Isomer‐Pure Bis‐PCBM‐Assisted Crystal Engineering of Perovskite Solar Cells Showing Excellent Efficiency and Stability

Abstract

We prepared the novel fullerene derivative (a-bis-PCBM) by separating it from the as-produced bis-phenyl-C 61 -butyric acid methyl (bis-[60] PCBM) ester isomer mixture using preparative peak-recycling high performance liquid chromatography (HPLC). We employed the compound as a templating agent for the solution processing of metal halide perovskite films by the antisolvent method. Perovskite solar cells (PSCs) containing a-bis-PCBM perovskite achieve better stability, efficiency, and reproducibility compared with those employing traditional PCBM. The a-bis-PCBM can fill the vacancies and grain boundaries of the perovskite film, enhancing the crystallization of perovskites and addressing the issue of 2 slow electron extraction. In addition, it can also resist the ingression of moisture, protect the interfaces from chemical erosion, and passivate the voids or pinholes generated in the holetransporting layer. As a result, we obtain an outstanding power conversion efficiency (PCE) of 20.8 % compared with 19.9 % by PCBM, accompanied by excellent stability under heat and simulated sunlight,. The PCE of unsealed devcies dropped by less than 10% in ambient air (40% RH) after 44 days at 65 ℃ and by 4% after 600 h under continuous full sun illumination and maximum power point tracking respectively.Hybrid organic-inorganic lead halide perovskite solar cells (PSCs) have emerged as a promising candidate for the next generation photovoltaic technology due to their low manufacturing cost and high performance. 1−6 Through judicious manipulation of perovskite morphology and improvement of interfacial properties, 2−6 PSCs have reached a certified power conversion efficiency (PCE) up to 22.1%. 7 Generally, the PSCs with the best performance employ a sandwich configuration, composed of a layer of TiO 2 electron selective contact, which is infiltrated by the intrinsic perovskite light harvester, followed by a layer of hole transport material (HTM) as p-type contact and a metal back contact. 8 Despite of these stunning advances, several challenges still remain before PSCs become a competitive commercial technology, one crucial issue being the device stability. 9−11 Uncontrolled film morphology associated with poor crystallity of the perovskites results in low efficiency and poor reproducibility of the device performance. 12 Previous studies have indicated that the degradation of PSCs is primarily governed by the ingress of atmospheric oxygen and water vapor into the film upon exposure to air, which in turn causes undesired reactions with the active materials. 13,14 Various methods have been tried to modify the morphology of perovskite films aiming to improve the stability, for example, poly(methyl methacrylate) (PMMA) was used as a template to control nucleation and crystal growth, resulting in considerable increase in both the device efficiency and stability when kept under 3 dry condition in the dark. 15 Other studies use additives like 1-methyl-3-(1H,1H,2H,2H-nonafluorohexyl)-imidazolium iodide, 16 or phenyl-C 61 -b...

Carrier Interfacial Engineering by Bismuth Modification for Efficient and Thermoresistant Perovskite Solar Cells

“…The equivalent circuit model is composed of series resistance (R s ) at high frequency (≈100 kHz) and carrier recombination resistance (R rec ) at low frequency(0.1-100 Hz) and a capacitor (C rec ). [44,45] PL spectra of perovskite samples on glass substrates are shown in inset of Figure 2d, where the PL intensity of the film is increased by about 20% after MB 1.5 modification (inset of Figure 2d). The MB 1.5 modified device exhibits an increased R rec (434.3 Ω cm 2 ) than that of the control device (380.0 Ω cm 2 ).…”

Efficient Passivation of Hybrid Perovskite Solar Cells Using Organic Dyes with COOH Functional Group

“…[1][2][3][4] The highest certified power conversion efficiency (PCE) has exceeded 22% in just a few years due to a series of advanced optimizations in terms of material, [5][6][7][8] interface [9][10][11][12] and fabrication technologies. [1][2][3][4] The highest certified power conversion efficiency (PCE) has exceeded 22% in just a few years due to a series of advanced optimizations in terms of material, [5][6][7][8] interface [9][10][11][12] and fabrication technologies.…”

Impact of fullerene derivative isomeric purity on the performance of inverted planar perovskite solar cells

“…Grätzel et al 39 recently reported that improved device performance and stability in PSCs can be obtained when using a pure bis-adduct of PC 61 BM as an additive in an antisolvent chlorobenzene solution. Since the packing of the C 70 fullerene derivatives in the solid state should have an impact on their charge separation and transporting properties in PSCs, the three obtained isomers were purified and characterized in this work, but only the pure α-DMEC 70 was evaluated as the ETM in inverted PSCs since this compound was the major regioisomer obtained.…”