Developing Hole Selective Layers and Implementing Large-size Organic Cations for Perovskite Solar Cells

Resumen

Thesis Abstract Organic-inorganic halide perovskite solar cells(PSCs) have emerged as one of the best candidates in nextgenerationphotovoltaics since their introduction in 2009. Thepower conversion efficiency (PCE) has dramatically increased from3.8% to 25.7% in a decade. However, due to their limited devicestability, the path to commercialization has been hindered, despiteexcellent PCEs. The highest performing PSCs is composed of severallayers such as electron transport layers, an n-type mesoporous TiO2layer, a perovskite layer, a hole transporting layer and a metalelectrode. The high PCE can be achieved by effectively extracting andcollecting the photogenerated holes and selectively reducing thecharge recombination loss. The state-of-art Spiro-OMeTAD is themost commonly used hole transporting material in the literature,however, its high cost due to multistep synthesis process, complexpurification and instability caused by adding of hygroscopic p-typedopants, hinders the large-scale industrialization of PSCs. Thus, thedevelopment of new designed HTMs is highly desired.Additionally, the dimensionality of the perovskite influences theperformance and stability of the PSCs. The reduction ofdimensionality to produce lower-dimensional perovskites or analternative approach to implement an interfacial layer of the leastamount of large organic cation to 3D perovskite surface to formbilayer or layered/3D mixed dimensional perovskites greatlyenhance the photovoltaic performance and stability of PSCs.Thus, the studies in this thesis aim to develop new hole-transportingmaterials that would be inexpensive and easily synthesizable andcan be effectively implemented for PSC applications. A series ofHTMs based on small molecules were designed and synthesized andinvestigated to understand the behaviour as a charge selective layerin PSCs, to further reduce the cost and improve the stability.Furthermore, the thesis discusses the work on the dimensionality ofthe perovskite and interface engineering of the perovskite absorberlayer with large organic cations for improved performance and longtermstability purposes.Thus, the thesis aims to discuss the studies and investigations on themolecularly designed hole-transporting materials (HTMs) andemploy the large-size organic cation as an interface layer or dopingto form reduced mixed-dimensional perovskite absorber forenhancing the overall performance and long-term stability of thePSCs.