Public Abstract

DE-SC0014334: Shining light on hybrid perovskite intrinsic anion and cation instabilities

Award Status: Active

Institution: University of Notre Dame du Lac, Notre Dame, IN
UEI: FPU6XGFXMBE9
PM: Mewes, Tim

Most Recent Award Date: 08/06/2026
Number of Support Periods: 11
PI: Kuno, Masaru

Current Budget Period: 08/15/2025 - 08/14/2026
Current Project Period: 08/15/2024 - 08/14/2027

Public Abstract

Hybrid perovskites such as MAPbI3 (MA=CH3NH3+) and mixed-cation/mixed-anion counterparts such as (MA,FA,Cs)Pb(I1-xBrx)3 [FA=(NH2)2CH+] represent a potential paradigm shift for creating low-cost solar cells. Attesting to this, mixed-cation/mixed-anion devices now exhibit power conversion efficiencies that exceed those of silicon photovoltaics. Unfortunately, long-term stability issues impede their commercialization. Central are intrinsic hybrid perovskites instabilities that stem from light-induced anion photosegregation and bias-induced cation migration. Although great effort has been invested in addressing either phenomenon, many unknowns remain. This prevents rational approaches from being developed to ameliorate or eliminate their effects. In this renewal proposal, we conduct focused studies of anion and cation instabilities in hybrid perovskites. Two main topics are proposed. Topic 1 focuses on understanding anion dynamics in the limit of high excitation intensities. Here, it has been reported that an unusual photoremixing phenomenon exists where simply increasing light intensities reverses anion photosegregation. This is counterintuitive. If light induces photosegregation in the first place, why does adding more light reverse the phenomenon? More fundamentally, high light intensity anion photoremixing is not immediately predicted by any existing phenomenological model of perovskite anion instabilities. As such, its origin remains an open, basic science question. Topic 2 addresses recent use of two-dimensional (2D) Ruddlesden-Popper perovskite surface layers to stabilize and passivate bulk, three-dimensional (3D) perovskites that are employed as active layers in perovskite solar cells. Although 2D passivation reportedly improves device stabilities, more recent studies suggest unstable 2D/3D interfaces that stem from cation migration under illumination, under thermal stress, or even during aging. Proposed studies therefore aim to establish critical parameters that dictate and potentially control the tendency of cations to migrate at perovskite interfaces. In whole, the proposed effort addresses critical stability issues that hinder the successful application of hybrid perovskite materials. From a fundamental standpoint, we expand on prior investigations we have conducted to establish a microscopic model for mixed-halide perovskite anion photosegregation. We further broaden the study to include studies of cation instabilities with the intent of developing a comprehensive and microscopic accounting of ionic instabilities in lead-based perovskites.

Hybrid perovskites such as MAPbI3 (MA=CH3NH3+) and mixed-cation/mixed-anion counterparts such as (MA,FA,Cs)Pb(I1-xBrx)3 [FA=(NH2)2CH+] represent a potential paradigm shift for creating low-cost solar cells. Attesting to this, mixed-cation/mixed-anion devices now exhibit power conversion efficiencies that exceed those of silicon photovoltaics.

Unfortunately, long-term stability issues impede their commercialization. Central are intrinsic hybrid perovskites instabilities that stem from light-induced anion photosegregation and bias-induced cation migration. Although great effort has been invested in addressing either phenomenon, many unknowns remain. This prevents rational approaches from being developed to ameliorate or eliminate their effects.

In this renewal proposal, we conduct focused studies of anion and cation instabilities in hybrid perovskites. Two main topics are proposed. Topic 1 focuses on understanding anion dynamics in the limit of high excitation intensities. Here, it has been reported that an unusual photoremixing phenomenon exists where simply increasing light intensities reverses anion photosegregation. This is counterintuitive. If light induces photosegregation in the first place, why does adding more light reverse the phenomenon? More fundamentally, high light intensity anion photoremixing is not immediately predicted by any existing phenomenological model of perovskite anion instabilities. As such, its origin remains an open, basic science question.

Topic 2 addresses recent use of two-dimensional (2D) Ruddlesden-Popper perovskite surface layers to stabilize and passivate bulk, three-dimensional (3D) perovskites that are employed as active layers in perovskite solar cells. Although 2D passivation reportedly improves device stabilities, more recent studies suggest unstable 2D/3D interfaces that stem from cation migration under illumination, under thermal stress, or even during aging. Proposed studies therefore aim to establish critical parameters that dictate and potentially control the tendency of cations to migrate at perovskite interfaces.

In whole, the proposed effort addresses critical stability issues that hinder the successful application of hybrid perovskite materials. From a fundamental standpoint, we expand on prior investigations we have conducted to establish a microscopic model for mixed-halide perovskite anion photosegregation. We further broaden the study to include studies of cation instabilities with the intent of developing a comprehensive and microscopic accounting of ionic instabilities in lead-based perovskites.