Orientation Manipulation and Defect Passivation for Perovskite Solar Cells by a Natural Compound.

Different facets in perovskite crystals exhibit distinct atomic arrangements, influencing their electronic, physical, and chemical properties. Perovskite films incorporating tin oxide (SnO2) as the electron transport layer face challenges in facet regulation. This study reveals that tea saponin (TS), a natural compound serves as a SnO2 modifier, facilitates optimal growth of perovskite crystals on the (111) facet. The modification promotes preferential crystal orientation through hydrogen bond and Lewis coordination. TS forms a chelate with SnO2, resulting in a smoother film and n-type doping, leading to improved carrier extraction and reduced defects. The TS-modified perovskite solar cells achieve a champion efficiency of 24.2%, leveraging from an obvious enhancement of open-circuit voltage (Voc) of 1.18 V and fill factor (FF) of 82.8%. The devices also demonstrate enhanced humidity tolerance and storage stability, ensuring improved stability without encapsulation.

Oxidation of Spiro-OMeTAD in High-Efficiency Perovskite Solar Cells.

2,2',7,7'-Tetrakis(N,N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD), as an organic small molecule material, is the most commonly employed hole transport material (HTM) in perovskite solar cells (PSCs) because of its excellent properties that result in high photovoltaic performances. However, the material still suffers from low conductivity, leading to the necessary use of dopants and oxidative processes to overcome this issue. The spiro-OMeTAD oxidation process is highlighted in this review, and the main parameters involved in the process have been studied. Furthermore, the best alternatives aiming to improve the spiro-OMeTAD electrical properties have been discussed. Lastly, this review concludes with suggestions and outlooks for further research directions.

Role of Ions in Hydrogels with an Ionic Seebeck Coefficient of 52.9 mV K-1.

Ionic thermoelectric (i-TE) material with mobile ions as charge carriers has the potential to generate large thermal voltages at low operating temperatures. This study highlights the role of ions in i-TE hydrogels employing a poly(vinyl alcohol) (PVA) polymer matrix and a number of ion providers, e.g., KOH, KNO3, KCl, KBr, NaI, KI, and CsI. The relationship between the intrinsic physical parameters of the ion and the thermoelectric performance is established, indicating the ability to influence the hydrogen bond by the ion is a crucial factor. Among these i-TE hydrogels, the PVA/CsI hydrogel exhibits the largest ionic Seebeck coefficient, reaching 52.9 mV K-1, which is the largest of all i-TE materials reported to date. In addition, our work demonstrates the influence of ions on polymer configuration and provides an avenue for ion selection in the Soret effect in ionic thermoelectrics.