Robust Interfacial Modifier for Efficient Perovskite Solar Cells: Reconstruction of Energy Alignment at Buried Interface by Self‐Diffusion of Dopants

Abstract

The under-coordinated defects within perovskite and its relevant interfaces always attract and trap the free carriers via the electrostatic force, significantly limiting the charge extraction efficiency and the intrinsic stability of perovskite solar cells (PSCs). Herein, self-diffusion interfacial doping by using ionic potassium L-aspartate (PL-A) is first reported to restrain the carrier trap induced recombination via the reconstruction of energy level structure at SnO 2 /perovskite interface in conventional n-i-p structured PSCs. Experiments and theories are consistent with the PL-A anions that can remain at the SnO 2 surface due to strong chemical adsorption. During the spin-coating of the perovskite film, the cations gradually diffuse into perovskite and endow an n-doping effect, which provides higher force and a better energy level alignment for the carrier transport. As a result, they obtained 23.74% power conversion efficiency for the PL-A modified small-area devices, with dramatically improved open-circuit voltage of 1.19 V. The corresponding large-area devices (1.05 cm 2 ) achieved an efficiency of 22.23%. Furthermore, the modified devices exhibited negligible hysteresis and enhanced ambient air stability exceeding 1500 h.

Multifunctional anthraquinone-sulfonic potassium salts passivate the buried interface for efficient and stable planar perovskite solar cells

“…2b). 36 Moreover, the O 1s spectra in both SnO 2 films can be deconvoluted into lattice oxygen (O 2− ) and chemisorbed hydroxyl groups (OH − ). 42 For the ASPS-modified SnO 2 films, the ratio intensity of oxygen in hydroxyl groups on the SnO 2 surface is significantly reduced, which indicates that the chemical environment of oxygen atoms in the SnO 2 surface lattice has changed after the ASPS treatment.…”

“…For example, K + ions can spontaneously diffuse into the upper PVK film to inhibit nonradiative recombination originating from boundary trap defects. 30,36 Meanwhile, the -SO 3 2À and -CQO groups located at the ends of ASPS can reinforce the chemical bridging between the ETL and the upper PVK by chelating with uncoordinated Sn 4+ and Pb 2+ ions. [37][38][39] On the other hand, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of ASPS are À5.80 eV and À2.22 eV, respectively.…”

“…42 For the ASPS-modified SnO 2 films, the ratio intensity of oxygen in hydroxyl groups on the SnO 2 surface is significantly reduced, which indicates that the chemical environment of oxygen atoms in the SnO 2 surface lattice has changed after the ASPS treatment. 34,36 The reduced concentration of hydroxyl groups on the SnO 2 surface can greatly depress the surface defect states and suppress non-radiative recombination, thus improving the carrier transport properties at the buried interface. 45 To further explore the influence of ASPS treatment on the energy level arrangement of SnO 2 film, ultraviolet photoelectron spectroscopy (UPS) was carried out, as shown in Fig.…”

Buried interface passivation strategies for high-performance perovskite solar cells

“…101 The corresponding device depicts promoted stability, showing only a 15% PCE decline even aer storage at 25% relative humidity for 1000 hours. Wang et al adopted ionic potassium L-aspartate (PL-A) and reconstructed the energy alignment at SnO 2 /perovskite interface through the self-diffusion interface doping, 80 as exhibited in Fig. 8f.…”

Modulating Residual Lead Iodide via Functionalized Buried Interface for Efficient and Stable Perovskite Solar Cells

“…When the film was overlaid on SnO 2 , the PL intensity decreased due to the electron extraction to the ETL (Figure a). Especially, the PL intensity showed a larger quenching on SnO 2 /DDSI 2 , indicating more efficient exciton extraction at the bottom interface. , The time-resolved photoluminescence (TRPL) spectra were fitted by a double-exponential decay function. The extended TRPL lifetime of the DDSI 2 perovskite suggests that DDSI 2 treatment can effectively passivate defects in perovskite films by improving crystal quality (Figure b and Table S1).…”