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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. In this paper, 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. Finally, 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.

Authors:
ORCiD logo [1];  [2];  [1];  [2];  [3]; ORCiD logo [3];  [2];  [1]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Univ. of Oregon, Eugene, OR (United States)
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES); LBNL Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1379750
Grant/Contract Number:  
AC02-05CH11231; SC0012363
Resource Type:
Accepted Manuscript
Journal Name:
ACS Energy Letters
Additional Journal Information:
Journal Volume: 2; Journal Issue: 3; Journal ID: ISSN 2380-8195
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE

Citation Formats

Sutter-Fella, Carolin M., Miller, D. Westley, Ngo, Quynh P., Roe, Ellis T., Toma, Francesca M., Sharp, Ian D., Lonergan, Mark C., and Javey, Ali. Band Tailing and Deep Defect States in CH3NH3Pb(I1–xBrx)3 Perovskites As Revealed by Sub-Bandgap Photocurrent. United States: N. p., 2017. Web. https://doi.org/10.1021/acsenergylett.6b00727.
Sutter-Fella, Carolin M., Miller, D. Westley, Ngo, Quynh P., Roe, Ellis T., Toma, Francesca M., Sharp, Ian D., Lonergan, Mark C., & Javey, Ali. Band Tailing and Deep Defect States in CH3NH3Pb(I1–xBrx)3 Perovskites As Revealed by Sub-Bandgap Photocurrent. United States. https://doi.org/10.1021/acsenergylett.6b00727
Sutter-Fella, Carolin M., Miller, D. Westley, Ngo, Quynh P., Roe, Ellis T., Toma, Francesca M., Sharp, Ian D., Lonergan, Mark C., and Javey, Ali. Wed . "Band Tailing and Deep Defect States in CH3NH3Pb(I1–xBrx)3 Perovskites As Revealed by Sub-Bandgap Photocurrent". United States. https://doi.org/10.1021/acsenergylett.6b00727. https://www.osti.gov/servlets/purl/1379750.
@article{osti_1379750,
title = {Band Tailing and Deep Defect States in CH3NH3Pb(I1–xBrx)3 Perovskites As Revealed by Sub-Bandgap Photocurrent},
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 Javey, Ali},
abstractNote = {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. In this paper, 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. Finally, 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.},
doi = {10.1021/acsenergylett.6b00727},
journal = {ACS Energy Letters},
number = 3,
volume = 2,
place = {United States},
year = {2017},
month = {2}
}

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