Customized succinic acid derived molecular structure to achieve 25.41% efficient and stable perovskite solar cells

• Minimizing interface charge defects in perovskite films is crucial for reducing non radiative recombination and improving device performance. In view of this, Wu Yihui and Peng Qiang from Sichuan University designed a series of succinic acid derivatives with different active sites and spatial configurations to regulate defects and crystallization in perovskite films.

  
  

  The succinic acid derivative dibromosuccinic acid (DBSA) with two symmetric Br atoms exhibits the optimal spatial arrangement for defect passivation. The experimental and theoretical results indicate that the carboxyl and atomic Br in DBSA have a synergistic effect with the undercoordinated Pb2+. In addition, strong electronegativity of Br effectively stabilizes the formamidine cation through electrostatic interactions.

  
  

  The final film quality is significantly improved, non radiative recombination is significantly reduced, and the photoluminescence lifetime exceeds 4 μ s. Carrier diffusion length reaches 3 μ M. Ultimately, an excellent efficiency of 25.41% (certified as 25.00%) was achieved, as well as a high fill factor of 84.39% and excellent long-term operational stability.

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• Figure 1. DFT calculation on the functional molecules and defective perovskites.(a)Molecular structures and electrostatic potentials (ESP) of the SA-derivative.(b)Simplifiedtop-viewed atomic structures of various types of surface charged defects in perovskites. (c)Defect formation energy for the typical charged defects in perovskites. (d) The adsorptionenergy between SA-derivative and the iodine vacancy in perovskites.
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• Figure 2.(a)Partial enlarged FT-IR spectra of DBSA, DBSA-Pbg and DBSA-FAI films.(b)Liquid-state 'H nuclear magnetic resonance (NMR) spectra of DBSA，DBSA-PbI andDBSA-FAI (solvent: DMSO-d6).(c)Uv-Vis absorption spectra of DBSA, Pb, and DBSA-PbIp(solvent: DMSO). (d)UV-Vis absorption spectra of DBSA,FAI and DBSA-FAI(solvent: DMSO).High resolution XPS spectra of (e) Pb 4f and (f) I 3d for the perovskitefilms with different SA-derivative treatment.
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• Figure 3. Top-viewed SEM images of the (a) control, (b)SA-,(c)BSA-, and (d) DBSA-treated perovskite films. The cross-sectional SEM images of the devices based on the(e)control,(f) SA-,(g)BSA-, and (h) DBSA-treated perovskite films. AFM images of the (i)control, (j) SA-,(k)BSA-, and (1) DBSA-treated perovskite films.
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• Figure 4.(a)UV-Vis absorption spectra of the perovskite films with different SA-derivativetreatment (inset: the urbach energy for the corresponding perovskite films).(b) PL and (c)TRPL spectra of the perovskite films without and with the SA-derivative treatment. (d)Carrier diffusion length for the perovskite films with SA-derivative treatment. (e)Dark I-Vcurves of the electron-only devices based on the control and SA-derivative treatedperovskite films (FTO/SnOz/Perovskite/PCoBM/BCP/Ag).
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• Figure 5. (a) Schematic illustration of the device structure and the correspondingenergy levels.(b) Statistics of the PV parameters for 60 individual devices based ondifferent SA-derivative treatment.(c)J-V curves of the champion devices based on thecontrol and DBSA-treated perovskite films.(d) EQE curves and the correspondingintegrated photocurrent densities of the control and DBSA-treated devices. (e)Stabilized output efficiency of the device based on the DBSA-treated perovskitearound the maximum output power point as a function of time under simulated 1 sunillumination.
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• Figure 6.(a)Voc vs. light intensity of the devices without and with SA-derivativetreatment.(b)Mott-Schottky fitting to the capacitance-voltage (C.-V) plots of thedevices without and with SA-devirvative treatment. (c) Long-term stability of theunsealed devices based on the control and DBSA-treated perovskite stored at dark in aNz-filled glovebox. (d) Dynamic MPP tracking of the unsealed control and DBSA-

  
  

• Wang, Q., Chen, Y., Chen, X., Tang, W., Qiu, W., Xu, X., Wu, Y., Peng, Q., Tailored Succinic Acid-Derived Molecular Structures Toward 25.41%-Efficiency and Stable Perovskite Solar Cells. Adv. Mater. 2023, 2307709. 

  https://doi.org/10.1002/adma.202307709

  https://onlinelibrary.wiley.com/doi/10.1002/adma.202307709