An investigation of phase distribution demonstrated that PCDTBT was embedded in PTB7-Th and ITIC, and hence introduced dual FRET effects in the resulting ternary system.
Layered perovskite films, composed of two-dimensional (2D) Ruddlesden− Popper perovskites (RPPs), show improved stability compared to their conventional threedimensional (3D) counterparts in perovskite solar cells (PSCs). However, 2D PSCs exhibit a lower power conversion efficiency (PCE), which has been attributed to compositional inhomogeneity and nonuniform alignment of the 2D perovskite phases. Methylammonium chloride (MACl) has been adopted as an additive to improve the PCE and the operational stability of 2D PSCs, although the role of MACl in performance enhancement is unclear. In this work, time-and spatially resolved fluorescence and absorption techniques have been applied to study the composition and charge carrier dynamics in MACl-doped BA 2 MA 4 Pb 5 I 16 (⟨n⟩ = 5) layered perovskite films. The inhomogeneous phase orientation distribution in the direction orthogonal to the substrate for undoped layered perovskite films undergoes reorganization upon MACl doping. Based on structural and crystallographic analyses, it is revealed that MACl can facilitate the crystallization of small-n 2D perovskite phases at the cost of consuming an increased amount of BA cations. Consequently, an increase in the thickness of large-n 2D perovskite phases accompanies their enhanced perpendicular alignment ([101] crystalline orientation) to the substrate, which facilitates charge carrier transport and collection by electrodes. The defect passivation of the MACl-doped layered perovskite film provided by the small-n phase is also beneficial to the photovoltaic performance of the PSC device. A maximum PCE (∼14.3%) was achieved at 6 mol % MACl doping, with this optimum level influenced by the increased interfacial roughness of the layered perovskite film caused by the edges of smalln perovskite flakes emerging on the front surface.
Abstract:The surface plasmon resonance (SPR) of metallic nanomaterials, such as gold (Au) and silver (Ag), has been extensively exploited to improve the optical absorption, the charge carrier transport, and the ultimate device performances in organic photovoltaic cells (OPV). With the incorporation of diverse metallic nanostructures in active layers, buffer layers, electrodes, or between adjacent layers of OPVs, multiple plasmonic mechanisms may occur and need to be distinguished to better understand plasmonic enhancement. Steady-state photophysics is a powerful tool for unraveling the plasmonic nature and revealing plasmonic mechanisms such as the localized surface plasmon resonance (LSPR), the propagating plasmon-polariton (SPP), and the plasmon-gap mode. Furthermore, the charge transfer dynamics in the organic semiconductor materials can be elucidated from the transient photophysical investigations. In this review article, the basics of the plasmonic mechanisms and the related metallic nanostructures are briefly introduced. We then outline the recent advances of the plasmonic applications in OPVs emphasizing the linkage between the photophysical properties, the nanometallic geometries, and the photovoltaic performance of the OPV devices.
Bulk-heterojunction (BHJ) blends
are commonly used as active materials
for optoelectronics. Ordering of molecular packing in blends is critical
to their electronic properties, spurring investigation on how to obtain
BHJ with long-range ordering. However, the difficulty in controlling
crystallization during blending limits the crystallinity. Developing
a new strategy instead of conventional blending is, thus, needed.
Inspired by biomineralization, here, C60 single-crystals
are prepared in organogel matrix of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenvinylene]
(MEH-PPV) to form MEH-PPV:C60 composites. Essentially,
networks of MEH-PPV are incorporated into growing C60 crystals
and penetrate throughout the crystals, resulting in crystal/gel-network
interpenetrating composites. Despite the coexistence of MEH-PPV, the
C60 crystalline component maintains single-crystallinity
and the composite exhibits as BHJ with long-range ordering. Furthermore,
compared with blends, the long-range ordered BHJ shows a higher efficiency
of charge dissociation and better performance in photodetection, exemplifying
the advantage of ordering on organic electronics. Hence, this work
provides a new platform to study BHJ with long-range ordering.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.