Intensity Modulated Photovoltage and Photocurrent Spectroscopy Studies on Perovskite Solar Cells

Organometallic perovskite solar cells (PSCs) are a novice device that has got much attention due to the achievement of power conversion efficiency of about 22% shortly after its inception. The light absorbers primarily used in perovskite solar cells, methylammonium lead halides (CH₃NH₃PbX₃, where X is a halogen), have a structure like Calcium Titanium Oxide (CaTiO₃). A problem associated with these organometallic materials is their interaction with the environment causing stability problems to the devices. A critical understanding of the environmental impact on the structure and kinetic properties would help to improve the stability of the devices. We recently developed a setup for intensity modulated photovoltage/photocurrent spectroscopies (IMVS and IMPS respectively) to study the carrier transport properties in these solar cells. Instead of a frequency response analyzer often used in this technique, we employed a lock-in amplifier to modulate the intensity of a light source and measure the current/voltage response of the devices. In this presentation, we will discuss the instrumentation and the results of the carrier transport property studies performed on the orthorhombic, tetragonal and cubic phases of CH₃NH₃PbI₃ upon their exposure to different humidity conditions.