Title: Optoelectronic Quality and Stability of Hybrid Perovskites from MAPbI ₃ to MAPbI ₂ Br Using Composition Spread Libraries

Abstract

The development of stable high-bandgap hybrid perovskites (HPs) with high optoelectronic quality may enable tandem solar cells with power conversion efficiencies approaching 30%. The halide composition of HPs has been observed to effect bandgap, carrier lifetime, and material stability. Here we report optoelectronic quality and stability under illumination of thousands of compositions ranging from the pure iodide (CH3NH3PbI3) to the diiodomonobromide (CH3NH3PbI2Br). Hyperspectral maps of steady-state absolute intensity photoluminescence (AIPL) are used to determine the quasi-Fermi level splitting (QFLS) at each point after synthesis. The QFLS upon first illumination increases with bandgap and reaches a maximum of 1.27 eV under 1 sun illumination intensity for a bandgap of 1.75 eV. However, the optoelectronic quality (χ), defined as the ratio of the QFLS to the maximum theoretical QFLS for bandgap, decreases with bandgap from around 88% for 1.60 eV bandgap down to 82% for 1.84 eV bandgap. Further, we show that a reversible light induced defect forms that reduces the optoelectronic quality, particularly for high-bandgap materials. Composition analysis shows that the halide to lead ratio, (I + Br)/Pb, decreases from 3 for the pure iodide to 2.5 for the diiodomonobromide, suggesting a role of halide vacancies or halide substitution defects inmore » the light-induced instability for this synthesis route. Even with the light-induced defect, a stable QFLS of about 1.17 eV is possible. Comparing our QFLS to Voc values from HP devices reported in the literature indicates that higher open circuit voltages are possible but may require optimization of band alignment. Further, the spectral shape of the PL emission is found to be more commensurate with Franz–Keldysh broadening from local electric fields or from a screened Thomas–Fermi density of states (as opposed to a joint density of states due to Urbach disorder).« less

Authors:

Braly, Ian L. ^[1]; Hillhouse, Hugh W. ^[1]

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+ Show Author Affiliations

1. Univ. of Washington, Seattle, WA (United States)

Publication Date:

Tue Dec 22 00:00:00 EST 2015

Research Org.:

Univ. of Washington, Seattle, WA (United States)

Sponsoring Org.:

USDOE Office of Energy Efficiency and Renewable Energy (EERE)

Contributing Org.:

Clean Energy Institute

OSTI Identifier:

1343430

Report Number(s):

DOE-UW-Braly Hillhouse-1
Journal ID: ISSN 1932-7447

Grant/Contract Number:  

EE0006710

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Physical Chemistry. C

Additional Journal Information:

Journal Volume: 120; Journal Issue: 2; Journal ID: ISSN 1932-7447

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

14 SOLAR ENERGY; Hybrid Perovskites; High bandgap; Photoluminescence