Search

A polymer-based hole-transporting layer (HTL) with a tunable work function and highest occupied molecular orbital (HOMO) position was demonstrated to effectively optimize the anode junctions of optoelectronic devices. Herein, the perfluorinated ionomer (PFI) was utilized to realize the synthesis of a well-dispersed poly(3,4-ethylene dioxythiophene) (PEDOT) colloid solution, which could be subsequently cast into an efficient HTL. According to the time-of-flight secondary-ion mass spectroscopy and ultraviolet photoelectron spectroscopy analysis, a uniform, interpenetrating PEDOT network with a deep-lying HOMO position could be obtained in the PEDOT:PFI layer. For solar cells, since a deep-lying HOMO position of the HTL was favorable for minimizing the hole injection barrier, a superior organic photovoltaic efficiency of 15.1% and a perovskite solar cell efficiency of 17.8% were achieved. As for organic photodetectors, a deep-lying HOMO position of the HTL was able to reduce the dark current density (JD) by blocking the leakage current under a reverse bias. Utilizing the PEDOT:PFI with an optimized PFI content, an extremely low JD of 6.2 nA cm−2 with an external quantum efficiency of 67% at 1000 nm wavelength was achieved, which sets a benchmark for the emerging near infrared sensing technologies.

Technological implementation of organolead trihalide perovskite (OTP) photovoltaics requires suppression of the surface ionic defects and grain boundaries of OTP films. These surface ionic defects have a detrimental effect on the power conversion efficiency (PCE), are notorious for introducing hysteresis into the current density–voltage (J–V) characteristics, and decrease the stability of perovskite solar cells (PSCs). Here, we report the use of core/shell quantum dots (QDs) as passivation layers on the OTP surfaces to decrease the trap density and, simultaneously, stabilize the OTP chemical structure and extend the charge carrier lifetime. Density functional theory (DFT) calculations indicated that the OTP surface defects and grain boundaries were effectively suppressed by the presence of the CdSe/ZnS QDs. We attribute the lower trap density of the OTP to the Se2− anions from the CdSe/ZnS passivation layer, inducing van der Waals interactions between the organic and inorganic components of the framework. For PSCs featuring CdSe/ZnS QD passivation, the PCE reached close to 20% with diminishing hysteresis of the J–V characteristics and fill factor (FF) of 81.44%. Moreover, the PSCs incorporating the CdSe/ZnS QD passivation layer exhibited long-term stability, retaining 75 and 80% of their initial performance after 2400 and 720 h, respectively. This facile interfacial strategy appears highly applicable for preparing high-performance durable OTP-based high optoelectronic devices.

Recently emerged metal-halide hybrid perovskite (MHP) possesses superb optoelectronic features, which have great attention in solid-state lighting, photodetection, and photovoltaic applications. Because of its excellent external quantum efficiency, MHP acquires enormous potential for manifestation of ultra-low threshold optically pumped laser. However, demonstration of electrical-driven laser remains a challenge because of vulnerable degradation of perovskite, limited exciton binding energy, and intensity quenching and efficiency drop by non-radiative recombinations. In this work, we observed an ultralow-threshold (~ 18 nJcm−2) optically pumped Fabry-Perot (F-P) laser from moisture insensitive mixed dimensional quasi-2D Rudlesden-Popper phase perovskite (RPP) microplates. Unprecedently, we demonstrated electrical-driven F-P laser with threshold ~ 0.15 Acm−2 from quasi-2D RPP by judicious combination of perovskite/hole transport layer (HTL) and electron transport layer (ETL) having suitable band alignment and thickness. Additionally, we showed tunibility of lasing modes by driving external electrical potential. Ultralow-threshold lasing is mainly ascribed by existence of F-P feedback resonance inside RPP microplate, and selective resonance energy transfer mechanism in-between microplates. Performing the finite difference time domain (FDTD) simulations, we confirmed the presence of F-P feedback resonance, and light trapping effect at perovskite/ETL contributing to laser action. Our discovery of electrical-driven laser from MHP opens an alternative avenue in developing optoelectronics.

Metal halide perovskites having three-dimensional crystal structures are being applied successfully in various optoelectronic applications. To address their most challenging issues—instability and toxicity—without losing efficiency, lower-dimensional perovskites appear to be promising alternatives. Recently, two-dimensional (2D) perovskite solar cells have been developed exhibiting excellent photostability and moisture-stability, together with moderate device efficiency. This review summarizes the photophysical properties and operating mechanisms of 2D perovskites as well as recent advances in their applications in solar cell devices. Also presented is an agenda for the next-stage development of stable perovskite materials for solar cell applications, highlighting the issues of stability and toxicity that require further study to ensure commercialization.

Fully inorganic perovskites based on Bi3+ and Sb3+ are emerging as alternatives that overcome the toxicity and low stability of their Pb-based perovskite counterparts. Nevertheless, thin film fabri...

Charge-selective contacts can play a critical role in enhancing the efficiency of perovskite solar cells (PSCs). In this study, we employed fluorine-functionalized graphene (FGr) layers having finely tunable energy levels as hole transport layers (HTLs) to improve the power conversion efficiency (PCE) and stability of inverted PSCs. The non-wetting surface of the FGr enhanced the crystallinity of organic–inorganic perovskites films with large aspect ratios, relative to that of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS). Combining the high work function of the HTL interface with the enhanced crystallinity and limited grain boundary area dramatically decreased the charge recombination losses in organic–inorganic trihalide perovskite (OTP) films. Thus, when incorporating FGr HTLs in inverted PSCs, the best PCE reached 19.34%—the highest efficiency reported to date for any PSC featuring a functionalized graphene HTL. Furthermore, we used this HTL to prepare flexible PSCs and obtained a highest efficiency of 17.50%. Therefore, this highly applicable and facile interface strategy using functionalized graphene HTLs provides stable PSCs displaying high PCEs.

Anatase titanium dioxide (an-TiO2) is often used as the electron transporting material (ETM) in planar-heterojunction perovskite solar cells (PSCs) because of its excellent semiconductor characteristics, outstanding optical transmittance, and suitable band structure. Herein, we report an inexpensive method for mass-scale production of TiO2 ETMs at room temperature (RT ∼ 30 °C), involving the grinding of large clumps of an-TiO2 to form a suspension of TiO2 nanoparticles (NPs) in isopropyl alcohol for meso-superstructured PSCs. This process does not involve any chemical synthesis; it is a purely physical process. The lowest unoccupied molecular orbital (LUMO) of ground an-TiO2 NPs, estimated using ultraviolet photoelectron spectroscopy (UPS), was ca. 4.06 eV, which is a salient feature for the active layer. A regular perovskite solar cell (PSC) based on a CH3NH3PbI3 absorber and ground an-TiO2 ETL exhibited a champion power conversion efficiency (PCE) of 17.43% with an active area of 0.1 cm2. The same ground an-TiO2 NPs were used to fabricate a large-area (designated area: 25.2 cm2) PSC and a PCE of 14.19% was achieved. PSC devices incorporating the ground an-TiO2 NP ETLs exhibited an attractive long-term device stability, with the PCE retaining approximately 85% of the initial values after 80 days.

Inorganic–organic hybrid perovskite solar cells (PSCs) are promising devices for providing future clean energy because of their low cost, ease of fabrication, and high efficiencies, similar to those of silicon solar cells. These materials have been investigated for their potential use in bifacial PSCs, which can absorb light from both sides of the electrodes. Here, we fabricated bifacial PSCs featuring transparent BCP/Ag/MoO3 rear electrodes, which we formed through low-temperature processing using thermal evaporation methods. We employed a comprehensive optical distribution program to calculate the distributions of the optical field intensities with constant thicknesses of the absorbing layer in the top electrode configuration. The best PSC having a transparent BCP/Ag/MoO3 electrode achieved PCEs of 13.49% and 9.61% when illuminated from the sides of the indium tin oxide and BCP/Ag/MoO3 electrodes, respectively. We observed significant power enhancement when operating this PSC using mirror reflectors and...

Pristine MoO3 is a potential anode material for lithium-ion batteries (LIBs), due to its high specific capacity (1117 mA h g−1); it suffers, however, from poor cyclability, resulting from a low conductivity and large volume changes during lithiation/delithiation process. Here we adopt a facile two-step method in which pristine bulk MoO3 is first converted into MoO3 nanorods (MoO3 NR) through mechanical grinding, to buffer the continuous volume changes, and then coated with amorphous carbon through simple stirring and heating, to provide high electronic and ionic conductivities. Electrochemical tests reveal that the carbon-coated MoO3 nanorods (C-MoO3 NRs) exhibit outstanding specific capacity (856 mA h g−1 after 110 cycles at a current density of 0.1 C); remarkable cycle life, among the best reported for carbon-based MoO3 nanostructures (485 mA h g−1 after 300 cycles at 0.5 C and 373 mA h g−1 after 400 cycles at 0.75 C); and greatly improved capacity retention (up to 90.4% after various C-rates) compared to bulk MoO3. We confirm the versatility of the C-MoO3 NR anodes by preparing flexible batteries that display stable performance, even in bent state. This simple approach toward C-MoO3 NR anodes proceeds without rigorous chemical synthesis or extremely high temperatures, making it a scalable solution to prepare high-capacity anodes for next-generation LIBs.

Organic–inorganic lead halide perovskites have recently emerged as highly competitive light absorbing materials for low cost solution-processable photovoltaic devices. With the high efficiency already achieved, removing the toxicity, i.e., lead-free and stability are the key obstacles for perovskite solar cells. Here, we report the synthesis of an antimony (Sb)-based hybrid material having the composition of A3Sb2I9 [A = CH3NH3 (MA), Cs] and an investigation of its potential photovoltaic applications. Sb-based perovskite-like materials exhibited attractive absorbance properties, with the band gaps of MA3Sb2I9 and Cs3Sb2I9 measured to be 1.95 and 2.0 eV, respectively. X-ray photoelectron spectroscopy confirmed the formation of stoichiometric perovskites from appropriate precursor molar ratios incorporated with hydroiodic acid (HI). Planar hybrid Sb-based solar cells exhibited negligible hysteresis and reproducible power output under working conditions. A power conversion efficiency of 2.04% was achieved by the MA3Sb2I9 perovskite-based device—the highest reported to date for a Sb-based perovskite solar cell.

Further technological development of perovskite solar cells (PSCs) will require improvements in power conversion efficiency and stability, while maintaining low material costs and simple fabrication. In this Research Article, we describe top-illuminated ITO-free, stable PSCs featuring microcavity structures, wherein metal layers on both sides on the active layers exerted light interference effects in the active layer, potentially increasing the light path length inside the active layer. The optical constants (refractive index and extinction coefficient) of each layer in the PSC devices were measured, while the optical field intensity distribution was simulated using the transfer matrix method. The photocurrent densities of perovskite layers of various thicknesses were also simulated; these results mimic our experimental values exceptionally well. To modify the cavity electrode surface, we deposited a few nanometers of ultrathin MoO3 (2, 4, and 6 nm) in between the Ag and poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) layers provide hydrophobicity to the Ag surface and elevate the work function of Ag to match that of the hole transport layer. We achieved a power conversion efficiency (PCE) of 13.54% without hysteresis in the device containing a 4 nm-thick layer of MoO3. In addition, we fabricated these devices on various cavity electrodes (Al, Ag, Au, Cu); those prepared using Cu and Au anodes displayed improved device stability of up to 72 days. Furthermore, we prepared flexible PSCs having a PCE of 12.81% after incorporating the microcavity structures onto poly(ethylene terephthalate) as the substrate. These flexible solar cells displayed excellent stability against bending deformation, maintaining greater than 94% stability after 1000 bending cycles and greater than 85% after 2500 bending cycles performed with a bending radius of 5 mm.

Herein, we demonstrate a facile method for transferring thin films to achieve polymer solar cells having stacked structures. By controlling the swelling/de-swelling properties of Polydimethylsiloxane (PDMS) via solvent treatment, we formed uniform organic films upon the PDMS surface and then transferred them to target substrates. We prepared bilayer and graded bilayer structures after transferring indene-C60 bis-adduct (ICBA) and ratio-controlled poly(3-hexylthiophene) (P3HT:ICBA) blends, respectively, onto the P3HT layer. The optimal graded bilayer solar cell exhibited a power conversion efficiency (PCE) of 5.13% an impressive value compared with that obtained for the corresponding bilayer cell (3.67%). We attribute this enhancement in PCE to the greater number of junction interfaces and the balanced carrier transfer properties. This residue-free and place-lift-off transferring method appears to have great promise in the solution processing of multilayer stacked thin film optoelectronics.

A direct deposition methodology has been optimized for highly crystalline inorganic-organic (IO) perovskite thin films. The simplest deposition ensures long-range order with high c-oriented thin films, thicknesses ranging from ultra-thin (~20nm) and upto 1.5 µm. These self-assembled layered perovskites are naturally aligned alternative stacking arrangement of inorganic and organic monolayers, resemble multiple quantum wells (MQWs), which offers superior optoelectronic properties such as room-temperature optical excitons, strong electrically induced photo-carrier mobilities etc. The established fabrication is having device-compatible advantage over other conventional solution–processed thin films wherein the optical features are restricted by thickness limitations (