What Limits the Open-Circuit Voltage of Bromide Perovskite-Based Solar Cells?

Arava Zohar, Michael Kulbak, Igal Levine, Gary Hodes, Antoine Kahn, David Cahen

Research output: Contribution to journalArticlepeer-review

68 Scopus citations

Abstract

High band gap Pb bromide perovskite (APbBr 3 )-based solar cells, where A is a mixture of formamidinium, methylammonium, and Cs, show significantly higher, relative, V OC losses than their iodide analogs. Using photoluminescence-, quantum efficiency-, and surface photovoltage-spectroscopy measurements, we show the absence of any significant electronically active tail states within the bulk of the (FA 0.85 MA 0.1 Cs 0.05 )PbBr 3 absorber. All methods confirm that E G = 2.28 eV for this halide perovskite, HaP. Contact potential difference measurements for this HaP, on different substrates, reveal a Z-shape dependence between the substrate work functions and that of the HaP, deposited on it, indicating that the HaP is relatively low doped and that its Fermi level is affected by the substrate onto which it is deposited. We confirm results from electron beam-induced current (EBIC) and other measurements that most voltage loss of cells, made with these HaP films, is at the HaP/selective-contact interface, specifically the TiO 2 /HaP one, and provide a complete account of these cells' V OC losses. Capacitance measurements indicate that 350 mV V OC could be gained by eliminating (fast) interfacial states, emphasizing the importance of interface passivation. Still, even passivating the TiO 2 /HaP interface cannot eliminate the band misalignment with Br-based HaPs.

Original languageEnglish
Pages (from-to)1-7
Number of pages7
JournalACS Energy Letters
Volume4
Issue number1
DOIs
StatePublished - 11 Jan 2019
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2018 American Chemical Society.

Funding

We thank Dr. T. Dittrich (HZB) for collaboration on the SPS measurements and Dr. Pabitra K. Nayak for fruitful discussions. We acknowledge support by US-Israel Binational Science Foundation (BSF-Grant No. 2014357) and the Ullmann Family Foundation (@Weizmann Institute), for partial support. D.C. held the Schaefer Chair in Energy Research.

FundersFunder number
US-Israel Binational Science Foundation2014357
Ullmann Family Foundation

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