Achieving a High Open-Circuit Voltage in Inverted Wide-Bandgap Perovskite Solar Cells with a Graded Perovskite Homojunction

Chuanxiao Xiao, Chun Sheng Jiang, Mowafak Al-Jassim, Kai Zhu, Cong Chen, Zhaoning Song, Dewei Zhao, Niraj Shrestha, Chongwen Li, Guang Yang, Fang Yao, Xiaolu Zheng, Randy Ellingson, Guojia Fang, Yanfa Yan

Research output: Contribution to journalArticlepeer-review

149 Scopus Citations


Wide-bandgap (∼1.7–1.8 eV) perovskite solar cells have attracted substantial research interest in recent years due to their great potential to fabricate efficient tandem solar cells via combining with a lower bandgap (1.1–1.3 eV) absorber (e.g., Si, copper indium gallium diselenide, or low-bandgap perovskite). However, wide-bandgap perovskite solar cells usually suffer from large open circuit voltage (Voc) deficits caused by small grain sizes and photoinduced phase segregation. Here, we demonstrate that in addition to large grain sizes and passivated grain boundaries, controlling interface properties is critical for achieving high Voc's in the inverted wide-bandgap perovskite solar cells. We adopt guanidinium bromide solution to tune the effective doping and electronic properties of the surface layer of perovskite thin films, leading to the formation of a graded perovskite homojunction. The enhanced electric field at the perovskite homojunction is revealed by Kelvin probe force microscopy measurements. This advance enables an increase in the Voc of the inverted perovskite solar cells from an initial 1.12 V to 1.24 V. With the optimization of the device fabrication process, the champion inverted wide-bandgap cell delivers a power conversion efficiency of 18.19% and sustains more than 72% of its initial efficiency after continuous illumination for 70 h without encapsulation. Additionally, a semitransparent device with an indium tin oxide back contact retains more than 88% of its initial efficiency after 100 h maximum power point tracking.

Original languageAmerican English
Pages (from-to)141-147
Number of pages7
JournalNano Energy
StatePublished - 2019

Bibliographical note

Publisher Copyright:
© 2019 Elsevier Ltd

NREL Publication Number

  • NREL/JA-5K00-73656


  • Guanidinium bromide
  • Perovskite homojunction
  • Wide-bandgap perovskite solar cells


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