Photo Response Research Articles

PH‐responsivity and photoconductivity for the organic mixed ionic electronic conductor of PANI/PSS composite films

AbstractThe influence of ionic‐electronic coupling on the electrical conductivity and the photoconductivity of organic mixed ionic electronic conductor (OMIECs) of polyaniline/poly (4‐styrene sulfonic acid) (PANI/PSS) composite films. PANI/PSS composite films are connected by blending the carbon atoms within the aromatic ring in PANI with sulfonate groups in PSS. The electrical conductivity of PANI/PSS composite film increases from to as the pH value increases from 3 to 9. The electrical conductivity of PANI/PSS composite films for all pH values increases continuously as the temperature increases. Additionally, the PANI/PSS composite films exhibit photo responses at UV light since the band structure can absorb the light in this region. The photoconductivity curves of PANI/PSS composite films for different pH values exhibit good consistency and repeatability. Modeling raising photoconductivity and decaying conductivity after light off leads us to understand the underlying physics of the ionic‐electronic coupling and other parameters on the photoconductivity of OMIECs, consequently building OMIEC devices for different photoconductivity applications.

Photoelectrochemical Properties of Chemical Bath Deposited CdNiSe Thin Films

The chemical bath deposition approach was used to prepare Cd1−xNixSe thin film photoelectrodes on a substrate made of stainless-steel plate. The constructed cell has the configuration: p-CdNiSe | NaOH (1M)+S (1M)+Na2S (1M) | C (graphite). Studying current-voltage characteristics in the dark, capacitance–voltage in the dark, barrier-height measurements, power output, photo response, and spectral response are all part of characterizing the photoelectrochemical cell of the photoelectrodes. For the composition of Cd0.7Ni0.3Se, the junction ideality factor was determined to be minimal. It was discovered that the flat band potential and barrierheight was 710 mV and 0.181 eV respectively. The power output characteristic reveals that, for composition x = 0.3, the short circuit current, open circuit voltage, conversion efficiency and fill factor are respectively, 161 μA/cm2, 260 mV, 0.64% and 48.11%. The greatest current recorded at 725 nm is displayed in the spectral response.

The Properties and Activity of TiO2-based Nanorods as an Anti-Fouling Agent and a Photocatalyst

The properties and activity of TiO2-based nanorods as an antifouling agent and a photocatalyst for the catalytic degradation of methylene blue (MB) have been investigated. A modification of TiO2 with SiO2 was first carried out to enlarge the surface area. In order to enhance the TiO­2 photo response to the visible light region, a further modification of TiO2-SiO2 (TS) composites with polyaniline (PANI) was also conducted. The nanorod TiO2 exhibited an anatase structure based on the diffraction patterns. The TEM images showed that some TiO2 molecules were attached around SiO2 with a random orientation. The TiO2-SiO2-PANI (TS-PANI) exhibited the largest specific surface area (SBET) of about 256.85 m2/g. The profile on the AFM images of the composites showed that the nano-roughness of the coatings was confirmed. The photocatalytic activity was evaluated through the decomposition of MB both on the powder and the coated composites. The photocatalytic activity on the coatings was verified due to further application as anti-fouling coatings involving photocatalytic mechanism. The decomposition of MB using TS-PANI powder and TS-PANI coating composites was 89.5% and 90.2 %, respectively, with the irradiation time on the coatings was 20 min longer. The anti-fouling activity through the photocatalytic mechanism and nano-roughness surface was confirmed by the inhibition of barnacle growth on the teakwood surface immersed for two months in the sea.

Illumination dependent electrical, photosensitivity and photodetectivity properties of Au/SiO2/n-Si structures: optoelectronic situations

Abstract This study aims to examine the electrical, photosensitivity (S), photo-response (R), and photo-detectivity (D*) properties of Au/SiO2/n-type Si structures under different illumination intensities. The illumination-dependent properties of the Au/SiO2/n-type Si structure with SiO2 interlayer were obtained using current–voltage (I-V) characteristics. The ideality factors (n) and barrier heights (Φbo) values of Au/SiO2/n-type Si structures were obtained and compared from forward and reverse bias current–voltage (I-V) measurements at room temperature. Also, barrier heights (Φbo) and series resistance (R S ) values obtained from Norde method were compared with the values obtained from TE theory. It was observed that ideality factor and barrier height values obtained from forward bias region are higher than the values reverse bias. This means that the linearity or rectification feature in the reverse bias region is better than the forward bias region. Furthermore, photodiode values such as photo response (R), photosensitivity (S) and photodetectivity (D*) of Au/SiO2/n type Si structures were also examined depending on the light intensity. Consequently, the experimental results showed that the increase in reverse current with increasing light indicates that the Au/SiO2/n-type Si structures can be used in semiconductor technology as a photodiode, detector or sensor.

UV to NIR Broadband Flexible Photodetector Based on Solution‐Processed MoS2/PDPP3T Inorganic–Organic Hybrid Heterostructures

AbstractMolybdenum disulfide (MoS2) is a 2D material with excellent electrical and optical properties, and developing a universal technology for the preparation of high‐performance MoS2‐based photodetector is extremely desirable. Here, a UV to NIR broadband flexible photodetector based on MoS2/(PDPP3T) inorganic–organic hybrid heterostructures is reported. In the experiment, high crystalline 2H‐phase few‐layer MoS2 nanoflakes are first prepared by optimized electrochemical intercalation of tetraheptylammonium cation (THA+) and ultrasound‐assisted exfoliation strategy. Thereafter, a narrow bandgap organic semiconductor PDPP3T is introduced to construct the MoS2/Poly(diketopyrrolopyrrolothiophrn) (PDPP3T) heterojunction. Experimental results reveal that the photodetector can have broadband photo response from 380 to 980 nm. Meanwhile, excellent responsivities and detectivity of 12.4 mA W−1, 2.2 × 1010 Jones at 380 nm and 0.1 mA W−1 and 5 × 108 Jones at 980 nm are achieved, which are ≈10 (UV band)/100 (NIR band) times high than that obtained on the pure MoS2‐based detector. Moreover, the flexibility of the device is investigated by conformal covering the device on a curved surface (R = 5 and 2.5 mm), it shows that the photo response remains almost the same as that measured on the planar substrate, indicating the possible application in the wearable electronics.

Solar enhanced oxygen evolution reaction with transition metal telluride.

The photo-enhanced electrocatalytic method of oxygen evolution reaction (OER) shows promise for enhancing the effectiveness of clear energy generation through water splitting by using renewable and sustainable source of energy. However, despite benefits of photoelectrocatalytic (PEC) water splitting, its uses are constrained by its low efficiency as a result of charge carrier recombination, a large overpotential, and sluggish reaction kinetics. Here, we illustrate that Nickel telluride (NiTe) synthesized by hydrothermal methods can function as an extremely effective photo-coupled electrochemical oxygen evolution reaction (POER) catalyst. In this study, NiTe was synthesized by hydrothermal method at 145°C within just an hour of reaction time. In dark conditions, the NiTe deposited on carbon cloth substrate shows a small oxygen evolution reaction overpotential (261mV) at a current density of 10mA cm-2, a reduced Tafel slope (65.4mV dec-1), and negligible activity decay after 12h of chronoamperometry. By virtue of its enhanced photo response, excellent light harvesting ability, and increased interfacial kinetics of charge separation, the NiTe electrode under simulated solar illumination displays exceptional photoelectrochemical performance exhibiting overpotential of 165mV at current density of 10mA cm-2, which is about 96mV less than on dark conditions. In addition, Density Functional Theory investigations have been carried out on the NiTe surface, the results of which demonstrated a greater adsorption energy for intermediate -OH on the catalyst site. Since the -OH adsorption on the catalyst site correlates to catalyst activation, it indicates the facile electrocatalytic activity of NiTe owing to favorable catalyst activation. DFT calculations also revealed the facile charge density redistribution following intermediate -OH adsorption on the NiTe surface. This work demonstrates that arrays of NiTe elongated nanostructure are a promising option for both electrochemical and photoelectrocatalytic water oxidation and offers broad suggestions for developing effective PEC devices.

Role of metal (Fe(III), Zn(II), and Co(III)) and porphyrin in enhancing photocatalytic performance of MTCPP/TiO2 photocatalysts

Metal-porphyrin complexes modified TiO2 photocatalyst, called MTCPP@P25, shows excellent photocatalytic activity under visible light irradiation. Metal-porphyrin is successfully utilized to broaden the photo response range of TiO2 from ultraviolet (3.2 eV) to visible light (2.43 eV to 2.65 eV) resulting in significant enhancement of photocatalytic efficiency. MTCPP@P25 exhibited the higher photocatalytic activity than bare TiO2. Additionally, introduction of different metals, like Fe, Zn, and Co into porphyrin ring can effectively adjust the photocatalytic activity of MTCPP@P25 due to the increasing the electron density of porphyrin rings. The degradation order for MB followed as FeTCPP@P25≧ZnTCPP@P25 > CoTCPP@P25. This finding demonstrated that FeTCPP@P25 and ZnTCPP@P25 possess higher photo-excited electrons under visible irradiation resulting in higher photocatalytic performance. Based on the PL and EIS analysis, FeTCPP@P25 exhibited longest lifetime and fast electron transition compared to ZnTCPP@P25. The spent FeTCPP@P25 were reusable after three cycles, the efficiency remained at approximately 80 %.

Generalized and robust model for GAN-generated image detection

Generative adversarial network (GAN)-generated image detection is a crucial yet challenging problem. The advancement of diverse generative models makes it simpler to build realistic synthetic images, but it also increases the likelihood of using images maliciously. Recent techniques of fake image detection often overfit to specific GANs, incapable of generalizing to other GANs. Each GAN leaves its distinct fingerprint on the images it generates. We propose a simple and compact attention network that exploits high-frequency and noise residual patterns of images. We design two-channel image representations in the preprocessing phase, with one channel using a bilateral high pass filter (BiHPF) for high-frequency patterns and the other using photo response non-uniformity (PRNU) for noise residuals capturing from GAN-generated and real images. The feature maps pass through the attention network with a dense layer for classification tasks. We assess the generalizability and robustness of the model through extensive experiments. The model is evaluated on a benchmark dataset in various settings, including cross-category, cross-GAN models with varying class settings and different color manipulations. This study demonstrates that the proposed model outperforms state-of-the-art (SOTA) methods by approximately 5% in different experiment settings.

Influence of deposition temperature on the defect mediated persistence photo-conducting behaviour of spray coated Zn0.96Nd0.04O thin films

The incorporation of Neodymium into ZnO lattice enhances the photo conducting property of the deposited films which are strongly dependent on preparation conditions. Hence, the comprehensive work carried out to understand the influence of deposition temperature (300 °C–500 °C) on the persistence photoconductivity of Zn0.96Nd0.04O films deposited on glass substrates using spray pyrolysis method. The maximum crystallite size of ∼16.3 nm with minimum dislocation density and strain values were noticed for the films deposited at 450 °C. The mixed fibrous -granular morphology was noticed in the deposited films. The maximum transparency above 90 % in the visible region and an increased bandgap of 3.42 eV was observed in the films deposited at 450 °C. The percentage of defects were calculated using the area under the curve of photoluminescence spectra. The charge carrier density of 1.7 × 1017 cm−3, mobility of 62.8 cm2/Vs and lesser resistivity of 1.3 × 102 Ω cm were noted for the films deposited at 450 °C. Under the illumination of UV light, the photocurrent of Zn0.96Nd0.04O films deposited at 450 °C increased by four orders. The persistence in the photo resistance was due to the presence of Zn and O related defects, which acts as trap centres. The variation of photo resistance with time indicates the films deposited at 450 °C has faster photo response due to the faster electron – hole recombination process. The maximum photocurrent at 360 nm was noted for the films synthesized at 450 °C due to improved crystallinity with stoichiometry nature of the films. Hence, the Zn0.96Nd0.04O films deposited at 450 °C suitable for light dependent resistor and fixed wavelength UV photodetector applications.

Double-weighted photo response non-uniformity extraction model based on multi-scale neighborhood shrinkage and structural filtering for YouTube compressed videos

Double-weighted photo response non-uniformity extraction model based on multi-scale neighborhood shrinkage and structural filtering for YouTube compressed videos

Engineering surface state density of monolayer CVD grown 2D MoS2 for enhanced photodetector performance.

This study demonstrates the effect of nitrogen doping on the surface state densities (Nss) of monolayer MoS2 and its effect on the responsivity and the response time of the photodetector. Our experimental results shows that by doping monolayer MoS2 by nitrogen, the surface state (Nss) increases thereby increasing responsivity. The mathematical model included in the paper supports the relation of photocurrent gain and its dependency on trap level which states that the increasing the trap density increases the photocurrent gain and the same is observed experimentally. The experimental results at room temperature revealed that nitrogen doped MoS2 have a high NSS of 1.63 X 1013 states/m2/eV compared to undoped MoS2 of 4.2 x 1012 states/m2/eV. The increase in Nss in turn is the cause for rise in trap states which eventually increases the value of photo responsivity from 65.12 A/W (undoped MoS2) to 606.3 A/W (nitrogen doped MoS2). The response time calculated for undoped MoS2 was 0.85 sec and for doped MoS2 was 0.35 sec. Finally, to verify the dependence of surface states on the responsivity, the surface states were varied by varying temperature and it was observed that upon increment in temperature, the surface states decreases which causes the responsivity values also to decrease.

N‐Type GaSe Thin Flake for Field Effect Transistor, Photodetector, and Optoelectronic Memory

AbstractThe family of 2D chalcogenide semiconductors has been growing rapidly. Metal monochalcogenides, for instance, can enable new possibilities in functional electronics and optoelectronics. A Gallium Selenide (GaSe) thin flake is used to fabricate a back gated field effect transistor (FET) with n‐type conduction behavior and wide hysteresis at the ambient conditions. The device shows high mobility up to 28 cm2 V−1 s−1 with Ion/Ioff ratio over 103. Under the laser exposure, the device shows a decrease in the threshold voltage and a left‐shift of the transfer characteristic with a slight increase in the current. The transfer characteristic exhibits a hysteretic behavior with hysteresis width linearly dependent on the applied gate voltage. Moreover, the GaSe‐based FET shows a photo response with a photoresponsivity of 475 mAW−1 and detectivity of 4.6 × 1012 Jones. The photocurrent rise and decay times are 0.1 and 1.3 s, respectively. Furthermore, the GaSe FET device can be used as a performant memory device with well separated states and memory window enhanced by the laser exposure, confirming an optoelectronic memory class.

Near‐Infrared Active Tri‐nanohybrid for Enhanced Energy Harvesting

AbstractEfficient energy harvesting through full solar spectrum utilization has been considered a promising solution to world energy and environmental issues. In this direction, lead sulphide (PbS) quantum dot (QD) based hybrid materials find greater application due to their near‐infrared (NIR) active photo response. Slower charge injection and inefficient charge separation limit photoactive response of such NIR active low band gap semiconductor like PbS QDs. Moreover, constructing dual charge transfer pathways in a PbS QDs based nanocomposite through the formation of hybrids with suitable materials can be advantageous in suppressing the charge recombination. In this work, we have synthesized a nanocomposite after decorating the PbS‐QDs with semiconducting TiO2 nanoparticles modified with multiwall carbon nanotubes (MWCNT) and thus forming the tri‐hybrid (PbS‐TiO2‐MWCNT) nanocomposites. The enhanced photo‐activities of the tri‐hybrid, as compared to di‐hybrids like PbS‐TiO2, PbS‐MWCNT were confirmed by the steady state, time‐resolved photoluminescence (TRPL) measurements and reactive oxygen species (ROS) generation measurements. Higher ROS generation in the tri‐hybrid has been correlated with a faster interfacial electron transfer due to the dual charge injection pathway of PbS QD to TiO2 and MWCNT. The enhanced activity of the trio‐hybrid has also been analyzed from the first principal calculations in light of an efficient interfacial electron transfer as a result of the dual charge injection pathway. The photoelectrochemical water‐spilling response of the photoanodes in terms of photocurrent density, electrochemical impedance, and Mott–Schottky measurements on PbS‐TiO2 and PbS‐TiO2‐MWCNT photoanodes reveal that a combination of MWCNT and TiO2 exhibits an increase in electrical double layer capacitance, decrease in series resistance and enhancement of carrier density with NIR illumination at the heterojunction. Overall, all the dynamical studies at the interface of the trihybrid‐based photoanodes demonstrate its potential of utilization as a futuristic NIR‐ active photoelectrochemical water‐splitting material.

Ternary organic bulk-heterojunction strategy enables efficient light utilization for perovskite solar cells

Extending the photoresponse into the near-infrared region (NIR) is an urgent research topic in perovskite solar cells. A ternary bulk heterojunction (BHJ) layer composited with PC61BM, D18-Cl and Y6 was deposited onto the perovskite to broaden light absorption. The ternary BHJ layer can absorb low-energy photons in the NIR region (800–920 nm) and generate excitons. Subsequently, these excitons dissociate into free electrons and holes at the donor-acceptor interface, thus extending the device's photo response up to 920 nm. Moreover, due to the good electron transport capabilities of the acceptors Y6 and PC61BM in the BHJ film, the BHJ layer also acts as the electron transport layer in the inverted PSC device. The inverted P–I–N device based on perovskite/BHJ achieved an external quantum efficiency (EQE) up to 30% in the near-infrared range. Compared to control PSCs, the short-circuit current (JSC) increased from 21.64 to 24.35 mA cm−2, resulting in a high PCE of 19.88%. Additionally, the high hydrophobic surface of the ternary layer contributes to the good long-term stability of the device. The results demonstrate that the ternary organic bulk heterojunction is an effective strategy for achieving efficient light utilization in the near-infrared region and enhancing power conversion efficiency in perovskite solar cells.

Photoelectrical characterization of heavily doped p-SiC Schottky contacts

The availability of photoelectrical characterizations of heavily Al-doped p-SiC Schottky contacts was clarified. We conducted a systematic study of four samples with different Al doping concentrations from 1 × 1018 to 5 × 1019 cm−3. Although the current–voltage (I–V) characteristics had lost rectification, reasonable Schottky barrier height (qϕ B) values were obtained up to 1 × 1019 cm−3 by capacitance voltage, photo response, and scanning internal photoemission microscopy (SIPM) measurements. In the two-dimensional characterization by SIPM, large photocurrent spots corresponding with low qϕ B were observed in an average density of 103 to 104 cm−2. However, except for these spots, a high uniformity of about 2 meV standard deviation was obtained for qϕ B over the entire observed electrodes. These results indicate that SIPM is able to characterize the inhomogeneity of heavily doped p-SiC contacts with very leaky I–V characteristics.

The impact of sputtering pressure on the TiO2/p-Si interface and its implications for hole-blocking and photodetection

One convenient approach to minimize the surface recombination loss in Si is to passivate the surface dangling bonds by depositing a thin TiO2 layer on the bulk Si. Besides, the p-Si/TiO2 interface can initiate hole-blocking and facilitate efficient electron transport through the TiO2 layer; thereby, promoting the extraction of electrons for efficient onward utilization. In this context, the current investigation involves studying how the Ti3+ donor states, produced by deliberately introducing O-vacancies controlled by changing the plasma pressure in the RF-magnetron sputtering chamber during the growth of the TiO2 thin films, can change the material's Fermi level and work function and modify the band bending and band offset as well as the fixed oxide charge density in the p-Si/TiO2 heterojunction interface. The TiO2/p-Si interface has been studied through capacitance-voltage (C-V) analysis to determine the interface parameters such as fixed oxide charge, the density of interface traps, and the dielectric constant of TiO2. The studied hole-blocking property of the interface has been correlated to the photoresponsivity of the metal-oxide-semiconductor (MOS) structure. The MOS device fabricated at a pressure of 30 mTorr displays a large saturation current (15.95 μA cm–2) when subjected to a positive gate bias, facilitated by the relatively low conduction band offset (ΔEC ∼0.20 eV), significant positive fixed oxide charge (+1.18 ×1011 cm–2) and the interface trap density (1.03 ×1012 cm–2), which enhanced the transport of minority carrier electrons from the p-Si to the metal, resulting in a good photo responsivity ∼0.158 AW–1 and photo gain of ∼37.5 under white light illumination. Optimum hole-blocking and surface passivation characteristics of the TiO2/p-Si interface together may facilitate fabricating improved heterojunction Si solar cells.

Synergistic Engineering of Top Gate Stack for Low Hysteresis 2D MoS2 Transistors

Abstract2D semiconductors have emerged as candidates for next‐generation electronics. However, previously reported 2D transistors which typically employ the gate‐first process to fabricate a back‐gate (BG) configuration while neglecting the thorough impact on the dielectric capping layer, are severely constrained in large‐scale manufacturing and compatibility with complementary metal–oxide–semiconductor (CMOS) technology. In this study, dual‐gate (DG) field‐effect transistors have been realized based on wafer‐scale monolayer MoS2 and the gate‐last processing, which avoids the transfer process and utilizes an optimized top‐gate (TG) dielectric stack, rendering it highly compatible with CMOS technology. Subsequently, the physical mechanism of TG dielectric deposition and the corresponding controllable threshold voltage (VTH) shift is investigated. Then the fabricated TG‐devices with a large on/off ratio up to 1.7 × 109, negligible hysteresis (≈14 mV), and favorable stability. Additionally, encapsulated TG structured photodetectors have been demonstrated which exhibit photo responsivity (R) up to 9.39 × 103 A W−1 and detectivity (D*) ≈2.13 × 1013 Jones. The result paves the way for future CMOS‐compatible integration of 2D semiconductors for complex multifunctional IC applications.

Investigation of Passivation Pretreatment Processes for Mid‐/Long‐Wavelength Dual‐Band Infrared Focal Plane Arrays Based on Type‐II InAs/GaSb Superlattices

Herein, through the analysis of devices with different passivation pretreatment processes, it is found that after surface corrosion, the optimized process of O3 treatment combined with hydrochloric acid and H3PO4/C6H8O7/H2O2/H2O treatments can significantly improve the electrical performance of the device. By analyzing the curves of dark current density varying with temperature of the mid‐wavelength (MW) and long‐wavelength (LW) dual‐color devices, it is verified that there are three leakage mechanisms in the device: diffusion current, trap‐assisted tunneling current, and generation–recombination current. Finally, a 640 × 512 MW/LW dual‐color superlattice infrared detector is fabricated with a pixel pitch of 20 μm. The cutoff wavelength of the MW channel is 5.04 μm. The cutoff wavelength of the LW channel is 9.51 μm. The noise equivalent temperature difference of MW is 16.5 mK and LW is 35.1 mK. The photoresponse nonuniformity is 6.21% for MW and 10.51% for LW. The blind pixel rate is 0.66% for MW and 8.56% for LW. The imaging demonstration is completed. The research has laid the foundation for the engineering application of dual‐color infrared detectors.

Video source camera identification using fusion of texture features and noise fingerprint

In Video forensics, the objective of Source Camera Identification (SCI) is to identify and verify the origin of a video that is under investigation. This aids the investigator to trace the video to its owner or narrow down the search space for identifying the offender. Nowadays, it is easy to record and share videos via internet or social media with smartphones. The availability of sophisticated video editing tools and software allow offenders to modify video's context. Thus, identifying the right source camera that was used to capture the video becomes complicated and strenuous. Existing methods based on video metadata information are no longer reliable as it could be modified or stripped off. Better forensic procedures are therefore required to prove the authenticity and integrity of the video that will be used as evidence in court of law. Certain inherent camera sensor properties such as, subtle traces of Photo Response Non-Uniformity (PRNU) are present in all captured videos due to unnoticeable defect during the manufacture of camera's sensor. These properties are used in SCI to classify devices or models as they are unique. In this work, we focus on SCI from videos or Video Source Camera Identification (VSCI) to verify the authenticity of videos. PRNU can be affected by highly textured content or post-processing when computed from a set of flat field images. To mitigate these effects, Higher Order Wavelet Statistics (HOWS) information from PRNU of a video I-frame is combined with information from two other texture features i.e., Local Binary Pattern (LBP) and Gray Level Co-occurrence Matrix (GLCM). The extracted feature vector is fused via concatenation and fed to Support Vector Machine (SVM) classifier to perform training and testing for VSCI. Experimental evaluation of our proposed method on videos from different publicly available datasets show the effectiveness of our method in terms of accuracy, resource efficiency, and complexity.

Sm, Nd doped BiFeO3 epitaxial film for photodetector with extremely large on–off current ratio

BiFeO3 is one of the star materials in the field of ferroelectric photovoltaic for its relatively narrow bandgap (2.2–2.7 eV) and better visible light absorption. However, a high temperature over 600 °C is indispensable in the usual BiFeO3 growth process, which may lead to impure phase, interdiffusion of components near the interface, oxygen vacancy and ferrous iron ions, which will result in large leakage current and greatly aggravate the ferroelectricity and photoelectric response. Here we prepared Sm, Nd doped epitaxial BiFeO3 film via a rapid microwave assisted hydrothermal process at low temperature. The Bi0.9Sm0.5Nd0.5FeO3 film exhibits narrow bandgap (1.35 eV) and photo response to red light, the on–off current ratio reaches over 105. The decrease in band gap and +2/+3 variable element doping are responsible for the excellent photo response. The excellent photo response performances are much better than any previously reported BiFeO3 films, which has great potential for applications in photodetection, ferroelectric photovoltaic and optoelectronic devices.