SnO 2 is considered as a promising electron transport material for carbon-based perovskite solar cells (C-PSCs) due to its excellent electron mobility, stability over TiO 2 , and low-temperature processing. However, the lattice mismatch and poor contact quality of the SnO 2 /CH 3 NH 3 PbI 3 interface, as well as oxygen vacancies, usually lead to nonradiative recombination and limit the further improvement of photovoltaic performance. In this paper, two chitosan derivatives, chitosan quaternary ammonium salt (HACC) and carboxymethyl chitosan (CMCS), were used as additives for SnO 2 to adjust the energy level and improve the contact performance of the SnO 2 /CH 3 NH 3 PbI 3 interface. These two additives have suitable terminal active functional groups, amino group and hydroxyl group, which can interact with SnO 2 and CH 3 NH 3 PbI 3 at the interface, induce the crystal growth of the perovskite, and play a good role in passivating interfacial defects. Therefore, the interfacial contact and the charge-transfer ability were effectively enhanced. As a result, the addition of HACC and CMCS increased the PCE of C-PSCs from 10.17 to 12.42 and 13.39%, and the repeatability and long-term stability of the corresponding unencapsulated C-PSCs were also significantly improved. This work expands the vision for the future interface modification strategies to improve the device performance and is conducive to promote the further commercialization of C-PSCs.

Hydrogels have been widely applied to the water shutoff in oilfields due to their excellent three-dimensional network and thermal and physicochemical stability, and it is still a huge challenge to develop new hydrogels with simple preparation, low cost, and high mechanical performance that can meet the requirements of practical applications. Herein, we devised a simple and universal manufacturing method for regulating the hydrogen bonds between poly(vinyl alcohol) (PVA) and cellulose nanofibers (CNF) via the water-diffusion action, thus fabricating a physically tough PVA−CNF hydrogel for the in situ water shutoff. This method allowed the polymer chains to strengthen the molecular interactions between polymers upon replacing with water (a poor solvent) to regulate the cross-linking structure, characterizing by the nanocrystallinity domains and fibrillar segments, which also accounted for the thermal stability, extraordinary elasticity, high stretchability, and toughness of PVA−CNF hydrogel. Further, the obtained PVA−CNF hydrogel exhibited superb plugging performance, that is, the breakthrough pressure gradient could reach 71.56 MPa•m −1 , surpassing all currently reported gelling water shutoff agents. This water-induced in situ hydrogelation made it well suited as a water shutoff agent in oilfields and may provide a promising strategy to fabricate mechanically robust smart materials for the water shutoff projects with low cost, simple processing, and high efficiency.

No abstract