Influence of the composition of hybrid perovskites on their performance in solar cells

During the last 5 years, power conversion efficiencies of hybrid (organic-inorganic) halide perovskite solar cells have shown impressive advances. This success has been partly due to the advances in thin film deposition techniques, but also due to the understanding of the chemical and structural characteristics of the hybrid organic-inorganic perovskites that make it possible to modulate their optoelectronic properties. Moreover, engineering the chemical composition of these materials still remains a powerful tool for further improvement of the photovoltaic activity of these materials. The preparation of efficient lead-free hybrid perovskites exhibiting reduced toxicity is one of the main targets. Besides environmental issues, the control of the composition of hybrid perovskites should be used to achieve a decrease in the bandgap energy, trying to extend the photoresponse of the materials into the NIR region. A third target is the long-term stability of devices, a property closely related to the negative influence of humidity and phase transition. This review focuses on showing how the modification of the composition of each of the three components (organic cation, metal and inorganic anion) of the parent hybrid halide perovskite (CH3NH3PbI3) influences the optoelectronic properties, photovoltaic efficiency and stability of these striking materials.