Ethylenediamine addition improves performance and suppresses phase instabilities in mixed-halide perovskites

DOI: 10.1021/acsenergylett.2c01998

Authors: Margherita Taddei (University of Washington) , Joel A. Smith (University of Oxford) , Benjamin M. Gallant (University of Oxford) , Suer Zhou (University of Oxford) , Robert J. E. Westbrook (University of Washington) , Yangwei Shi (University of Washington) , Jian Wang (University of Washington) , James N. Drysdale (University of Oxford) , Declan P. Mccarthy (University of Colorado Boulder) , Stephen Barlow (University of Colorado Boulder) , Seth R. Marder (University of Colorado Boulder) , Henry J. Snaith (University of Oxford) , David S. Ginger (University of Washington)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Energy Letters

State: Published (Approved)
Published: November 2022
Diamond Proposal Number(s): 30612

Abstract: We show that adding ethylenediamine (EDA) to perovskite precursor solutions improves the photovoltaic device performance and material stability of high-bromide-content, methylammonium-free, formamidinium cesium lead halide perovskites FA1–xCsxPb(I1–yBry)3, which are currently of interest for perovskite-on-Si tandem solar cells. Using spectroscopy and hyperspectral microscopy, we show that the additive improves film homogeneity and suppresses the phase instability that is ubiquitous in high-Br perovskite formulations, producing films that remain stable for over 100 days in ambient conditions. With the addition of 1 mol % EDA, we demonstrate 1.69 eV-gap perovskite single-junction p-i-n devices with a VOC of 1.22 V and a champion maximum-power-point-tracked power conversion efficiency of 18.8%, comparable to the best reported methylammonium-free perovskites. Using nuclear magnetic resonance (NMR) spectroscopy and X-ray diffraction techniques, we show that EDA reacts with FA+ in solution, rapidly and quantitatively forming imidazolinium cations. It is the presence of imidazolinium during crystallization which drives the improved perovskite thin-film properties.

Diamond Keywords: Photovoltaics; Semiconductors

Subject Areas: Materials, Chemistry, Energy


Instruments: I07-Surface & interface diffraction

Added On: 02/11/2022 17:28

Discipline Tags:

Surfaces Earth Sciences & Environment Sustainable Energy Systems Energy Physics Climate Change Physical Chemistry Chemistry Materials Science interfaces and thin films Perovskites Metallurgy

Technical Tags:

Scattering Wide Angle X-ray Scattering (WAXS) Grazing Incidence Wide Angle Scattering (GIWAXS)