Angew: Co-La based hole transport layer realizes binary organic solar cells with 18.82% efficiency

• Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a widely used hole transport layer (HTL) in organic solar cells (OSCs), but its acidity severely reduces device stability. So far, few HTLs have been developed to replace PEDOT:PSS as stable and high-performance OSCs. Recently, Weiwei Li and Qiaomei Chen of Beijing University of Chemical Technology have developed a simple and green method to obtain solution-processed cobalt-lanthanum (Co-La)-based inorganic HTLs for highly efficient OSCs.

• Co-La-based HTLs with different La contents (from 0% to 100% molar ratio) were simply prepared from isopropanol precursor solutions of cobalt nitrate (Co2+) and lanthanum nitrate hexahydrate (La3+), a small amount of peroxide Hydrogen (H2O2) and heat treatment at 80°C. La, an abundant and environmentally friendly rare-earth metal with an electron-rich outer shell structure, is widely used to dope semiconductor materials to improve their optoelectronic properties.

  
  

  It is found that H2O2 and La have a synergistic effect in improving the photovoltaic performance of related OSC devices. The OSC device based on HTL without La addition (i.e., Co-La0%) showed the best PCE of only 16.81%, while the performance was significantly improved with La addition. The champion-level PCE of 18.82% is achieved based on Co-La50% as an HTL device, the open circuit voltage (Voc) is 0.886 V, the short circuit current density (Jsc) is 26.64 mA cm-2, and the fill factor (FF) is 79.65% , much higher than the PEDOT:PSS-based device (18.03%). It is worth noting that this PCE ranks among the top among the current binary hybrid OSCs.

  
  

  Compared with PEDOT:PSS-based devices, Co-La50% based devices exhibit excellent long-term stability under different conditions, such as storage in a N2-filled glove box, ambient humidity, and continuous light. Moreover, when Co-La50% HTL was used in other commonly used non-fullerene systems, such as PM6:BTP-BO-4Cl and PM6:IT-4F, OSC devices also showed higher PCEs.

  
  

  The facile and low-cost process, excellent photovoltaic performance, and long-term stability of related OSC devices show the great application potential of Co-La-based high-temperature superconducting materials in high-performance OSCs.

• 
• 
• 

• Guangcong Zhang, et al, Co-La-Based Hole-Transporting Layers for Binary Organic Solar Cells with 18.82% Efficiency, Angew. Chem. Int. Ed. 2022, e202216304

  
  

  DOI: 10.1002/anie.202216304

  
  

  https://doi.org/10.1002/anie.202216304