ntrinsic doping limitations in inorganic lead halide perovskite

Author(s)

Sabino, Fernando P. ^[1] ; Zunger, Alex ^[2] ; Dalpian, Gustavo M. ^[1]

Affiliation

^[1] Univ Fed ABC, Ctr Ciencias Nat & Humanas, BR-09210580 Santo Andre, SP - Brazil

^[2] Univ Colorado, Renewable & Sustainable Energy Inst, Boulder, CO 80309 - USA

• Document type: Journal article
• Source: MATERIALS HORIZONS; v. 9, n. 2 DEC 2021.
• Web of Science Citations: 0

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. In this paper 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-pin((n)) and holes E-pin((p)) (being the limiting value of the Fermi level 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 Delta E-F((n)) towards the conduction band for n-type doping (shift of Delta E-F((p)) 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. (AU)

• FAPESP's process: 17/02317-2 - Interfaces in materials: electronic, magnetic, structural and transport properties
• Grantee: Adalberto Fazzio
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 19/21656-8 - Big Data methods to tune perovskites to target properties: alloys, defects and doping
• Grantee: Fernando Pereira Sabino
• Support Opportunities: Scholarships in Brazil - Post-Doctoral