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It Takes Two to Tango - Double-Layer Selective Contacts in Perovskite Solar Cells for Improved Device Performance and Reduced Hysteresis

Kegelmann, Lukas; Wolff, Christian M.; Awino, Celline; Lang, Felix; Unger, Eva L. LU ; Korte, Lars; Dittrich, Thomas; Neher, Dieter; Rech, Bernd and Albrecht, Steve (2017) In ACS Applied Materials and Interfaces 9(20). p.17245-17255
Abstract

Solar cells made from inorganic-organic perovskites have gradually approached market requirements as their efficiency and stability have improved tremendously in recent years. Planar low-temperature processed perovskite solar cells are advantageous for possible large-scale production but are more prone to exhibiting photocurrent hysteresis, especially in the regular n-i-p structure. Here, a systematic characterization of different electron selective contacts with a variety of chemical and electrical properties in planar n-i-p devices processed below 180 °C is presented. The inorganic metal oxides TiO2 and SnO2, the organic fullerene derivatives C60, PCBM, and ICMA, as well as double-layers with a metal... (More)

Solar cells made from inorganic-organic perovskites have gradually approached market requirements as their efficiency and stability have improved tremendously in recent years. Planar low-temperature processed perovskite solar cells are advantageous for possible large-scale production but are more prone to exhibiting photocurrent hysteresis, especially in the regular n-i-p structure. Here, a systematic characterization of different electron selective contacts with a variety of chemical and electrical properties in planar n-i-p devices processed below 180 °C is presented. The inorganic metal oxides TiO2 and SnO2, the organic fullerene derivatives C60, PCBM, and ICMA, as well as double-layers with a metal oxide/PCBM structure are used as electron transport materials (ETMs). Perovskite layers deposited atop the different ETMs with the herein applied fabrication method show a similar morphology according to scanning electron microscopy. Further, surface photovoltage spectroscopy measurements indicate comparable perovskite absorber qualities on all ETMs, except TiO2, which shows a more prominent influence of defect states. Transient photoluminescence studies together with current-voltage scans over a broad range of scan speeds reveal faster charge extraction, less pronounced hysteresis effects, and higher efficiencies for devices with fullerene compared to those with metal oxide ETMs. Beyond this, only double-layer ETM structures substantially diminish hysteresis effects for all performed scan speeds and strongly enhance the power conversion efficiency up to a champion stabilized value of 18.0%. The results indicate reduced recombination losses for a double-layer TiO2/PCBM contact design: First, a reduction of shunt paths through the fullerene to the ITO layer. Second, an improved hole blocking by the wide band gap metal oxide. Third, decreased transport losses due to an energetically more favorable contact, as implied by photoelectron spectroscopy measurements. The herein demonstrated improvements of multilayer selective contacts may serve as a general design guideline for perovskite solar cells.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
double-layer, electron contact, fullerene, hysteresis, metal oxide, perovskite solar cell, regular planar architecture
in
ACS Applied Materials and Interfaces
volume
9
issue
20
pages
11 pages
publisher
The American Chemical Society
external identifiers
  • scopus:85019655197
  • wos:000402498600056
ISSN
1944-8244
DOI
10.1021/acsami.7b00900
language
English
LU publication?
yes
id
07d2c157-df88-4cc2-b94a-06bdc38893bd
date added to LUP
2017-06-08 14:27:13
date last changed
2018-01-07 12:06:43
@article{07d2c157-df88-4cc2-b94a-06bdc38893bd,
  abstract     = {<p>Solar cells made from inorganic-organic perovskites have gradually approached market requirements as their efficiency and stability have improved tremendously in recent years. Planar low-temperature processed perovskite solar cells are advantageous for possible large-scale production but are more prone to exhibiting photocurrent hysteresis, especially in the regular n-i-p structure. Here, a systematic characterization of different electron selective contacts with a variety of chemical and electrical properties in planar n-i-p devices processed below 180 °C is presented. The inorganic metal oxides TiO<sub>2</sub> and SnO<sub>2</sub>, the organic fullerene derivatives C<sub>60</sub>, PCBM, and ICMA, as well as double-layers with a metal oxide/PCBM structure are used as electron transport materials (ETMs). Perovskite layers deposited atop the different ETMs with the herein applied fabrication method show a similar morphology according to scanning electron microscopy. Further, surface photovoltage spectroscopy measurements indicate comparable perovskite absorber qualities on all ETMs, except TiO<sub>2</sub>, which shows a more prominent influence of defect states. Transient photoluminescence studies together with current-voltage scans over a broad range of scan speeds reveal faster charge extraction, less pronounced hysteresis effects, and higher efficiencies for devices with fullerene compared to those with metal oxide ETMs. Beyond this, only double-layer ETM structures substantially diminish hysteresis effects for all performed scan speeds and strongly enhance the power conversion efficiency up to a champion stabilized value of 18.0%. The results indicate reduced recombination losses for a double-layer TiO<sub>2</sub>/PCBM contact design: First, a reduction of shunt paths through the fullerene to the ITO layer. Second, an improved hole blocking by the wide band gap metal oxide. Third, decreased transport losses due to an energetically more favorable contact, as implied by photoelectron spectroscopy measurements. The herein demonstrated improvements of multilayer selective contacts may serve as a general design guideline for perovskite solar cells.</p>},
  author       = {Kegelmann, Lukas and Wolff, Christian M. and Awino, Celline and Lang, Felix and Unger, Eva L. and Korte, Lars and Dittrich, Thomas and Neher, Dieter and Rech, Bernd and Albrecht, Steve},
  issn         = {1944-8244},
  keyword      = {double-layer,electron contact,fullerene,hysteresis,metal oxide,perovskite solar cell,regular planar architecture},
  language     = {eng},
  month        = {05},
  number       = {20},
  pages        = {17245--17255},
  publisher    = {The American Chemical Society},
  series       = {ACS Applied Materials and Interfaces},
  title        = {It Takes Two to Tango - Double-Layer Selective Contacts in Perovskite Solar Cells for Improved Device Performance and Reduced Hysteresis},
  url          = {http://dx.doi.org/10.1021/acsami.7b00900},
  volume       = {9},
  year         = {2017},
}