Organic Inorganic Heterojunctions for Application in Perovskite Based Photovoltaics

Abstract

Organic-inorganic lead halide perovskite solar cells (PSC s) research has seen most notable progress in the field of photovoltaics (PV). The very first PSC was reported in the year 2009 with efficiency of 3.8%, which rapidly increased to the record 25.2% in year 2020. These numbers are quickly approaching the record values achieved for single-crystal silicon based solar cells. Defect tolerant nature of perovskite, high carrier lifetime, ability to tune band-gap and low-cost solution-based processing in addition to many rare properties makes it an ideal candidate for future solar cell technology. These are the properties which also allows this material to find applications beyond PSC s, like photodetectors, memory, thin-film transistors (TFT s), etc. However, given the many valuable properties of this class of material, they also come with some dominating properties which hampers commercialization of this PV technology. Problems like, Ion-migration, degradation in ambient condition still have not fully solved and understood. This research field still have many unanswered questions like, finding suitable compositional engineered lattice to make system stable, role of interface on charge transport and device stability. In this work, we have developed a novel process to grow micron size grains of CH3NH3PbI3 (MAPI) using a custom-made glass reactor. Pristine films are spin-coated on substrate in a glove-box and transferred to methyl-amine gas filled reactor followed by annealing of the whole setup in controlled environment. The resulted films are conformal with average grain size of gt 1 microns. The resulted films are used to demonstrate the increase in minority carrier lifetime upon annealing in methyl-amine gas environment. Fabricated devices also showed improvement in device performance upon inclusion of large-grained MAPI film as compared to pristine MAPI film. At later stage, optimization of compact layer (c-TiO2) and mesoporous layer (m-TiO2) is performed followed by improved device fabrication methodology...