Hole Transport Layer Optimization for a Triple Halide Perovskite Solar Cells using Poly-TPD

Triple halide perovskite solar cells have shown high efficiency and suppressing light induced halide segregation. However, optimizing the hole transport layer (HTL) is critical as it plays a pivotal role in perovskite solar cell efficiency by facilitating the efficient extraction and transport of charge carriers which can minimize energy losses, reduce recombination of charge carriers. In this work, solar cells were fabricated with the structure ITO/Poly-TPD/ Cs_0.22 FA_0.78 Pb (I_0.85 Br_0.15)₃ /C₆₀/BCP/Al. For initial experiments, 150 µl volume of 1 mg/ml concentration of Poly-TPD in chlorobenzene was deposited at 4000 RPM for 40s on glass ITO dynamically. The absorber layer was spun from DMF: DMSO (4:1 ratio) perovskite ink along with Methyl Acetate as an antisolvent. To further improve wettability with perovskite ink, a 150 µl volume of PFN-Br (0.5mg/ml in ethanol) was deposited on top of the HTL dynamically at 5000 RPM for 30s as a surfactant. Preliminary devices results indicate a power conversion efficiency (PCE) of 8.58%. To improve the PCE, we are currently optimizing film thickness and deposition parameters of the HTL material. Stylus profilometry and ellipsometry are used to determine the film thickness of the HTL layer. The latter is found difficult because of the small difference in optical density between the glass ITO substrate and the Poly-TPD.

This work was in part funded by the Department of Navy’s HBCU/MI Program through ONR grant number N00014-19-1-2576 and in part by NSF through grants 1906492.