All-inorganic halide perovskite nanocrystals (IPNCs), for example, CsPbX3 (X = Cl, Br, I), have potential as materials for optoelectronic devices. IPNCs are stable, exhibit luminescence that is tunable over the whole visible spectrum, and show high quantum yields. The materials can be used as thin films, however, solution-processed ﬁlms often have cracks and holes that hinder the efficient transport of charge carriers.
Haibo Zeng, Nanjing University of Science and Technology, China, and colleagues have developed a dissolution-recyrstallization process which can “heal” such cracks in perovskites at room temperature. The team first prepared CsPbBr3-nanocrystals by adding micrometer-sized CsPbBr3 particles to a mixture of toluene and the surfactants oleic acid and oleylamine. The mixture was then stirred for ten hours until a solubility equilibrium was reached. Thin films were prepared by soaking a substrate such as glass in a dispersion of the nanocrystals in toluene and centrifuging the substrate for 3 minutes.
To heal the defects in the prepared films, the film was covered with a ﬁlter paper and a mixture of toluene and ethanol was dropped on the ﬁlter and left to evaporate. This process was repeated multiple times. The solvent mixture dissolves sharp edges of the perovskite film, filles holes and cracks, and allows the perovskite to recrystallize upon evaporation. Toluene enhances the diffusion of the surfactant, while the more polar ethanol promotes the solvation of surface atoms.
The team built photodetectors (PDs) based on the treated perovskite ﬁlms. The devices showed high external quantum efﬁciencies, fast response speeds, and high stability, and overall performed better than most otherplanar perovskite PDs. According to the researchers, the film modiﬁcation method is suitable for all kinds of inorganic halide perovskite devices, especially for solution-processed ﬂexible devices.
- Healing All-Inorganic Perovskite Films via Recyclable Dissolution-Recyrstallization for Compact and Smooth Carrier Channels of Optoelectronic Devices with High Stability,
Xiaoming Li, Dejian Yu, Fei Cao, Yu Gu, Yi Wei, Ye Wu, Jizhong Song, Haibo Zeng,
Adv. Funct. Mater. 2016.