Direct Laser Writing of δ- to α-Phase Transformation in Formamidinium Lead Iodide

Abstract

Organolead halide perovskites are increasingly considered for applications well beyond photovoltaics, for example, as the active regions within photonic devices. Herein, we report the direct laser writing (DLW: 458 nm cw-laser) of the formamidinium lead iodide (FAPbI3) yellow δ-phase into its high-temperature luminescent black α-phase, a remarkably easy and scalable approach that takes advantage of the material’s susceptibility to transition under ambient conditions. Through the DLW of α-FAPbI3 tracks on δ-FAPbI3 single-crystal surfaces, the controlled and rapid microfabrication of highly luminescent structures exhibiting long-term phase stability is detailed, offering an avenue toward the prototyping of complex perovskite-based optical devices. The dynamics and kinetics of laser-induced δ- to α-phase transformations are investigated in situ by Raman microprobe analysis, as a function of irradiation power, time, temperature, and atmospheric conditions, revealing an interesting connection between oxygen intercalation at the surface and the δ- to α-phase transformation dynamics, an insight that will find application within the wider context of FAPbI3 thermal phase relations.

Formamidinium‐Based Lead Halide Perovskites: Structure, Properties, and Fabrication Methodologies

“…This conversion typically occurs quickly, within 24 h . Surprisingly, it was reported that a more stable conversion to the α‐phase can be achieved by direct laser writing, with phase stability demonstrated over a period of four weeks . While the obtained results are interesting from the perspective of a fundamental understanding and possible uses for some specific applications requiring material patterning, large‐area devices such as solar cells require different methods for phase stabilization.…”

“…[48] Annealing above 150-160 °C results in a reversible transition to the α-phase, but the crystals typically revert to the δ phase upon storage in an ambient environment. [39,48] This conversion typically occurs quickly, within 24 h. [46,47] Surprisingly, it was reported that a more stable conversion to the α-phase can be achieved by direct laser writing, with phase stability demonstrated over a period of four weeks. [39] Small Methods 2018, 2, 1700387 [8,14] a-c) Reproduced with permission.…”

Perovskite Solar Cells: From the Laboratory to the Assembly Line

“…High‐efficiency PSCs have been mostly prepared in an oxygen‐ and moisture‐free glove‐box atmosphere . However, processes requiring a sub‐ppm H 2 O content surely represent a restriction to the industrialization of PSCs, especially when it is considered that there is a lack of effective solutions to this problem until now …”

“…[107][108][109][110] However, processes requiring as ub-ppm H 2 Oc ontent surely represent ar estriction to the industrialization of PSCs, especially when it is considered that there is al ack of effective solutionst ot his problem until now. [29,[111][112][113] Among the attempts to address this issue, Taie tal. reported the use of aP b(SCN) 2 precursor in preparingP SCs in ambient air,o btaining high-quality CH 3 NH 3 PbI 3Àx (SCN) x films even when the relative humidity exceeded 70 % [114] ( Figure 5AB).…”

“…E) Digital picture of the resulting PSC. Adapted and reprinted with permissionf rom references[105,110,113].…”