High-performance flexible and air-stable perovskite solar cells with a large active area based on poly(3-hexylthiophene) nanofibrils

Abstract

Flexible metal halide perovskite solar cells (PSCs) have been considered promising wearable energy power sources. Recently, various multi-functional charge-transporting layers, with high conductivity and air stability, have been rapidly developed in order to improve device performance. The practical use of flexible PSCs requires the retention of the performance and air stability at large active areas. However, increasing the size of the active layer results in increased contact and series resistance at the interfaces of the device. This hinders the charge transport, leading to charge recombination and degradation of the device performance. Furthermore, the poor stability of organic small molecules is detrimental to longterm stability. As such, flexible PSCs based on Li-doped poly(3-hexylthiopehene) (P3HT) nanofibrils (LN-P3HT), as a hole transporting layer (HTL), are prepared by subjecting a P3HT solution to a cooling process. The nanofibrils obtained via the p-conjugation of the thiophene rings result in improved conductivity and air stability, yielding high-performance, flexible, and air-stable PSCs with an active area of 1 cm 2 (PCE ¼ 13.12%). This outstanding performance and mechanical stability are retained (PCE ¼ 12.96%) after 500 bending cycles at r ¼ 15 mm; these PSCs also exhibit a 30-day PCE retention of 87% (relative to the initial PCE) at a relative humidity of 30%. Therefore, this novel and facile strategy for preparing an efficient and air-stable organic HTL is a promising method for the realization of highperformance large-area flexible PSCs.

Magnesium‐doped Zinc Oxide as Electron Selective Contact Layers for Efficient Perovskite Solar Cells

“…We further optimizedt he thickness of 10 %Z MO layers for optimization of the device performance. [36] To correlatet he Mg doping and the resultant PSC performance, measurements of optical absorption, photoelectron spectroscopy,a nd electrical impedance were carriedo ut. ZMO films with 10, 25, and 40 nm thickness were prepared by using varied precursor sol concentrations of 0.2, 0.4, and 0.6 m in spin coating, respectively.F igure S5 gives the J-V characteristicso ft he PSCs based on varied ZMO thickness.…”

“…This reduced hysteresis suggests that there might be al ower contact resistance at the ZMO/perovskite interface and the Mg doping provides improved charge extraction from the perovskite. [36] To correlatet he Mg doping and the resultant PSC performance, measurements of optical absorption, photoelectron spectroscopy,a nd electrical impedance were carriedo ut. Given that the shield effect of the ITO substrate causes difficulty in identifying the absorption edges from the transmission spectra, [34] we measuredt he transmission spectra of all ZMO films on quartz glass to determine the band gaps.…”

Recent progress in stabilizing hybrid perovskites for solar cell applications

“…[200] Li-doped P3HT nanofibrils (LP-P3HT)-based flexible PSCs exhibited good mechanical stability (retaining a PCE of 12.96% after 500 bending cycles at r=15 mm) and air stability (retaining 87% of the initial PCE after storage in ambient condition (30% RH) for 30 d). [201] Kazunari Matsuda et al [202] reported an all carbon SWNT/GO/PMAA HTMbased PSC, exhibiting significantly enhanced stability (PCE changing slightly from 10.5% to 10.0% during 10 days storage in air (70-80% RH) at room temperature) in comparison with spiro-OMeTAD based device (PCE declining from10.5% to 5.8% in the same condition). Introducing hydrophobic alkyl chains into HTMs can improve the stability of the PSCs because of the enhanced moisture resistance of the HTMs.…”

Recent Progress of Flexible Perovskite Solar Cells

“…PCBM film might be the most frequently used fullerene derivative ETL in PSCs, because it not only can be simply prepared by a spin‐coating process without any further treatment but also reduce the density of trap states and passivate the grain boundaries of the perovskite absorber. So far, n‐i‐p type FPSCs with PCEs of 11.1–13.12% have been reported by several groups using different HTLs . As shown in Figure a, an extremely thin layer of PEIE was used to modify the surface of the TCO in such devices, which was believed to decrease the surface work function of ITO and facilitate electron extraction into the electrode via fullerene derivatives (Figure b) .…”