Title: Intrinsic doping limitations in inorganic lead halide perovskites

Abstract

Inorganic halide perovskites (HP's) of the CsPbX₃ (X = I, Br, Cl) type have reached prominence in photovoltaic solar cell efficiencies, leading to the expectation that they are a new class of semiconductors relative to the traditional ones. Peculiarly, they have shown an asymmetry in their ability to be doped by holes vs. electrons. Indeed, both structural defect-induced doping as well as extrinsic impurity-induced doping strangely often result in HP's in a unipolar doping (dominantly p-type) with low free carriers’ concentration. This raises the question whether such doping limitations presents just a temporary setback due to insufficient optimization of the doping process, or perhaps this represents an intrinsic, physically-mandated bottleneck. Here we study three fundamental Design Principles (DP's) for ideal doping, applying them via density functional doping theory to these HP's, thus identifying the violated DP that explains the doping limitations and asymmetry in these HP's. Here, the target DP are: (i) requires that the thermodynamic transition level between different charge states induced by the dopants must ideally be energetically shallow both for donors (n-type) or acceptors (p-type); DP-(ii) requires that the ‘Fermi level pinning energies’ for electrons E⁽ⁿ⁾_pin and holes E^(p)_pin (being the limiting value of the Fermi levelmore » before a structural defect that compensate the doping forms spontaneously) should ideally be located inside the conduction band for n-type doping and inside the valence band for p-type doping. DP-(iii) requires that the doping-induced shift in equilibrium Fermi energy ΔE⁽ⁿ⁾_F towards the conduction band for n-type doping (shift of ΔE^(p)_F towards the valence band, for p-type doping) to be sufficiently large. We find that, even though in HP's based on Br and Cl there are numerous shallow level dopants that satisfy DP-(i), in contrast DP-(ii) is satisfied only for holes and DP-(iii) fails for both holes and electrons, being the ultimate bottleneck for the n-type doping in Iodide HP's. This suggests an intrinsic mechanism for doping limitations in this class of semiconductors in terms of recognized physical mechanisms.« less

Authors:

Sabino, Fernando P.  ^[1];

• Search DOE PAGES for author "Sabino, Fernando P."
• Search DOE PAGES for ORCID "0000-0002-5296-0017"

Zunger, Alex  ^[2];

• Search DOE PAGES for author "Zunger, Alex"
• Search DOE PAGES for ORCID "0000-0001-5525-3003"

Dalpian, Gustavo M.  ^[1]

• Search DOE PAGES for author "Dalpian, Gustavo M."
• Search DOE PAGES for ORCID "0000-0001-5561-354X"

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+ Show Author Affiliations

1. Universidade Federal do ABC, Sao Paulo (Brazil)
2. University of Colorado, Boulder, CO (United States)

Publication Date:

Thu Dec 02 00:00:00 EST 2021

Research Org.:

Univ. of Colorado, Boulder, CO (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE); Support Foundation to São Paulo State Research (FAPESP); National Council for Scientific and Technological Development (CNPq); Coordination for the Improvement of Higher Education Personnel (CAPES); USDOE

OSTI Identifier:

1978805

Alternate Identifier(s):

OSTI ID: 1835650

Grant/Contract Number:  

SC0010467; 2019/21656-8; 17/02317-2

Resource Type:

Accepted Manuscript

Journal Name:

Materials Horizons

Additional Journal Information:

Journal Volume: 9; Journal Issue: 2; Journal ID: ISSN 2051-6347

Publisher:

Royal Society of Chemistry

Country of Publication:

United States

Language:

English

Subject:

36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Halide perovskites; doping; defects; self-regulating mechanism; Fermi level pinning