temperature on hysteresis are strongly correlated to ion migration within the device, with the rate-determining step being ion migration at/across the interfaces of the perovskite layer with the contact materials. By correlating between the scan rate with the measurement temperature, we show that the inverted and regular cells operate in different hysteresis regimes, with different activation energies of 0.28 ± 0.04 eV and 0.59 ± 0.09 eV, respectively. We suggest that the differences observed between the two architectures are due to different rates of ion migration close to the interfaces, and conclude that the diffusion coefficient of migrating ions in the inverted cells is 3 orders of magnitude higher than in the regular cells, leading to different accumulation rates of ions near the interfaces. Analysis of VOC as a function of temperature shows that the main recombination mechanism is trap-assisted (Shockley-Read Hall, SRH) in the space charge region, similar to what is the case for other thin film inorganic solar cells.
UR - http://www.scopus.com/inward/record.url?scp=84980583034&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.6b04233
DO - 10.1021/acs.jpcc.6b04233
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AN - SCOPUS:84980583034
SN - 1932-7447
VL - 120
SP - 16399
EP - 16411
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 30
ER -