We investigate the morphological and performance of organic photovoltaics based on blended films of alternating poly(thiophene-phenylene-thiophene) and [6,6]-phenyl-C(71)-butyric acid methyl ester (PC(71)BM). The resulting fine-scale phase separation leads to enhanced performance and the highest power efficiency (6.4% under AM 1.5G (100 mW cm(-2))) when we use solvent annealing process.

A cadmium-free CuInS2 quantum dot (QD)-sensitized solar cell (QDSC) has been fabricated by taking advantage of the ex situ synthesis approach for fabricating highly crystalline QDs and the in situ successive ionic-layer adsorption and reaction (SILAR) approach for achieving high surface coverage of QDs. The ex situ synthesized CuInS2 QDs can be rendered water soluble through a simple and rapid two-step method under the assistance of ultrasonication. This approach allows a stepwise ligand change from the insertion of a foreign ligand to ligand replacement, which preserves the long-term stability of colloidal solutions for more than 1 month. Furthermore, the resulting QDs can be utilized as sensitizers in QDSCs, and such a QDSC can deliver a power conversion efficiency (PCE) of 0.64%. Using the SILAR process, in situ CuInS2 QDs could be preferentially grown epitaxially on the pre-existing seeds of ex situ synthesized CuInS2 QDs. The results indicated that the CuInS2 QDSC fabricated by the combined ex situ/in situ growth process exhibited a PCE of 1.84% (short-circuit current density = 7.72 mA cm(-2), open-circuit voltage = 570 mV, and fill factor = 41.8%), which is higher than the PCEs of CuInS2 QDSCs fabricated by ex situ and in situ growth processes, respectively. The relative efficiencies of electrons injected by the combined ex situ/in situ growth approach were higher than those of ex situ synthesized CuInS2 QDs deposited on TiO2 films, as determined by emission-decay kinetic measurements. The incident photon-to-current conversion efficiency has been determined, and electrochemical impedance spectroscopy has been carried out to investigate the photovoltaic behavior and charge-transfer resistance of the QDSCs. The results suggest that the combined synergetic effects of in situ and ex situ CuInS2 QD growth facilitate more electron injection from the QD sensitizers into TiO2.

solar cells, and organic light emitting diodes. Because their perovskite precursors are commercially available, the study of PSCs has recently become an important emerging scientific field. [1] Today, the critical issues for PSC development are related to increasing their performance and stability. [2] Because the short-circuit current densities (J sc ) of PSC devices have almost approached their theoretical limit, efforts directed toward further increasing the performance have been based on increasing their open-circuit voltages (V oc ) and fill factors (FFs). Such approaches will necessitate optimizing the morphology, the interfacial layers, the device architectures, and the hole/electron transporting layers. [3] With advances in device engineering and materials, the power conversion efficiencies (PCEs) of PSCs have skyrocketed from 3.8% to 22.7% within the last six years. [1e,f,3c,4] Efforts at optimizing the morphologies of PSC films (i.e., their grain size, coverage, and crystallinity) have directly led to greater PSC performance. For example, variations in the solvents, thermal engineering techniques, and additives have all played roles in improving the quality of the resulting perovskite films. [5] Many types of additives-including metal/organic halide salts, solvents, Lewis bases, [6] inorganic acids, polymers, [7] and fullerenes-can enhance the morphologies and efficiencies of PSCs. [8] Considering the complexity of perovskite formation, the vast array of fabrication parameters, and the myriad materials that can be involved in the process, there remains plenty of room for new discoveries in this field.Because perovskite films are generally prepared through solution processes, the presence of defects-ones that cause nonradiative energy loss and decrease the values of V oc and efficiencies-is unavoidable. Tuning the composition to passivate the defects of perovskites (using such materials as pyridine [9] and polymers [8a] ) can be an efficient means of improving the performance of PSCs. In this present study, we employed carbon nanodots (CNDs) as additives that efficiently tailor the optoelectronic properties of perovskites. Because of their nanoscale dimensions, tunable optoelectronic properties, and ready synthesis (to present various functional groups), the study of CNDs has experienced rapid development, especially for Carbonized bamboo-derived carbon nanodots (CNDs) as efficient additives for application in perovskite solar cells (PSCs) are reported. These carboxylic acid-and hydroxyl-rich CNDs interact with the perovskite through hydrogen bonds and, thereby, promote the carriers' lifetimes and realize high-performance p-i-n PSCs having the structure indium tin oxide/ NiO x /CH 3 NH 3 PbI 3 (MAPbI 3 )/PC 61 BM/BCP/Ag. As a result of interactions between the CNDs and the perovskite, the presence of the nonvolatile CND additive increases the power conversion efficiency (PCE) of the PSC from 14.48% ± 0.39% to 16.47% ± 0.26%. Furthermore, adding urea, a Lewis base, increases the PCE to 20.2%-the re...

Research efforts on achieving low interfacial density of states (Dit) as well as low electrical leakage currents on GaAs-based III–V compound semiconductors are reviewed. Emphasis is placed on ultra high vacuum (UHV) deposited Ga2O3(Gd2O3) and atomic layer deposition (ALD)-Al2O3 on GaAs and InGaAs. Ga2O3(Gd2O3), the novel oxide, which was electron-beam evaporated from a gallium-gadolinium-garnet target, has, for the first time, unpinned the Fermi level of the oxide/GaAs heterostructures. Interfacial chemical properties and band parameters of valence band offsets and conduction band offsets in the oxides/III–V heterostructures are studied and determined using X-ray photoelectron spectroscopy and electrical leakage transport measurements. The mechanism of III–V surface passivation is discussed. The mechanism of Fermi-level unpinning in ALD-Al2O3ex-situ deposited on InGaAs were studied and unveiled. Systematic heat treatments under various gases and temperatures were studied to achieve low leakage currents of 10-8–10-9 A/cm2 and low Dit's in the range of (4–9)×1010 cm-2 eV-1 for Ga2O3(Gd2O3) on InGaAs. By removing moisture from the oxide, thermodynamic stability of the Ga2O3(Gd2O3)/GaAs heterostructures was achieved with high temperature annealing, which is needed for fabricating inversion-channel metal–oxide–semiconductor filed-effect transistors (MOSFET's). The oxide remains amorphous and the interface remains intact with atomic smoothness and sharpness. Device performances of inversion-channel and depletion-mode III–V MOSFET's are reviewed, again with emphasis on the devices using Ga2O3(Gd2O3) as the gate dielectric.

In this study, we synthesized four acceptor–donor–acceptor type hole-transporting materials (HTMs) of SY1–SY4 for an HTMs/interfacial layer with carbazole as the core moiety and ester/amide as the acceptor unit. These HTMs contain 4-hexyloxyphenyl substituents on the carbazole N atom, with extended π-conjugation achieved through phenylene and thiophene units at the 3,6-positions of the carbazole. When using amide-based HTMs SY2 as a dopant-free HTM in a p–i–n perovskite solar cell (PSC), we achieved a power conversion efficiency (PCE) of 13.59% under AM 1.5G conditions (100 mW cm–2); this PCE was comparable with that obtained when using PEDOT:PSS as the HTM (12.33%). Amide-based SY2 and SY4 HTMs showed a larger perovskite grain than SY1 and SY3 because of the passivation of traps/defects at the grain boundaries and stronger interaction with the perovskite layer. In further investigation, we demonstrated highly efficient and stable PSCs when using the dopant-free p–i–n device structure indium tin oxide/NiO x /interfacial layer (SY-HTMs)/perovskite/PC61BM/BCP/Ag. The interfacial layer improved the PCEs and large grain size (micrometer scale) of the perovskite layer because of defect passivation and interface modification; the amide group exhibited a Lewis base adduct property coordinated to Ni and Pb ions in NiO x and perovskite, bifacial defect passivation and reduced the grain boundaries to improve the crystallinity of the perovskite. The amide-based SY2 exhibited the stronger interaction with the perovskite layer than that of ester-based SY1, which is related to the observations in X-ray absorption near edge structure (XANES). The best performance of the NiO x /SY2 device was characterized by a short-circuit current density (J sc) of 21.76 mA cm–2, an open-circuit voltage (V oc) of 1.102 V, and a fill factor of 79.1%, corresponding to an overall PCE of 18.96%. The stability test of the PCE of the NiO x /SY2 PSC device PCE showed a decay of only 5.01% after 168 h; it retained 92.01% of its original PCE after 1000 h in Ar atmosphere. Time-resolved photoluminescence spectra of the perovskite films suggested that the hole extraction capabilities of the NiO x /SY-HTMs were better than that of the bare NiO x . The superior film morphologies of the NiO x /SY-HTMs were responsible for the performances of their devices being comparable with those of bare NiO x -based PSCs. The photophysical properties of the HTMs were analyzed through time-dependent density functional theory with the B3LYP functional.