Organic-inorganic lead halide perovskite solar cells (PSCs) have generated considerable interest in recent years because of their high-power conversion efficiency. However, while converting solar light to electrical power has reported efficiencies exceeding 20 %, operational stability remains a concern, and therefore is preventing the widespread application of these devices. Several previously conducted studies have reported that perovskite solar cells such as those based on methyl ammonium

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... iodide perovskite (CH3NH3PbI3 or MAPbI3) degrade rapidly when being operated under ambient operating conditions (e.g. in the presence of moisture and oxygen). The exact reason for the relatively poor stability of perovskite solar cells has yet to be fully elucidated. To better understand the reasons behind the poor stability and the rapid degradation of the PSCs in presence of moisture and oxygen, a new in-depth study was made and is the key focus of this thesis. Oxygen and light induced degradation has recently been shown to be an important pathway for CH3NH3PbI3 perovskite films. This oxygen-light degradation process involves the generation of highly energetic electrons while the films are exposed to both visible light and oxygen. These charges can then react with oxygen in the atmosphere generating a reactive oxygen species (superoxide, O2-) which reacts with the methyl ammonium cation and causes CH3NH3+ to deprotonate. The degradation and O2- generation process is monitored from comparing Ultraviolet Visible Light Spectroscopy (UV-vis), Photoluminescence (PL) and Transient Absorption Spectroscopy (TAS) measurements with the exposure time. The results concluded from these three set of experiments indicate two main findings: 1.) oxygen induced degradation is an important loss pathway for both films and fully functioning devices and 2.) the drop rate in the yield of charge transfer at metal oxide / CH3NH3PbI3 / hole transporting material HTM heterojunctions was found to be less when the MAPbI3 was deposited on an electro [...]