Transformative Evolution of Organolead Triiodide Perovskite Thin Films from Strong Room-Temperature Solid–Gas Interaction between HPbI₃-CH₃NH₂ Precursor Pair

Abstract

We demonstrate the feasibility of a nonsalt-based precursor pair--inorganic HPbI3 solid and organic CH3NH2 gas--for the deposition of uniform CH3NH3PbI3 perovskite thin films. The strong room-temperature solid-gas interaction between HPbI3 and CH3NH2 induces transformative evolution of ultrasmooth, full-coverage perovskite thin films at a rapid rate (in seconds) from nominally processed rough, partial-coverage HPbI3 thin films. The chemical origin of this behavior is elucidated via in situ experiments. Perovskite solar cells, fabricated using MAPbI3 thin films thus deposited, deliver power conversion efficiencies up to 18.2%, attesting to the high quality of the perovskite thin films deposited using this transformative process.

Inorganic cesium lead halide CsPbX3 nanowires for long-term stable solar cells

“…Fig. 1b shows the morphology of the HPbI3 film, which is constituted by discontinuous, large sized grains and this phenomenon was also found in a recent report [40]. After reaction with CsI, the parent HPbI3 film turned yellow, and surprisingly, nanowires with diameters of 50-100 nm and lengths up to several micrometers tightly covered on the FTO glass could be observed ( Fig.…”

“…Here, HPbI3 having a faster complete reaction with CsI could be attributed to an increased layer lattice, which facilitated the reaction with CsI to form CsPbI3 [38,40].…”

Gas-solid reaction based over one-micrometer thick stable perovskite films for efficient solar cells and modules

“…It is reported that the HPbI 3 films show a hexagonal structure 20,34,36 . Upon increasing MACl content from 0 to 0.20, the low-angle peak around 11.7° shifts to a higher two theta value and the peak intensity increases significantly (Supplementary Fig.…”

“…2, 3) 33,34 . Firstly, we tuned the thickness of perovskite films based on the HPbI 3 –CH 3 NH 2 reaction 20 by varying the substrate temperature (Supplementary Figs. 4, 5, 6, Supplementary Table 2 and Supplementary Note 1).…”

“…This gas−solid reaction-based method introduces a liquid intermediate, which leads to induced morphology reconstruction, defects healing 19,20 . Meanwhile, CH 3 NH 2 gas treatment can help reduce the defect density in perovskite films 19,20 and also elimination of I 2 13 . Besides, CH 3 NH 2 -induced δ-NH 2 CH=NH 2 PbI 3 in (CH 3 NH 3 ) x (NH 2 CH=NH 2 ) 1− x PbI 3 is also reported to passivate trap states to improve device performance 21 .…”