An Equalized Flow Velocity Strategy for Perovskite Colloidal Particles in Flexible Perovskite Solar Cells.

The non-uniform distribution of colloidal particles in perovskite precursor results in an imbalanced response to the shear force during flexible printing process. Herein, it is observed that the continuous disordered migration occurring in perovskite inks significantly contributes to the enlargement of colloidal particles size and diminishes the crystallization activity of the inks. Therefore, a molecular encapsulation architecture by glycerol monostearate to mitigate colloidal particles collisions in the precursor ink, while simultaneously homogenizing the size distribution of perovskite colloids to minimize their diffusion disparities, is devised. The utilization of colloidal particles with a molecular encapsulation structure enables the achievement of uniform deposition during the printing process, thereby effectively balancing the crystallization rate and phase transition in the film and facilitating homogeneous crystallization of perovskite films. The large-area flexible perovskite device (1.01 cm2 and 100 cm2) fabricated through printing processes, achieves an efficiency of 24.45% and 15.87%, respectively, and manifests superior environmental stability, maintaining an initial efficiency of 91% after being stored in atmospheric ambiences for 150 days (unencapsulated). This work demonstrates that the dynamic evolution process of colloidal particles in both the precursor ink and printing process represents a crucial stride toward achieving uniform crystallization of perovskite films.

A Bionic Interface to Suppress the Coffee-Ring Effect for Reliable and Flexible Perovskite Modules with a Near-90% Yield Rate.

The inhomogeneity, poor interfacial contact, and pinholes caused by the coffee-ring effect severely affect the printing reliability of flexible perovskite solar cells (PSCs). Herein, inspired by the bio-glue of barnacles, a bionic interface layer (Bio-IL) of NiOx /levodopa is introduced to suppress the coffee-ring effect during printing perovskite modules. The coordination effect of the sticky functional groups in Bio-IL can pin the three-phase contact line and restrain the transport of perovskite colloidal particles during the printing and evaporation process. Moreover, the sedimentation rate of perovskite precursor is accelerated due to the electrostatic attraction and rapid volatilization from an extraordinary wettability. The superhydrophilic Bio-IL affords an even spread over a large-area substrate, which boosts a complete and uniform liquid film for heterogeneous nucleation as well as crystallization. Perovskite films on different large-area substrates with negligible coffee-ring effect are printed. Consequently, inverted flexible PSCs and perovskite solar modules achieve a high efficiency of 21.08% and 16.87%, respectively. This strategy ensures a highly reliable reproducibility of printing PSCs with a near 90% yield rate.

Wearable Tin-Based Perovskite Solar Cells Achieved by a Crystallographic Size Effect.

Tin-based perovskite solar cells (PSCs) demonstrate a potential application in wearable electronics due to its hypotoxicity. However, poor crystal quality is still the bottleneck for achieving high-performance flexible devices. In this work, graphite phase-C3 N4 (g-C3 N4 ) is applied into tin-based perovskite as a crystalline template, which delays crystallization via a size-effect and passivates defects simultaneously. The double hydrogen bond between g-C3 N4 and formamidine cation can optimize lattice matching and passivation. Moreover, the two-dimensional network structure of g-C3 N4 can fit on the crystals, resulting an enhanced hydrophobicity and oxidation resistance. Therefore, the flexible tin-based PSCs with g-C3 N4 realize a stabilized power conversion efficiency (PCE) of 8.56 % with negligible hysteresis. In addition, the PSCs can maintain 91 % of the initial PCE after 1000 h under N2 environment and keep 92 % of their original PCE after 600 cycles at a curvature radius of 3 mm.