A Gradient Heterostructure Based on Tolerance Factor in High‐Performance Perovskite Solar Cells with 0.84 Fill Factor

Abstract

A gradient heterosturcture is one of the basic methods to control the charge flow in perovskite solar cells (PSCs). However, a classical route for gradient heterosturctures is based on the diffusion technique, in which the guest ions gradually diffuse into the films from a concentrated source of dopants. The gradient heterosturcture is only accessible to the top side, and may be time consuming and costly. Here, the “intolerant” n‐type heteroatoms (Sb3+, In3+) with mismatched cation sizes and charge states can spontaneously enrich two sides of perovskite thin films. The dopants at specific sides can be extracted by a typical hole‐transport layer. Theoretical calculations and experimental observations both indicate that the optimized charge management can be attributed to the tailored band structure and interfacial electronic hybridization, which promote charge separation and collection. The strategy enables the fabrication of PSCs with a spontaneous graded heterojunction showing high efficiency. A champion device based on Sb3+ doped film shows a stabilized power‐conversion efficiency of 21.04% with a high fill factor of 0.84 and small hysteresis.

Organic N‐Type Molecule: Managing the Electronic States of Bulk Perovskite for High‐Performance Photovoltaics

“…This leads to an increase in the interfacial charge collection efficiency, which is benefit in increasing J sc of pero‐SCs. [ 27 ]…”

“…[ 22–23 ] The electronic states can also be regulated through partial substitution of Pb by heterovalent Bi or Sb, thereby inducing shallow donor levels with small ionization energies in the bandgap and enhancing the electron density of states. [ 24–27 ] However, doping with metal ions is detrimental to the device stability due to the more severe ion migration (than that occurring in the nondoped material) particularly under operating conditions. [ 28–29 ] Recently, organic n‐type dopants of ETL have attracted considerable attention due to their easily tailored structure, [ 30–31 ] good solubility, [ 32 ] and remarkable stability without ion/atom migration.…”

Secondary Ion Mass Spectrometry (SIMS) for Chemical Characterization of Metal Halide Perovskites

“…Reproduced with permission. [75] Copyright 2019, Wiley-VCH. d-f) ToF-SIMS depth profiles of samples with the structure and interface location indicated in the bar shown above the plots.…”

Ultrathin Hematite Photoanode with Gradient Ti Doping

“…Time-of-flight secondary ion mass spectrometry (ToF-SIMS) with high surface sensitivity is always used for unravelling the spatial distribution of chemical components [22]. In this work, we carried out the ToF-SIMS characterizations to identify the gradient Ti doping.…”

“…Gradient doping is an efficient strategy of facilitating the charge transfer due to the resulting built-in electric field and has been thoroughly investigated in many fields, including photocatalysis, photovoltaics, and PEC water splitting [21][22][23][24][25]. For example, Abdi and coworkers developed gradient W-doped BiVO 4 photoanodes via the layer-by-layer spray pyrolysis method, consisting of 10-step different gradient W concentration, which ultimately facilitated the efficiency of photogenerated carriers because of the built-in electric field [23].…”