Optimization Of CsPbI₃ And CsPbIBr₂ Perovskite Solar Cell Performance Under Low-temperature Annealing By Engineering Interfacial Modifications Containing Butyl Molecules

The rapid improvement of the photoelectric conversion efficiency organic-inorganic hybrid perovskite solar cells（PSCs）is the result of more than ten years’hard work by a large number of experimenters.From 2009,when single-junction halide perovskite solar cells debuted with a mere 3.8%photoelectric conversion efficiency（PCE）,to 2022,many researchers and their groups have published a large number of articles with photoelectric conversion efficiencies exceeding 25%under years of dedicated research,and up to now,the highest certified efficiency record reported by NREL has reached 25.7%,which is gradually approaching the highest photovoltaic conversion efficiency of silicon-based solar cells.Perovskite solar cells have started to enter commercialization in the last two years,but the long-term stability of organic components in organic-inorganic hybrid perovskite solar cells under humid heat conditions can be seen due to the long-term stability of organic components in the crystal structure,which generally leads to poor overall stability of the device.It is thus a highly efficient means of using Cs⁺replace the cation therein to enhance the thermal stability of perovskite photovoltaic devices.Different types of interfacially modified substances were chosen to improve the performance of CsPbI₃and CsPbIBr₂perovskite films and their devices,as follows:（1）In this chapter,because of the large energy loss between functional layer interfaces,leading to poor device efficiency,we introduce a ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate（BMIMBF₄）interface modification of TiO₂dense layer.The good electron transport performance of the ionic liquid and the promotion of grain growth of CsPbIBr₂perovskite film are used to greatly improve the device performance precisely because the ionic liquid has a dual effect on the TiO₂dense layer and the CsPbIBr₂perovskite film.We obtained an optimal efficiency device with a PCE of 8.13%when using BMIMBF₄at a concentration of 1 mg/mL for interfacial modification.This efficiency is nearly 30%higher than the original PCE without interface modification.（2）In this chapter,tetrabutylammonium chloride（TBAC）is used as the top interface modification of CsPbI₃perovskite films.Since TBA⁺cations have strong exfoliation properties,TBAC can be used as a repair intercalation of perovskite to form a CsPbI=3perovskite film.One-dimensional TBAPbI₃structure increase the crystal size to improve the photoelectric conversion efficiency of the device,the one-dimensional TBAPbI₃structure not only has good thermal stability,but also has excellent humidity stability,which can be used as a barrier to prevent moisture and oxygen from entering the perovskite and improve the moisture stability of CsPbI₃perovskite.In this section,it is explored that the one-dimensional perovskite structure grown by TBAC has good stability at high humidity and temperature,which is effective in enhancing the stability of perovskite films and devices.After the optimization of TBAC,the devices achieved a PCE of 12.27%and maintained an initial efficiency of 86.8%with better hygrothermal stability even after 300 h of placement.（3）All-inorganic CsPbI₃perovskite solar cells have a higher perovskite phase transition temperature compared to the common organic-inorganic hybrid perovskite,which is why all-inorganic CsPbI₃perovskite solar cells have good thermal stability.However,there is a gap between the CsPbI₃perovskite film and the electron transport layer interface larger energy loss,and there are more non-radiative recombination centers at the same time,so the energy loss between the interfaces can be reduced by adjusting the energy level to improve the efficiency of perovskite photovoltaic devices.In this chapter,three halogenated ammonium salts tetrabutylammonium iodide（TBAI）,tetrabutylammonium chloride（TBAC）and tetrabutylammonium bromide（TBAB）are selected as the interface modification layer between the perovskite and electron transport layer,which not only can improve the conductivity of the electron transport layer SnO₂,but also lead to different interactions of the tetrabutylammonium cations due to the different halogen ions,resulting in the perovskite film also exhibit different crystalline properties,in addition to reducing the energy loss between the interfaces.Through the interfacial modification,not only a good efficiency of 12.85%was obtained in the all-inorganic carbon electrode based planar structure device without hole transport layer,but also the stability of the cell was significantly improved by maintaining72.7%of the most initial device efficiency after 150 h of sitting without encapsulation.