Band tailing and deep defect states in CH3NH3Pb(I1-xBrx)3 perovskites as revealed by sub-bandgap photocurrent

Carolin M. Sutter-Fella; D. Westley Miller; Quynh P. Ngo; Ellis T. Roe; Francesca M. Toma; Ian D. Sharp; Mark C. Lonergan; Ali Javey

doi:10.1021/acsenergylett.6b00727

Band tailing and deep defect states in CH₃NH₃Pb(I_1-xBr_x)₃ perovskites as revealed by sub-bandgap photocurrent

Carolin M. Sutter-Fella, D. Westley Miller, Quynh P. Ngo, Ellis T. Roe, Francesca M. Toma, Ian D. Sharp, Mark C. Lonergan, Ali Javey

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123 Scopus citations

Abstract

Organometal halide perovskite semiconductors have emerged as promising candidates for optoelectronic applications because of the outstanding charge carrier transport properties, achieved with low-temperature synthesis. Here, we present highly sensitive sub-bandgap external quantum efficiency (EQE) measurements of Au/spiro-OMeTAD/CH₃NH₃Pb(I_1-xBr_x)₃/TiO₂/FTO/glass photovoltaic devices. The room-temperature spectra show exponential band tails with a sharp onset characterized by low Urbach energies (Eu) over the full halide composition space. The Urbach energies are 15-23 meV, lower than those for most semiconductors with similar bandgaps (especially with Eg > 1.9 eV). Intentional aging of CH₃NH₃Pb(I_1-xBr_x)₃ for up to 2300 h, reveals no change in Eu, despite the appearance of the PbI₂ phase due to decomposition, and confirms a high degree of crystal ordering. Moreover, sub-bandgap EQE measurements reveal an extended band of sub-bandgap electronic states that can be fit with one or two point defects for pure CH₃NH₃PbI₃ or mixed CH₃NH₃Pb(I_1-xBr_x)₃ compositions, respectively. The study provides experimental evidence of defect states close to the midgap that could impact photocarrier recombination and energy conversion efficiency in higher bandgap CH₃NH₃Pb(I_1-xBr_x)₃ alloys.

Original language	English
Pages (from-to)	709-715
Number of pages	7
Journal	ACS Energy Letters
Volume	2
Issue number	3
DOIs	https://doi.org/10.1021/acsenergylett.6b00727
State	Published - 10 Mar 2017
Externally published	Yes

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title = "Band tailing and deep defect states in CH3NH3Pb(I1-xBrx)3 perovskites as revealed by sub-bandgap photocurrent",

abstract = "Organometal halide perovskite semiconductors have emerged as promising candidates for optoelectronic applications because of the outstanding charge carrier transport properties, achieved with low-temperature synthesis. Here, we present highly sensitive sub-bandgap external quantum efficiency (EQE) measurements of Au/spiro-OMeTAD/CH3NH3Pb(I1-xBrx)3/TiO2/FTO/glass photovoltaic devices. The room-temperature spectra show exponential band tails with a sharp onset characterized by low Urbach energies (Eu) over the full halide composition space. The Urbach energies are 15-23 meV, lower than those for most semiconductors with similar bandgaps (especially with Eg > 1.9 eV). Intentional aging of CH3NH3Pb(I1-xBrx)3 for up to 2300 h, reveals no change in Eu, despite the appearance of the PbI2 phase due to decomposition, and confirms a high degree of crystal ordering. Moreover, sub-bandgap EQE measurements reveal an extended band of sub-bandgap electronic states that can be fit with one or two point defects for pure CH3NH3PbI3 or mixed CH3NH3Pb(I1-xBrx)3 compositions, respectively. The study provides experimental evidence of defect states close to the midgap that could impact photocarrier recombination and energy conversion efficiency in higher bandgap CH3NH3Pb(I1-xBrx)3 alloys.",

author = "Sutter-Fella, {Carolin M.} and Miller, {D. Westley} and Ngo, {Quynh P.} and Roe, {Ellis T.} and Toma, {Francesca M.} and Sharp, {Ian D.} and Lonergan, {Mark C.} and Ali Javey",

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doi = "10.1021/acsenergylett.6b00727",

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T1 - Band tailing and deep defect states in CH3NH3Pb(I1-xBrx)3 perovskites as revealed by sub-bandgap photocurrent

AU - Sutter-Fella, Carolin M.

AU - Miller, D. Westley

AU - Ngo, Quynh P.

AU - Roe, Ellis T.

AU - Toma, Francesca M.

AU - Sharp, Ian D.

AU - Lonergan, Mark C.

AU - Javey, Ali

PY - 2017/3/10

Y1 - 2017/3/10

N2 - Organometal halide perovskite semiconductors have emerged as promising candidates for optoelectronic applications because of the outstanding charge carrier transport properties, achieved with low-temperature synthesis. Here, we present highly sensitive sub-bandgap external quantum efficiency (EQE) measurements of Au/spiro-OMeTAD/CH3NH3Pb(I1-xBrx)3/TiO2/FTO/glass photovoltaic devices. The room-temperature spectra show exponential band tails with a sharp onset characterized by low Urbach energies (Eu) over the full halide composition space. The Urbach energies are 15-23 meV, lower than those for most semiconductors with similar bandgaps (especially with Eg > 1.9 eV). Intentional aging of CH3NH3Pb(I1-xBrx)3 for up to 2300 h, reveals no change in Eu, despite the appearance of the PbI2 phase due to decomposition, and confirms a high degree of crystal ordering. Moreover, sub-bandgap EQE measurements reveal an extended band of sub-bandgap electronic states that can be fit with one or two point defects for pure CH3NH3PbI3 or mixed CH3NH3Pb(I1-xBrx)3 compositions, respectively. The study provides experimental evidence of defect states close to the midgap that could impact photocarrier recombination and energy conversion efficiency in higher bandgap CH3NH3Pb(I1-xBrx)3 alloys.

AB - Organometal halide perovskite semiconductors have emerged as promising candidates for optoelectronic applications because of the outstanding charge carrier transport properties, achieved with low-temperature synthesis. Here, we present highly sensitive sub-bandgap external quantum efficiency (EQE) measurements of Au/spiro-OMeTAD/CH3NH3Pb(I1-xBrx)3/TiO2/FTO/glass photovoltaic devices. The room-temperature spectra show exponential band tails with a sharp onset characterized by low Urbach energies (Eu) over the full halide composition space. The Urbach energies are 15-23 meV, lower than those for most semiconductors with similar bandgaps (especially with Eg > 1.9 eV). Intentional aging of CH3NH3Pb(I1-xBrx)3 for up to 2300 h, reveals no change in Eu, despite the appearance of the PbI2 phase due to decomposition, and confirms a high degree of crystal ordering. Moreover, sub-bandgap EQE measurements reveal an extended band of sub-bandgap electronic states that can be fit with one or two point defects for pure CH3NH3PbI3 or mixed CH3NH3Pb(I1-xBrx)3 compositions, respectively. The study provides experimental evidence of defect states close to the midgap that could impact photocarrier recombination and energy conversion efficiency in higher bandgap CH3NH3Pb(I1-xBrx)3 alloys.

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Band tailing and deep defect states in CH₃NH₃Pb(I_1-xBr_x)₃ perovskites as revealed by sub-bandgap photocurrent

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