Morphology Analysis of Lead Iodide- and Lead Acetate-Based Perovskite Layers for Solar Cell Application
Thesis
Organolead trihalide perovskite solar cells have shown success as light absorbers in photovoltaic cells due to their efficiency increasing from 3.5% to over 20% within only five years. However, pinhole formation and incomplete coverage of solution-processed perovskite film results in increased current leakage, reducing efficiency. Hence the surface morphology of perovskite film is important for high performance of perovskite solar cells. Here the morphology is carefully controlled by varying processing conditions, perovskite films were prepared using two different lead sources: lead acetate (Pb(OAc) 2 ) and lead iodide (PbI 2 ), with methylammonium iodide (CH 3 NH 3 I) as the source material. The structural, optical and absorbance properties of the perovskite films varied with the lead sources used, perovskite from a Pb(OAc) 2 .3H 2 O source annealed at 90 o C gave the best structure compared to Pb(OAc) 2 .3H 2 O annealed at 80 o C and anhydrous Pb(OAc) 2 annealed at 90 o C. The perovskite film from the PbI 2 source did not have smooth film, pinholes were formed with low crystallinity, a small amount of Pb(OAc) 2 (about 5% mol) was added to the PbI 2 in the solution, this improved the film crystallinity. The perovskite film derived from lead acetate showed enhanced surface coverage with quality crystalline film.