Strengthened Perovskite/Fullerene Interface Enhances Efficiency and Stability of Inverted Planar Perovskite Solar Cells via a Tetrafluoroterephthalic Acid Interlayer

Abstract

In this work, a novel back contact interface engineering is developed for inverted planar perovskite solar cells, in which a tetrafluoroterephthalic acid (TFTPA) interlayer is inserted between CH 3 NH 3 PbI 3 and PC 61 BM to strengthen the interface contact. Benefiting from the strong Coulombic interactions between positive electron-poor tetrafluoroterephthalate moieties and negative electron-rich fullerene molecules, as well as the coordinate effect between −COOH groups of TFTPA and Pb 2+ ions of perovskites surface, a tightly jointing and defectpassivated CH 3 NH 3 PbI 3 /PC 61 BM interface is formed. The strengthened CH 3 NH 3 PbI 3 /PC 61 BM back contact can significantly facilitate electron transport and simultaneously diminish the charge accumulation and recombination. Therefore, power conversion efficiency (PCE) of the TFTPA device is up to 19.39%, whereas the hysteresis effect is weak, and the PCE is improved by 20.4% compared with the control device which does not have a TFTPA interlayer. Particularly, the moisture stability of the TFTPA device is greatly improved as compared to the control device. Our findings illustrate that the back contact interface engineering is an important and promising approach for inverted planar perovskite solar cells.

Interfacial stabilization for inverted perovskite solar cells with long-term stability

“…16 Therefore, interfacial stabilization at the interface of PVK/ETL is crucial for achieving both high efficiencies and long-term stabilities in inverted p-i-n PSCs. While the performance improvements have been demonstrated by various approaches, 3,6,,13,15,17-22 including the use of different inorganic 13,17 or organic 15,[18][19][20] interfacial layers between PVK and C60, further performance improvements are still needed to bring these devices closer to commercialization. 7 Here we use a boron chloride subphthalocyanine (Cl6SubPc)/fullerene ETL to simultaneously reduce the interfacial defect density and hinder ion migration, resulting in power conversion efficiencies of 22.0% (certified 21.3 %), a shelf life of 7000 hours, T80 of 816 h under damp heat stress, and performance retention of 98% after 2000 hours at 80 o C in inert environment, and 95% after 1200 h outdoor testing (first outdoor performance test for inverted devices).…”

Synergistic Effect of Excited State Property and Aggregation Characteristic of Organic Semiconductor on Efficient Hole‐Transportation in Perovskite Device

“…For reference, V bi values were calculated with the following equation: C −2 = 2( V bi − V )( A 2 eεε o N A ) −1 , where A is the active device area and N A is the doping concentration. [ 37,38 ]…”

“…where A is the active device area and N A is the doping concentration. [37,38] Meanwhile, the organic HTMs have strong absorption in UV region, and this is beneficial to block the UV light that can degrade perovskite layer. X-ray diffraction (XRD) patterns in Figure 4e show that PbI 2 -related peaks are generated from the perovskite prepared on ITO/bare NiO x after 12 h continuous UV light-illumination (365 nm, 15 mW cm −2 , and illumination .…”

Barrier Designs in Perovskite Solar Cells for Long‐Term Stability

“…Organic materials with long alkyl chains or other hydrophobic groups could restrict the ingress of moisture. [129][130][131][132] The shielding effect can be further enhanced when conjugated and cross-linked polymers with network structures are used, which can prevent the outward ion diffusion from perovksite. [133][134][135][136] One important advantage of organic materials is their flexibility, which is benefit for the formation of compact wrapping layer around perovskites.…”

“…After storage of 30 days at RT in a 30% RH condition, the controlled device kept 78% of the initial PCE while the TFTPA based device still retained 92% of its initial efficiency. [132] Huang et al introduced a poly(ethylene-co-vinyl acetate) (EVA) glued layer between www.advancedsciencenews.com MAPbI 3 and PCBM as barrier layer to improve the interfacial contact and also to improve the resistance of perovskite against moisture and ion diffusion ( Figure 4h). [135] It was found that perovskite with EVA presented superior hydrophobicity, with a contact angle of ≈103.6°, remarkably larger than the pristine one (≈72.5°).…”