Fundamental Optical Characterization of CH3NH3PbBr3 Perovskite Synthesized via Furnace Method

Fundamental Optical Characterization of CH3NH3PbBr3 Perovskite Synthesized via Furnace Method Abstract:Lean films of CH₃NH₃PbBr₃ perovskite were prepared by using a simple one-step deposition method, followed by a controllable thermal treatment process for the study of their optical properties and stability under ambient conditions. Two thermal annealing processes were studied: One at a fixed temperature of 80 °C and one at a slow temperature slope from 80 °C to 120 °C. The UV-Vis absorbance measurements showed a strong absorbance in the visible wavelength range. A distinct peak was observed at 555 nm for the 80 °C annealed sample indicating a direct bandgap transition. In this sample, a distinct physical decay was observed over a two day timeframe, indicated by new peaks and loss of an absorption of greater than an order of magnitude. In contrast, the slowly heated sample had stronger absorption and fewer remnants of PbBr₂, showing a red shift of the maximum absorption peak to about 545 nm. Properties of the as-cast films suggest that the film's quality and crystallinity were very elevated. Stability tests of the film showed that the film could retain complete optical and fundamental quality for three days; quality loss could be noted on the fourth day. An analysis of the Tauc plot showed that both films showed adjustable properties, however, the continuously processed film had a slightly larger optical bandgap, indicating improved thermal stability and greater resistance to light induced degradation. Coincidently, photoluminescence (PL) measurements confirmed these observations: A large shift within the emission wavelength from 557 nm to 645 nm wavelength from 557 nm to 645 nm- was observed over time, particularly in the less stable film verifying ongoing degradation. These results suggest that processing conditions will significantly influence the optoelectronic properties and overall stability of CH₃NH₃PbBr₃ perovskite solar films, providing helpful information for developing better devices. Keywords: Perovskite, optical properties, physical properties, photoluminescence, band gap.