No abstract

Cesium (Cs) contained triple-cation and mixed halide perovskite (CsFAMA) is broadly employed as light absorption layers for efficient and stable perovskite solar cells (PSCs) fabrication with high reproducibility. On the other hand, thermal annealing is a universal posttreatment method for perovskite films preparation. Moreover, thermal management highly depends on perovskite materials. However, no specialized study has been reported on CsFAMA perovskite to date. Herein, we have systematically investigated the influence of thermal annealing and annealing time on CsFAMA films and their solar cells. We demonstrated that heating time of 45 or 60 min at 100 °C is desirable. More interestingly, we found that the unannealed CsFAMA films exhibit ultrahigh photoluminescence (PL) intensities, much stronger than that of annealed films. Note that PL intensities gradually weaken as a function of annealing time. In particular, the PL intensities of fresh films (after antisolvent dripping) are at least 200 times higher than that of 60 min annealed films. To our knowledge, it is the first time to report this PL behavior. We speculate that it is due to quantum confinement effect of perovskite crystal nuclei and "cage effect" of DMSO intermediates in the fresh films. To this point, the unannealed CsFAMA films may have great potential in PL emission applications.

As-doped p-type ZnO films were grown on GaAs by sputtering and thermal diffusion process. Hall effect measurements showed that the as-grown films were of n-type conductivity and they were converted to p-type behavior after thermal annealing. Moreover, the hole concentration of As-doped p-type ZnO was very impressible to the oxygen ambient applied during the annealing process. In addition, the bonding state of As in the films was investigated by x-ray photoelectron spectroscopy. This study not only demonstrated an effective method for reliable and reproducible p-type ZnO fabrication but also helped to understand the doping mechanism of As-doped ZnO.

Post-treatment of perovskite films plays a crucial role in obtaining high-performance perovskite solar cells (PSCs). Solvent annealing (SA), as a universal post-treatment strategy, is profoundly beneficial for enhancing the quality of perovskite films. Here, a mixed-solvent vapor (MSA)-assisted gradient thermal annealing strategy is developed for the post-treatment of perovskite films. It is found that the synergistic effect of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is significant for obtaining high-quality perovskite films with large grain size and low trap state density, which shows much better effects in comparison with single-solvent annealing. MSA-treated planar PSCs with a regular n–i–p structure achieve a maximum power conversion efficiency (PCE) of 19.76% with an average PCE of 19.29% under a reverse scan at a rate of 0.1 V/s, compared with an average PCE of 15.85% of the counterparts (TTA) with thermal annealing only. Such facile, effective, and low-cost annealing strategy exhibits commendable utilization potentiality to obtain high-quality perovskite films and efficient PSCs.