Crystallization Control of Methylammonium‐Free Perovskite in Two‐Step Deposited Printable Triple‐Mesoscopic Solar Cells

Abstract

The evolution from the original methylammonium (MA)‐ to formamidinium (FA)‐dominated perovskite makes a crucial contribution to improve the photoelectric performance of perovskite solar cells (PSCs) in a decade. However, to obtain α‐FAPbI3, annealing temperature above 100 °C is essential. In addition, it is still challenging to deposit a uniform and high‐quality FA‐based perovskite absorber in printable triple‐mesoscopic PSC due to the complicated mesoscopic structure. Herein, a low‐temperature, two‐step sequential deposition method is used for pure FAPbI3 perovskite in printable triple‐mesoscopic PSC. By using different lead sources, the crystallization and morphology of lead iodide (PbI2) are finely controlled, which modulates the crystallization and pore filling of perovskite in mesoscopic structure. The improved interface contact promotes the transfer of charge carrier from perovskite to TiO2. With the further introduction of cesium bromide (CsBr) into lead precursor, a power conversion efficiency of 16.24% is achieved. This study provides a deeper understanding of the pore filling and crystallization for both PbI2 and perovskite, and helps explore and optimize the deposition process of perovskite in mesoscopic structure.

Tailoring the Dimensionality of Hybrid Perovskites in Mesoporous Carbon Electrodes for Type‐II Band Alignment and Enhanced Performance of Printable Hole‐Conductor‐Free Perovskite Solar Cells

“…By tuning the composition and crystallization of perovskite absorbers in the mesoporous scaffold, [ 13–15 ] modifying the mesoporous scaffold and interfaces [ 16,17 ] and developing novel deposition technique, [ 14 ] the efficiency of triple‐mesoscopic PSCs has been improved from the initial 6% to current 16.51%. [ 9,16,18,19 ] Particularly, the devices have been suffering severe potential loss, and thus showed low open‐circuit voltage ( V OC , 0.85–0.95 V). In one hand, the mesoporous scaffold is micrometer‐thick, which determines the charge diffusion length in the device.…”

Minimizing the Voltage Loss in Hole‐Conductor‐Free Printable Mesoscopic Perovskite Solar Cells

“…

Nevertheless, the efficiency of the printable mesoscopic PSCs still lags behind the conventional PSCs. Though extensive methods have been conducted to improve the performance of such devices, including additives, [12][13][14][15][16] composition engineering, [17,18] and crystallization control, [18][19][20] the highest PCE reported so far is 18.2% using an acetamidinium mixed methylammonium lead iodide perovskite. [21] In the meantime, though FAPbI 3 perovskites are believed and reported to yield higher PCEs, we only achieved a PCE of ≈16% using FAPbI 3 perovskite.

…”

Beneficial effects of cesium acetate in the sequential deposition method for perovskite solar cells

“…During the film formation process, strong interaction between Acand Pb 2+ plays a significant role in the improved quality of resulting perovskite films. Moreover, various previous reports have confirmed that Ac -(in form of PbAc 2, FAAc, MAAc) is engaged in the perovskite growth process, leading to larger grains, and reducing defects [35][36][37] .…”