ACS Energy Lett, University of Electrical and Communications Synthesis of novel SAM for improving the efficiency of broadband gap perovskite and fully perovskite stacked solar cells

• Perovskite solar cells (PSC) have recently made progress due to their long carrier lifetime, tunable bandgap matching, and optical absorption. According to reports, the power conversion efficiency (PCE) of single junction PSC has reached 26.1%, which is equivalent to silicon solar cells (Si PSC). In pursuit of higher efficiency, perovskite series solar cells have attracted people's interest. All perovskite series solar cells are a type of perovskite series solar cells.

• All perovskite series solar cells are composed of narrow bandgap PSC (NBG PSC) and wide bandgap PSC (WBG PSC). Many works have been carried out to explore NBG PSC composed of Sn/Pb alloy calcium titanium ore layers, with reported efficiency of 23-24%. Improving the efficiency of WBG PSC is another important topic. Due to the bandgap of approximately 1.2 eV in Sn/Pb perovskite solar cells, the bandgap of the top PSC layer must be approximately 1.7-1.8 eV. We chose FA0.8Cs0.2PbI1.8Br1.2 as the top layer. As is well known, poly (bis (4-phenyl) (2,4,6-trimethylphenyl) amine) (PTAA) is a representative hole transport layer. However, due to its hydrophobicity, the surface of perovskite cannot be well contacted. Therefore, the quality of perovskite thin films often forms is relatively poor. Therefore, it is crucial to develop more suitable HTLs to further improve the quality of thin films and the performance of devices.

  
  

  
  

  Research progress

  Recently, Researchers from the National University of Electrical and Telecommunications in Japan (Bi Huan: ORCID: 0000-0001-7680-9816; Shuzi Hayase and Shen Qing: ORCID: 0000-0001-8359-3275), in collaboration with researchers from the University of Tokyo (Hiroshi Segawa: ORCID 0000-0001-8076-9722) and Kaunas Institute of Technology (Saulius Grigalevicius), published an article titled 'ACS Energy LETTERS' titled' The research article "All Perovskite Tandem Solar Cells Approach 26.5% Efficiency by Employing Wide Bandgap Lead Perovskite Solar Cells with New Monomolecular Hole Transport Layer" synthesized a novel self-assembled molecule (4dp3PACz) and demonstrated that the single-molecule layer of 4dp3PACz acts as a hole transport layer better than previously reported 2PACz and PTAA. Tests have shown that the calcium titanium layer prepared on 4dp3PACz has better quality, such as lower carrier trap density, longer carrier lifetime, and larger charge recombination resistance. This may be due to the hydrophilic properties and favorable band bending (energy level matching and band bending caused by Fermi level) of 4dp3PACz. At the same time, the -4dp functional group can also effectively passivate defects in the film. The photoelectric conversion efficiency of the final device reaches 17.17% (1.77 eV bandgap). In addition, a fully perovskite/perovskite series solar cell with an efficiency of 26.47% was also reported.

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• (a) The synthesis route of 4dp3PACz.

  (b) The device structure and molecular schematic diagram used in this work.
  

  (c) P 2p XPS signals (ITO, ITO/2PACz, and ITO/4dp3PACz) tested on different substrates.
  

  (d) Evaluation of defect density of perovskite thin films prepared on different substrates.
  

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• (a) The TPV curve of HTL devices using 2PACz or 4dp3PACz.

  (b) TRPL curves of perovskite thin films deposited on glass, ITO, ITO/2PACz, and ITO/4dp3PACz.
  

  (c) EIS testing of controller and target devices.
  

  (d) Evaluate the band bending of ITO/2PACz/PVK and (e) ITO/4dp3PACz/PVK.
  

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• (a) The forward and reverse scanning J-V curve characteristics of devices prepared using PTAA -, 2PACz -, and 4dp3PACz as hole transport layers.

  (b) IPCE testing of devices prepared with HTL using 2PACz and 4dp3PACz.

  (c) MPPT test results of devices with different HTLs.

  (d) Long term stability testing of devices with different HTLs.

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• (a) The structure of the fully perovskite series solar cell used in this work.

  (b) J-V curves and (c) IPCE curves of all perovskite stacked devices using 4dp3PACz as HTL.
  

  (d) Stability of the aged fully perovskite stacked PSC in an unpackaged series in a nitrogen filled glove box.
  

  
  

  
  

  Bi, H; Liu, J; Zhang, Z; Wang, L; Beresneviciute, R; Tavgeniene, D; Kapil, G; Ding, C; Et al. All Perovskite Tandem Solar Cells Approach 26.5% Efficiency by Employing Wide Bandgap Lead Perovskite Solar Cells with New Monoolecular Hole Transport Layer ACS energy letters 2023 DOI: 10.1021/acsenergylett. 3c01275
  

  
  

  Web: https://pubs.acs.org/doi/10.1021/acsenergylett.3c01275