Fluorocarbon Surfactant‐Assisted Large‐Area Uniform and Water‐Resistant Perovskite Films for Efficient Photovoltaics

Abstract

Formamidinium (FA)‐based lead triiodide perovskites are suitable light‐absorbing materials for solar cells due to their narrow bandgap, long‐range charge diffusion length, and excellent thermal stability. However, large‐area uniformity and phase purity are still challenging issues in the two‐step solution processed perovskite films because of the incomplete spreading/reacting of the organic amine salt solution. Herein, a novel multifunctional nonionic fluorocarbon surfactant (FS) is introduced to improve the crystallization of perovskites via the strategy of reducing the surface tension of the organic amine salt solution and facilitating the adequate binding of the organic amine salts with PbI2. Moreover, the FS additives effectively reduce residual PbI2; passivate the surface and interfacial defects of perovskites. The FS modified perovskite solar cells (PSCs) exhibit a champion power conversion efficiency (PCE) of 21.72% (0.16 cm2) with an enhanced stability, and the unencapsulated device maintains about 80% of the initial PCE even after 1000 h of storage. In addition, the larger PSCs with the active area of 1.00 cm2 deliver a peak PCE of 19.19%. Eventually, FS impedes moisture intrusion and effectively mitigates the decomposition of perovskite film. This work opens the way to explore large‐area PSCs with high performance and long‐term stability.

Eliminating Voids and Residual PbI2 beneath a Perovskite Film via Buried Interface Modification for Efficient Solar Cells

“…Notably, in the control PVK film, there are two small Pb 0 peaks located at 141.9 and 137.6 eV in addition to Pb 4f 5/2 and Pb 4f 7/2 at 143.8 and 138.8 eV, respectively. The presence of Pb 0 confirms the two-phase coexistence in the PVK film . However, the Pb 0 peaks in the MADH-modified films are not obvious, which is consistent with the SEM observation.…”

“…The presence of Pb 0 confirms the two-phase coexistence in the PVK film. 45 However, the Pb 0 peaks in the MADH-modified films are not obvious, which is consistent with the SEM observation. Meanwhile, the MADHmodified films exhibit a slight red shift for the I 3d peak (Figure 2e).…”

Surface-anchoring fluorinated sulfonate enables efficient and stable perovskite photovoltaics

“…S9 (ESI†), the TFS-TFMS modified film shows obviously charactered peaks of F 1s at 688.32 eV, S 2p at 168.08 eV and C–F at 292.45 eV relative to the control one, further indicating that TFS-TFMS was indeed deposited on perovskite films. 27,37–40 As described in Fig. 3b, the Pb 4f spectrum of the control perovskite film depicted four peaks, where the Pb–I peaks were located at 137.93 eV of 4f 7/2 , and 142.81 eV of 4f 5/2 , and the detrimental Pb 0 peaks were located at 136.41 and 141.33 eV.…”