Multichannel Interdiffusion Driven FASnI₃ Film Formation Using Aqueous Hybrid Salt/Polymer Solutions toward Flexible Lead‐Free Perovskite Solar Cells

Abstract

Tin (Sn)-based perovskites are increasingly attractive because they offer lead-free alternatives in perovskite solar cells. However, depositing high-quality Sn-based perovskite films is still a challenge, particularly for low-temperature planar heterojunction (PHJ) devices. Here, a "multichannel interdiffusion" protocol is demonstrated by annealing stacked layers of aqueous solution deposited formamidinium iodide (FAI)/polymer layer followed with an evaporated SnI layer to create uniform FASnI films. In this protocol, tiny FAI crystals, significantly inhibited by the introduced polymer, can offer multiple interdiffusion pathways for complete reaction with SnI . What is more, water, rather than traditional aprotic organic solvents, is used to dissolve the precursors. The best-performing FASnI PHJ solar cell assembled by this protocol exhibits a power conversion efficiency (PCE) of 3.98%. In addition, a flexible FASnI -based flexible solar cell assembled on a polyethylene naphthalate-indium tin oxide flexible substrate with a PCE of 3.12% is demonstrated. This novel interdiffusion process can help to further boost the performance of lead-free Sn-based perovskites.

Synergy Effect of Both 2,2,2‐Trifluoroethylamine Hydrochloride and SnF2 for Highly Stable FASnI3−xClx Perovskite Solar Cells

“…Figure b shows the cross‐section SEM image of the typical device structure, where the FASnI 3−x Cl x absorber layer is around 250 nm thick, which is comparable to previous reports of FASnI 3 devices . PEDOT:PSS film (≈50 nm) was employed as hole transport layer (HTL) owing to good match in valence band maximum (VBM) of FASnI 3 . A combination of PCBM (ca.…”

Improving Performance of Lead‐Free Formamidinium Tin Triiodide Perovskite Solar Cells by Tin Source Purification

“…Given that the oxidation is inevitable, either introduced during synthesis or storage, there is always some Sn 4+ mixed in the SnX 2 source . Different synthetic methods and purity of SnX 2 influence the device performance and even different batchs from the same commercial source may result in different functional photovoltaic devices according to our experience. For example, Kumar et al pointed out that the 99% SnI 2 did not result in functional PSCs and 99.99% SnI 2 was the optimum, taking the wettability problem of 99.999% SnI 2 into consideration .…”

High‐Quality Cs2AgBiBr6 Double Perovskite Film for Lead‐Free Inverted Planar Heterojunction Solar Cells with 2.2 % Efficiency

“…[8][9][10] As a consequence, many researches have turned their attention to the exploration of Pb-free perovskite material with high ambient stability and low toxicity. [16][17][18][19] However, the easy oxidation of Sn 2 + to Sn 4 + has a great impact on the stability of the Sn-based perovskite material, which is considered to be the fatal limitation for its development as light absorber. [16][17][18][19] However, the easy oxidation of Sn 2 + to Sn 4 + has a great impact on the stability of the Sn-based perovskite material, which is considered to be the fatal limitation for its development as light absorber.…”