Abstract
Control over morphology and crystallinity of metal halide perovskite films is of key importance to enable high-performance optoelectronics. However, this remains particularly challenging for solution-printed devices due to the complex crystallization kinetics of semiconductor materials within dynamic flow of inks. Here we report a simple yet effective meniscus-assisted solution printing (MASP) strategy to yield large-grained dense perovskite film with good crystallization and preferred orientation. Intriguingly, the outward convective flow triggered by fast solvent evaporation at the edge of the meniscus ink imparts the transport of perovskite solutes, thus facilitating the growth of micrometre-scale perovskite grains. The growth kinetics of perovskite crystals is scrutinized by in situ optical microscopy tracking to understand the crystallization mechanism. The perovskite films produced by MASP exhibit excellent optoelectronic properties with efficiencies approaching 20% in planar perovskite solar cells. This robust MASP strategy may in principle be easily extended to craft other solution-printed perovskite-based optoelectronics.
Highlights
Control over morphology and crystallinity of metal halide perovskite films is of key importance to enable high-performance optoelectronics
As state-of-the-art direct bandgap semiconductors, metal halide perovskites capitalize on superior optoelectronic characteristics such as intense broadband absorption, large ambipolar mobility, long charge carrier lifetime, and low processing cost compared with inorganic counterparts[5,6]
Solution printing may not be amenable to high-temperature preparative conditions that are close to the boiling point, Tbp, of typical solvents used for dissolving perovskites (for example, dimethylformamide (DMF), Tbp, DMF 1⁄4 B152 °C; dimethyl sulfoxide (DMSO), Tbp, DMSO 1⁄4 B189 °C), as the ink solution is too volatile to render the control over the crystal morphology
Summary
Control over morphology and crystallinity of metal halide perovskite films is of key importance to enable high-performance optoelectronics This remains challenging for solution-printed devices due to the complex crystallization kinetics of semiconductor materials within dynamic flow of inks. Several solution-processed routes to micrometre-sized perovskite grains by crafting films at high temperatures (for example, spin coating at 180 °C for MAPbI3(1 À x)Cl3x and doctor-blading at 145 °C for FAxMA1 À xPbI3, 0rxr1) have been successfully implemented to reduce the areas of grain boundary and minimize the trap-induced energy loss[16,17] One notion behind these effective approaches is that the grain-boundary motion depends strongly on the temperature, and a high temperature can stimulate solute atoms more to overcome the diffusion energy barrier, resulting in fast grain growth rate[18,19]. We report on a versatile meniscus-assisted solution printing (MASP) strategy to create highly crystallized perovskite films with micrometre-scale grains and preferred crystal orientations at low temperatures for high-efficiency perovskite solar cells. A high PCE approaching 20% is achieved in the planar perovskite solar cells assembled using the MASP-enabled perovskite films as the photoactive layers
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