Defect Tolerance of Mixed B-Site Organic–Inorganic Halide Perovskites

Abstract

Further improvements in the photovoltaic performance of B-site alloyed organic−inorganic halide perovskites (OIHPs) will rely on accurate modeling of defect properties and passivation strategies. Herein, we report that B-site alloying results in defect behaviors distinct from those of pure OIHPs, a finding obtained by uniting first-principles calculations with experimental measurements. We identify from computational studies a defect-tolerant region spanning a Sn content of 30−70% in mixed Pb-Sn perovskites and experimentally observe notably longer carrier lifetimes in 50% Sn mixed perovskite films than at other Sn contents. We discuss a strategy of applying defect-tolerant 50% Pb-Sn perovskites in ideal-bandgap (1.3−1.4 eV) active layer materials which conventionally rely on 25−30% Sn compositions. The composition (FA 0.75 Cs 0.25 Pb 0.5 Sn 0.5 (I 0.9 Br 0.1 ) 3 ) achieves increased carrier lifetimes of >1 μs. This work reveals a general trend in defect tolerance for B-site alloying: a higher valence band maximum (lower conduction band minimum), along with strengthened ionic bonding, can potentially contribute to improved photovoltaic performance.

The high open-circuit voltage of perovskite solar cells: a review

“…5d). 51 Although all-inorganic perovskites are lagging a bit behind the hybrid perovskites in achieving high V OC with minimum E loss , a recent theoretical study revealed that the CsPbI 3 can be more defect-tolerant than MAPbI 3 . 52 The V OC loss in all-inorganic perovskites must be linked to the phase stability/impurity.…”

A Selective Targeting Anchor Strategy Affords Efficient and Stable Ideal‐Bandgap Perovskite Solar Cells

“…To be precise, more categories of defects, whether it is a Pb-or Sn-sourced, are forced to be placed in a deeper location, especially for acceptors such as A-site vacancies (V A ). [59] The interaction between PEAI and EDAI with perovskites could be categorized into two pathways: I) the iodide anions from anchor molecules fill the iodide vacancies (V I ) in the metal-halide octahedrals; [53] II) the bulky cations with different electrostatic potentials tend to selectively fill the A-site vacancies (V A ) with different charged situations, while contacting with the metal-halide octahedral through ionic bonds. [60,61] A range of characterization techniques was carried out to investigate the interaction between EDAI and PEAI molecules and perovskite, aiming to find out the mechanism of synergistic effect.…”

“…To be precise, more categories of defects, whether it is a Pb‐ or Sn‐sourced, are forced to be placed in a deeper location, especially for acceptors such as A‐site vacancies (V A ). [ 59 ]…”

Pressure response of decylammonium-containing 2D iodide perovskites

“…The red shift is then continuous until the maximum pressure investigated (11.4 GPa). With respect to DA 2 PbI 4 , the absorption edges are less defined and this is a feature quite common in lead-free perovskites with a possible origin in their reduced defect-tolerance ( Xu et al., 2021 ). The values of the absorption onset extracted from the Tauc plots (except for some points at low pressure where, given the broad nature of the transitions, we used the maximum absorbance approach) show a change of slope and a sudden decrease in correspondence of about 2 GPa, i.e., the pressure where the patterns were refined with two phases with space group P 2 1 / a and the c axes that differ by approximately 1 Å (see above the XRD section).…”