The performance of organic solar cells is determined by the delicate, meticulously optimized bulk-heterojunction microstructure, which consists of finely mixed and relatively separated donor/acceptor regions. Here we demonstrate an abnormal strong burn-in degradation in highly efficient polymer solar cells caused by spinodal demixing of the donor and acceptor phases, which dramatically reduces charge generation and can be attributed to the inherently low miscibility of both materials. Even though the microstructure can be kinetically tuned for achieving high-performance, the inherently low miscibility of donor and acceptor leads to spontaneous phase separation in the solid state, even at room temperature and in the dark. A theoretical calculation of the molecular parameters and construction of the spinodal phase diagrams highlight molecular incompatibilities between the donor and acceptor as a dominant mechanism for burn-in degradation, which is to date the major short-time loss reducing the performance and stability of organic solar cells.

A simulation of the optical properties of nanocomposite coatings derived from VO₂ nanoparticles (NPs) shows that the nanocomposite coatings have advantages over pure VO₂ thin films in their solar energy modification ability (ΔT_sol) and luminous transmittance (T_lum). These nanocoatings rely on fine quality VO₂ NPs; methods to prepare NPs for this purpose are yet to be developed. By studying the formation mechanism of VO₂ NPs, the NP preparation process was optimized, and fine crystal quality VO₂ NPs with diameters from 25–45 nm were synthesized. The highest latent heat of these VO₂ NPs is 43 J g⁻¹, which is considerably higher than the 25 J g⁻¹ reported previously and close to the 51 J g⁻¹ of bulk VO₂, which indicates that these VO₂ NPs are highly crystalline. These NPs showed an asymmetrical phase transition and increased insulator–metal transition (IMT) temperatures. According to our results, the size of particles is not the only reason that should be responsible for the increased IMT temperatures. The high-quality NPs were dispersed in polyurethane (PU) and coated on polyethylene terephthalate (PET). The relationship between the solar energy modification ability (ΔT_sol) and the luminous transmittance (T_lum) was studied by experiments and simulation. Although the best experimental values of ΔT_sol = 22.3% and T_lum = 45.6% are still lower than the simulation results of ΔT_sol = 23.7% and T_lum = 32.4%, these values represent the best for reported VO₂ smart films or coatings.

F-doped VO₂ (M1) nanoparticles were prepared via one-pot hydrothermal synthesis. The F-doping can minimise the size of the VO₂ (M1) nanoparticles, induce a homogeneous size distribution and effectively decrease the phase transition temperature to 35 °C at 2.93% F in VO₂. VO₂ smart glass foils obtained by casting these nanoparticles exhibit excellent thermochromism in the near-infrared region, which suggests that these foils can be used for energy-efficient glass. Compared to a pure VO₂ foil, the 2.93% F-doped VO₂ foil exhibits an increased solar-heat shielding ability (35.1%) and a modified comfortable colour, while still retaining an excellent solar modulation ability (10.7%) and an appropriate visible transmittance (48.7%). The F-doped VO₂ foils are the first to simultaneously meet the requirements of a reduced phase transition temperature, diluted colour and excellent thermochromic properties, and these properties make the further improved F-doped VO₂ foils suitable for commercial applications in energy efficient glass.

Photoinduced degradation mechanisms of CH₃NH₃PbI₃ thin films under vacuum and in air are reported.

As perovskite solar cells are highly efficient and already meet the efficiency requirement for renewable power generation, more attention is given to technological barriers such as scalability and stability. In particular, the large efficiency losses associated with upscaling lab-scale devices to large-area modules represents one of the major hurdles for commercialization. Given the essential role of the perovskite films in the device performance, it is of critical importance to develop reliable crystallization protocols to deposit high-quality perovskite layers via scalable methods. This review summarizes recent advances in emerging crystallization protocols for the large-scale deposition of perovskite thin films. The unique merits of the well-developed crystallization strategies, including antisolvent, gas quenching, vacuum quenching, etc., are carefully analyzed and discussed. We highlight that, independent of the coating method, creating intermediate phases to decouple the otherwise overlapped solution coating and crystal growth is essential to realize homogeneous coatings of perovskite thin films. Strategies for enhancing the crystal morphology of perovskite films are presented as well, which is vitally important to realize reproducible manufacturing of large-area modules. This tutorial review assists the screening and development of robust crystallization strategies for scalable deposition of high-quality perovskite films for photovoltaic applications.