Fabrication and characterization of lead halide with the addition of caesium cation in Perovskite solar cells

Abstract

In general, Perovskite solar cells (PSCs) have been easily degraded by moisture, high temperature, etc. Additional of inorganic cation, e.g. Cs⁺ has been introduced to explore more complex compositions which also enhances the device performance and stability. In this work, PSCs with mixed organic-inorganic cations - MA₁-xCsxPb(I₁-yBry) ₃, where MA is methy1-ammonium, are fabricated by using the two-step spin-coating process. The halide group is also a mixture of iodide and bromide for bandgap energy tuning. The PSCs of n-i-p type are based on FTO/cp-TiO₂/mp-TiO₂/Perovskite/Spiro-OMeTAD/Au architecture. The amount of Cs is varied with x=0.03, 0.05, 0.07 and 0.09, while the amount of Br is varied with y = 0.05, 0.10, 0.15 and 0.20. Morphologies of the perovskite layers are investigated under the variations of Cs and Br. The open-circuit voltage (Voc) is directly affected by the addition of Br. The best PSC obtained in this work has Voc = 1.04 V, Jsc = 23.4 mA/cm², fill-factor = 64.7% and power conversion efficiency = 15.7%.