We report the enhanced photovoltaic properties in polycrystalline BiFeO3 (BFO) thin films with graphene as top electrodes. The short circuit current density (Jsc) and open circuit voltage of the heterojunction are measured to be 25 μA/cm2 and 0.44 V, respectively, much higher than the reported values for polycrystalline BFO with indium tin oxide (ITO) as top electrodes. Influence of HNO3 treatment on the photovoltaic properties is studied, and a significant photocurrent density improvement from 25 μA/cm2 to 2.8 mA/cm2 is observed. A metal-intrinsic semiconductor-metal model is proposed to explain the graphene induced enhancement comparing with traditional ITO.

Graphene-on-silicon Schottky junction solar cells were prepared with pillar-array-patterned silicon substrate. Such patterned substrate showed an anti-reflective characteristic and led to an absorption enhancement of the solar cell, which showed enhanced performance with short-circuit current density, open-circuit voltage, fill factor, and energy conversion efficiency of 464.86 mV, 14.58 mA/cm 2 , 0.29, and 1.96%, respectively. Nitric acid was used to dope graphene film and the cell performance showed a great improvement with efficiency increasing to 3.55%. This is due to the p-type chemical doping effect of HNO 3 which increases the work function and the carrier density of graphene. V

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BiFeO 3 / Bi 3.15 Nd 0.85 Ti 3 O 12 (BFO/BNdT) multilayer films have been grown on Pt-coated silicon substrate by chemical solution deposition. Using Bi3.15Nd0.85Ti3O12 as an inducing layer, ferroelectric properties of BiFeO3 were enhanced significantly. The 2Pr and coercive electric field of the Pt/BFO/BNdT/Pt capacitor were about 22.1 μC/cm2 and 50 kV/cm, respectively. The dielectric constant and the dissipation factor of the multilayer were 373 and 0.05 measured at 105 Hz, respectively. The multilayer capacitors not only exhibited excellent fatigue resistance without polarization reduction after 1010 switching cycles but also showed lower leakage current density (around the order of 10−9–10−7 A/cm2) and negligible data loss due to imprint. The magnetic hysteresis indicated that the multiplayer was antiferromagnetic and the saturated magnetization was about 2.47 emu/cm3.

Electrical and thermal properties of a carbon nanotube (CNT)/multiferroic BiFeO(3) (BFO)/Pt photovoltaic heterojunction are investigated for the first time. Enhanced photovoltaic properties (J(sc)≈ 2.1 μA cm(-2) and V(oc)≈ 0.47 V), as compared to the traditional polycrystalline BFO with indium tin oxide (ITO) as the top electrode, are observed due to the unique properties of CNT. An equivalent electrical and thermal model is constructed based on the energy band diagram of the CNT/BFO/Pt heterojunction for the first time and the carriers' transportation behavior is depicted theoretically. The influence of CdSe quantum dots (QDs) sensitization on the photovoltaic properties is presented, and a clear improvement of ~4 fold in photocurrent density is observed.

We report on the enhancement of photovoltaic performance in a graphene/polycrystalline BiFeO3 (BFO)/Pt heterojunction for the first time. The unique properties of the graphene electrode lead to a short circuit current density of 61 μA/cm2 and an open circuit voltage of 0.52 V in the heterojunction. These values are much higher than the results reported in polycrystalline BFO with indium tin oxide as the top electrode. A theoretical band diagram model and an equivalent electrical model considering the ferroelectric polarization, interface states, and energy band bending effect are constructed to depict the carrier transport behavior. Important photovoltaic parameters, such as conversion efficiency, illumination intensity response, ON/OFF characteristics, minority carrier lifetime, and external quantum efficiency, are investigated experimentally and theoretically. To improve the photovoltaic performance of the graphene/polycrystalline BFO/Pt heterojunction, HNO3 treatment, and CdSe quantum dots (QDs) filling/sensitizing, as two independent chemical and physical routines, were processed and compared. It can be seen that the photocurrent density exhibits a significant improvement from 61 μA/cm2 to 8.67 mA/cm2 (∼150 fold) after HNO3 treatment, while a considerable enhancement of ∼5 fold is seen with QDs filling/sensitizing. We also present and investigate an optical application of our graphene/polycrystalline BFO/Pt heterojunction as a photosensitive detector.

In this paper, nonvolatile bipolar resistive memory effects were observed in nitrogen doped diamond-like carbon (DLC) thin films prepared by a pulsed laser deposition technique. It is observed that the fabricated Pt/Ti/DLC/Pt structure exhibits good memory performances with an ON/OFF ratio >10, data retention time >104 s, and low operation voltage (<1.5 V). The current mechanism is fitted by Ohmic and space charge limited conduction laws in low resistance state and high resistance state scenarios. The formation/rupture of metal filaments is due to the diffusion of the titanium ions.

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