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Carbon nanospheres are successfully synthesized with a particle size of about 140 nm using a two‐step hydrothermal method and used the carbon nanospheres as the deposition template material on the surface of P25(TiO2) by means of vertical deposition method. The antiopaline TiO2 photonic crystal (PC) structure is further prepared via immersed carbon nanospheres in TiO2 precursor solution, and the antiopal PC is used as the scattering layer of the photoanode of dye‐sensitized solar cell (DSSCs). As a comparison, the antiopal PC reflective layer is also prepared on the photoanode of DSSCs using polystyrene nanospheres as the template material. The photoanodes with those PC scattering layers prepared with different template materials are fabricated into complete DSSCs. The final photoelectric conversion efficiency of the DSSCs prepared with carbon nanospheres as the template material reaches 7.02%, which is comparable to the cells prepared with polystyrene nanospheres as the template material. The efficiency of the cell with the scattering layer is increased by about 16% compared with that of the normal DSSC based on P25. [ABSTRACT FROM AUTHOR]

The Clarion-Clipperton Zone (CCZ) is a 4 million km2 area in the eastern Central Pacific Ocean exhibiting large variability in environmental parameters, particularly oxygen and primary production, that is being targeted for deep-sea polymetallic nodule mining. This remote region’s pelagic biology is very poorly sampled, including for micronekton and zooplankton that provide essential ecosystem services such as carbon flux and support for commercial fisheries. We built a baseline of deep scattering layer (DSL) depths and vertical migration behaviors, proxies for mesopelagic micronekton and zooplankton communities, using shipboard acoustic Doppler current profiler datasets. Acoustic data (38 kHz, 75 kHz) were compiled from research cruises passing near or through the CCZ (2004–2019), and environmental data (mean midwater oxygen partial pressure, surface chlorophyll-a, and sea surface height anomaly) were assembled from the World Ocean Atlas and satellite oceanographic datasets. Our results suggest that midwater oxygen, associated with the Eastern Tropical Pacific Oxygen Minimum Zone (OMZ), is the strongest predictor of daytime DSL depths and the proportions of midwater populations that undergo vertical migration in this region. We used these relationships to predict micronekton and zooplankton behaviors across the CCZ, including licensed mining exploration areas and no-mining reserves. While the OMZ encompasses most licensed exploration areas, the current network of reserves lies outside of the core OMZ and ultimately may not represent or protect the pelagic OMZ fauna at highest risk from mining impacts. This research will further assist in developing resource exploitation regulations by the International Seabed Authority, and will provide mesopelagic baseline information for monitoring changes that may occur in the CCZ once industrial-scale mining begins.

Krill play a crucial role in the transfer of energy in the marine food web, connecting primary producers and the upper trophic levels in the Terra Nova Bay polynya (TNBP), which is part of the Ross Sea marine protected area. Despite the substantial ecological importance of krill, there are few studies on their distribution and abundance in the TNBP. An acoustic survey was conducted on 7–14 January 2019 in the TNBP, Ross Sea, using a Simrad EK60 echosounder (38 and 120 kHz) aboard the icebreaker RV Araon. The most commonly used range of the difference of the mean volume backscattering strength (MVBS) (2–16 dB) was applied to distinguish krill. The acoustic data (120 kHz) were extracted to examine the krill distribution characteristics. The study area was divided into low-value areas and high-value areas based on the third quartile of the nautical area scattering coefficient. The results showed that the krill aggregations were distributed in three layers at depths of 0–30 m, 70–110 m, and 270–300 m. The interpolated environmental parameters associated with the backscattering strength were compared. High-value areas of krill coincided with relatively low temperature, low salinity, and high chlorophyll, although very weak correlations were found. The primary goal of this study was to understand the vertical and horizontal distributions of krill acoustic biomass and to relate the observed patterns to the dominant environmental conditions.

During the North Atlantic Aerosols and Marine Ecosystems Study in the western North Atlantic, float‐based profiles of fluorescent dissolved organic matter and backscattering exhibited distinct spike layers at ∼ 300 m. The locations of the spikes were at depths similar or shallower to where a ship‐based scientific echo sounder identified layers of acoustic backscatter, an Underwater Vision Profiler detected elevated concentration of zooplankton, and mesopelagic fish were sampled by a mesopelagic net tow. The collocation of spike layers in bio‐optical properties with mesopelagic organisms suggests that some can be detected with float‐based bio‐optical sensors. This opens the door to the investigation of such aggregations/layers in observations collected by the global biogeochemical‐Argo array allowing the detection of mesopelagic organisms in remote locations of the open ocean under‐sampled by traditional methods. Plain Language Summary: The largest migration on Earth happens daily when animals migrate to feed on phytoplankton at the surface. They return to the twilight zone at night likely to hide from visual predators. These migrating organisms—zooplankton, fish, squids, and jellyfish—are well studied in some parts of the world's oceans, but their study is limited to the spatial and temporal coverage of ships. At the same time, a network of robots profiling the ocean from the surface to 2,000 m continuously measures the properties of the water at hundreds of locations daily, but so far, they have not been used for detecting migrating organisms. In this study, we show that migrating organisms can be attracted to emitted light by sensors mounted on the profiling robots and produce anomalous signals that can be used to suggest their presence. This method will help study those animals over extended time scales and in remote areas not easily accessible by ships. In addition, it will improve our interpretation of the profiling robots' measurements. Incorporating recently developed instruments, such as underwater cameras, with existing optical sensors could help study some of those organisms living deep in the ocean's interior. Key Points: We present concurrent observations of mesopelagic organisms with echo sounders, a camera, a net tow, and profiling floatsLayers of mesopelagic organisms coincide with distinct spike layers in fluorescence and backscattering profilesNovel application of biogeochemical‐Argo float enables the detection of mesopelagic organisms and their migration [ABSTRACT FROM AUTHOR]

• DVMs above seamount slopes and in open-waters, but no clear pattern over plateaus. • Intense nighttime DSLs in open-waters but not over seamount slopes. • Spatial structure of SSLs and DSLs varied between diel periods and regions. • Differences in SSLs suggest existence of seamount associated micronekton community. • Seamounts influenced the spatial dynamics of SSLs and DSLs. We examined the diel vertical migration (DVM) behavior and vertical spatial structure of sound-scattering layers (SLs) at two seamounts (Condor and Gigante) in the Azores and in surrounding open-waters. Active acoustic data were recorded day and night during nine cruises conducted in spring, summer and autumn between 2009 and 2011. SLs were permanent features with two main layers, shallow scattering layers (SSLs) and deep scattering layers (DSLs). Over seamount plateaus, SSLs aggregated close to the seafloor during the day and in slightly shallower waters at night. Backscatter intensity on plateaus varied little between day and night and was consistently higher than in SSLs above slopes or in open-waters. DSLs found over slopes and open-waters migrated towards the surface at dusk and returned to their daylight depths at dawn but an intense DSL persisted overnight in deep open-waters. Variograms showed that SSLs and DSLs were not uniformly distributed but amount of spatial heterogeneity varied between seamount plateaus, slopes and open-waters, and day-night periods. Taken together, these findings suggest that (1) Condor and Gigante Seamounts host a resident micronekton community, (2) there is an influx of vertically migrating organisms over the plateaus at night, and (3) seamount topography affects the DVM behavior of the DSL. Physical processes, such as Taylor cap effect, along with topographic blockage and lateral advection of migrating organisms, may play a role in transporting micronekton from open-waters to seamount plateaus. These findings are critical to understanding the ecology of seamount communities and the function of seamount habitats in oceanic ecosystems. [ABSTRACT FROM AUTHOR]

The study of marine organism behaviour and vertical distribution requires the use of techniques that do not disturb their natural state. This study analyses the mesopelagic fishes behaviour influenced by the presence of a research vessel. Acoustic data recorded on board the RV "Ángeles Alvariño" during the RAPROCAN 2017 survey showed a clear pattern of mesopelagic fishes migrating deeper in the water column at night when the DP system was connected. Details on how the scatterers changed their trajectory when migrating to the surface at night and the progressive increase in avoidance depth when dawn approached is shown. An experiment was carried out to discern fish reaction to vessel lights and to the DP system. While a dispersed diving was detected when the lights were switched on, a more acute reaction to the DP system was registered with not only vertical displacement, but also an increment in scattering produced by an aggregating behaviour. Both vessel DP-noise and light modify the mesopelagic fish behaviour, which needs to be accounted for when studying mesopelagic layers close to the surface. Surveys aiming at estimating abundance and biomass from these species are encouraged to do so at day time. [ABSTRACT FROM AUTHOR]

Micronekton organisms are a central component of the trophic organization in the pelagic ecosystem, being prey to top predators and participating in the export of carbon from the surface to the deep layers. Despite their importance, the abundance estimates and species distribution of micronekton remain largely uncertain. This study aimed to compare and assess two sampling methods classically used for the estimation of micronekton abundance in mesopelagic acoustic scattering layers: scientific echosounder and trawl sampling. Measurements of 38 and 70 kHz hull-mounted echosounders were examined with biological trawl samples from 8 surveys in the South-West tropical Pacific. A model of acoustic observation was built from the trawl sampling species composition and forward scattering models. Predicted and observed acoustic responses are compared to assess the variability and the difference between the acoustic and trawl sampling methods in various scattering layers, for day and night periods. The difference between methods decreased with depth and with increasing abundance of fish with swimbladders caught in trawls. Notably, this difference was found to be minimal in the nocturnal deep scattering layer (mesopelagic zone, depth>200 m). This study emphasizes potential lower estimates of organisms' abundance by trawling and a bias towards mesopelagic fish. Understanding the differences between methods and their variability within different scattering layers is essential for studying micronekton and improving the precision of biomass estimates. • Acoustic-trawl surveys in scattering layers of West tropical Pacific. • Forward scattering models applied to micronekton trawl sampling with a high species diversity. • The difference in micronekton density estimates between acoustic and trawl methods varies across scattering layers. • The disparities between methods decrease in night mesopelagic layers and trawls with high swimbladdered fish density. [ABSTRACT FROM AUTHOR]

Natural seepage of methane into the oceans is considerable, and plays a role in the global carbon cycle. Estimating the amount of this greenhouse gas entering the water column is important in order to understand their environmental impact. In addition, leakage from man-made structures such as gas pipelines may have environmental and economical consequences and should be promptly detected. Split beam echo sounders (SBES) detect hydroacoustic plumes due to the significant contrast in acoustic impedance between water and free gas. SBES are also powerful tools for plume characterization, with the ability to provide absolute acoustic measurements, estimate bubble trajectories, and capture the frequency dependent response of bubbles. However, under challenging conditions such as deep water and considerable background noise, it can be difficult to detect the presence of gas seepage from the acoustic imagery alone. The spatial coherence of the wavefield measured across the split beam sectors, quantified by the coherence factor (CF), is a computationally simple, easily available quantity which complements the acoustic imagery and may ease the ability to automatically or visually detect bubbles in the water column. We demonstrate the benefits of CF processing using SBES data from the Hudson Canyon, acquired using the Simrad EK80 SBES. We observe that hydroacoustic plumes appear more clearly defined and are easier to detect in the CF imagery than in the acoustic backscatter images. [ABSTRACT FROM AUTHOR]

Scattering structures, including deep (>200 m) scattering layers are common in most oceans, but have not previously been properly documented in the Arctic Ocean. In this work, we combine acoustic data for distribution and abundance estimation of zooplankton and fish with biological sampling from the region west and north of Svalbard, to examine high latitude meso- and epipelagic scattering layers and their biological constituents. Our results show that typically, there was strong patchy scattering in the upper part of the epipelagic zone ( 440 m) in the Arctic habitat north of Svalbard compared to those south in the Fram Strait west of Svalbard (WMD ~400 m). The surface integrated backscatter [Nautical Area-Scattering Coefficient, NASC, sA (m2 nmi−2)] was considerably lower in the waters around Svalbard compared to the more southern regions (62–69°N). Also, the integrated DSL nautical area scattering coefficient was a factor of ~6–10 lower around Svalbard compared to the areas in the south-eastern part of the Norwegian Sea ~62°30′N. The documented patterns and structures, particularly the DSL and its constituents, will be key reference points for understanding and quantifying future changes in the pelagic ecosystem at the entrance to the Arctic Ocean.

Shallow and deep scattering layers (SLs) were surveyed with split-beam echosounders across the southwest Indian Ocean (SWIO) to investigate their vertical and geographical distribution. Cluster analysis was employed to objectively classify vertical backscatter profiles. Correlations between backscatter and environmental covariates were modelled using generalized additive mixed models (GAMMs) with spatial error structures. Structurally distinct SL regimes were found across the Subantarctic Front. GAMMs indicated a close relationship between sea surface temperature and mean volume backscatter, with significantly elevated backscatter in the subtropical convergence zone. The heterogeneous distribution of scattering layer biota reflects the biogeographic zonation of the survey area and is likely to have implications for predator foraging and carbon cycling in the Indian Ocean. [ABSTRACT FROM AUTHOR]

We make a comparison of the mesopelagic sound scattering layers (SLs) in two contrasting optical environments; the clear Red Sea and in murkier coastal waters of Norway (Masfjorden). The depth distributions of the SL in Masfjorden are shallower and narrower than those of the Red Sea. This difference in depth distribution is consistent with the hypothesis that the organisms of the SL distribute according to similar light comfort zones (LCZ) in the two environments. Our study suggest that surface and underwater light measurements ranging more than 10 orders of magnitude is required to assess the controlling effects of light on SL structure and dynamics. [ABSTRACT FROM AUTHOR]

Efficient light extraction for organic light emitting diodes (OLED) using scalable processes and low-cost materials are important prerequisites for the future commercialization of OLED lighting devices. The light-extraction technology exhibited in this paper uses polymer-based high-refractive index scattering layers processed from solution. The scatter matrix formulation incorporates two types of nanoparticles for refractive index tuning and scattering, respectively. Planarization by the same material in order to reduce surface defects was critical for achieving highly increased device yield. Highly efficient and defect-free large-area (1.8 cm 2 ) white OLED devices were fabricated on top of the scattering layer in a bottom emitter configuration. Light extraction enhancement leads to an overall efficiency gain of up to 81% for luminances of 5000 cd m −2 . [ABSTRACT FROM AUTHOR]

Using the pre-treatment of the working photoelectrode and the admixture light-scattering layer can ameliorate the performance of TiO dye-sensitized solar cells (DSSCs). TiCl treatments on TiO electrodes improve the adhesion and mechanical strength of the TiO layer. The HNO treatment significantly enhances the dispersion of TiO particles and increases the surface area and porosity of TiO films. The scattering layer formed by admixing both nanometer-sized and submicron-sized TiO particles greatly enhances the DSSC performance. The light absorption is considerably better in TiO films with a mixture of large and small particles. This mixture is capable of efficient light-scattering while simultaneously providing a larger surface area for effective dye adsorption. Each of these technologies for the TiO film fabrication has a significant influence on the overall photovoltaic parameters of DSSCs, resulting in improvements in energy conversion performance. [ABSTRACT FROM AUTHOR]

The article presents a study that evaluates several behavioral patterns of the mesopelagic fish Maurolicus muelleri in Masfjorden, Norway through acoustical observations. The study is undertaken through the use of echograms where results are visualized through MATLAB and the measurement of salinity, dissolved oxygen, and temperature. The results of the study show several behavioral patterns of Maurolicus including midnight sinking between dusk and dawn, early morning ascents, and migration.

The article discusses a research study on mesopelagic fish Maurolicus muelleri and their seasonal and diurnal vertical distribution variations in following constant light intensity also called isolume. Researchers measured surface irradiance or photosynthetically active radiation (PAR) at 400 to 700 nanometers on Masfjorden, west coast of Norway from January to September 2008 and compared the acoustic observations of ontogenerically variation of scattering layers (SLs). Results showed maximum surface irradiance to be 12-15 time higher on sunny April and May days increasing until midday while SLs depth variations showed upper border logarithmic surface irradiance at 50 to 70 meters deep.

Abstract: We studied the possibility of photocurrent enhancement in Dye Solar Cells (DSCs) by means of two strategies of light management, namely the use of a scattering layer (SL) and the efficient coupling of incoming light into the cell. The first leads to a significant enhancement in conversion efficiency, as evident from IV characteristics and Incident Photon-to-Current Efficiency (IPCE) measurements of cells provided with SL. The latter was investigated by using angle resolved Attenuated Total Reflection (ATR) technique that evidenced a strong angular dependence of the photocurrent and further enhanced upon using a coupling prism. Both strategies are found to be based on the increase of the light path inside the active layer. [Copyright &y& Elsevier]

Imaging through scattering layers has a wide range of applications. However, even a thin layer can scatter the light into a random speckle pattern thus difficult to image. Speckle correlation-based methods enable noninvasive imaging of objects hidden behind such layers whereas, still suffer from inaccurate solutions and losing the orientation information of the object. In this paper, we proposed a novel deterministic phase-retrieval algorithm to fully reconstruct the object from its speckle pattern and experimentally demonstrated that the new method can retrieve a high-quality image from a single-shot speckle pattern. Compared to other phase retrieval techniques, it maintains the orientation information correctly in a single reconstruction and is more robust in noisy conditions. [ABSTRACT FROM AUTHOR]

Abstract: Thin titaniumdioxide (TiO2) semiconductor layer with different scattering layers was investigated in dye-sensitized solar cells (DSSC). Since the cost of the photoactive dye in the DSSC is relatively high, it is reasonable to assume that the price of the dye could be one of the decisive factors in determining the price of the DSSC modules. Use of a thin layer of nanocrystalline TiO2 would imply reduction in the amount of dye coverage, however, lower amount of dye in the thin films would imply fewer electron generation upon illumination. Thus, it becomes necessary to include a light scattering layer such that the lower photon conversion due to thin layer could be compensated. In the present study up to 80% increase in current density was observed due to inclusion of scattering layers. Reflectance and transmittance measurements were employed in order to study the optical properties of these scattering layers. The scattering layers, which are considered here, are TiO2-Rutile, zirconiumdioxide (ZrO2), and layers consisting of these two in various proportions. With a 4μm thin titanium dioxide semiconductor layer as photo electrode and an additional light scattering layer (consisting of TiO2-Rutile and ZrO2 in a ratio of 1:3), efficiencies of 6.8% were achieved. [Copyright &y& Elsevier]

The Hawaiian mesopelagic boundary community, consisting of island-associated, midwater sound-scattering layers, undergoes diel migrations with both vertical and horizontal components. To understand the dynamics of the community''s migration at fine temporal scales, we utilized a bottom-mounted, 200-kHz active-acoustic mooring that transmitted 10 signals every 15 min, from dusk until dawn for 5 days. Five moorings were deployed 1.0–3.0 km from the leeward coast of Oahu in 0.5 km intervals. Two layers within the boundary community were observed to undergo simultaneous diel vertical and horizontal migration. The shallow layer came within 10 m of the surface and 1 km of the shoreline. The deeper layer remained 90 m from the surface and 2.5 km of the shoreline. Vertical migration rates were measured at 0–1.7 m min–1 while the horizontal rate averaged 1.7 km h–1, swamping the vertical movement. The turning point of the migration pattern was observed 45 min before the midpoint between sunset and sunrise. Until the migration''s turning point, scattering strength increased relatively constantly as the animals migrated towards shore, with the highest scattering densities found in the shallowest areas at midnight. Total scattering strength measured at the leading and trailing edge of the layer support the hypothesis that increased animal densities nearshore are related to packing as mesopelagic animals avoid the surface and the bottom. We observed high levels of biomass moving rapidly, over a great distance, into shallow waters very close to shore providing insight into the significant link the mesopelagic boundary community provides between nearshore and oceanic systems. [Copyright &y& Elsevier]

Mesopelagic communities are characterized by a large biomass of diverse macrozooplankton and micronekton (MM) performing diel vertical migration (DVM) connecting the surface to the deeper ocean and contributing to biogeochemical fluxes. In the Southern Ocean, a prominent High Nutrient Low Chlorophyll (HNLC) and low carbon export region, the contribution of MM to the vertical carbon flux of the biological pump remains largely unknown. Furthermore, few studies have investigated MM communities and vertical flux in naturally iron fertilized areas associated with shallow bathymetry. In this study, we assessed the MM community diversity, abundance and biomass in the Kerguelen Island region, including two stations in the HNLC region upstream of the islands, and two stations in naturally iron fertilized areas, one on the Plateau, and one downstream of the Plateau. The MM community was examined using a combination of trawl sampling and acoustic measurements at 18 and 38 kHz from the surface to 800 m. A conspicuous three-layer vertical system was observed in all areas - a shallow scattering layer, SSL, between 10 and 200 m; mid-depth scattering layer, MSL, between 200 and 500 m; deep scattering layer, DSL, between 500 and 800 m - but communities differing among stations. While salps (Salpa thompsoni) dominated the biomass at the productive Kerguelen Plateau and the downstream station, they were scarce in the HNLC upstream area. In addition, crustaceans (mainly Euphausia vallentini and Themisto gaudichaudii) were particularly abundant over the Plateau, representing a large, although varying, carbon stock in the 0–500 m water layer. Mesopelagic fish were prominent below 400 m where they formed permanent or migrant layers accounting for the main source of carbon biomass. Through these spatial and temporal sources of variability, complex patterns of the MM vertical distribution and associated carbon content were identified. The total carbon flux mediated by migratory myctophids at the four stations was quantified. While this flux was likely underestimated, this study identified the main components and mechanisms of active carbon export in the region and how they are modulated by complex topography and land mass effects. • Macrozooplankton and micronekton communities are described in the Kerguelen area using trawl and acoustic • Despite different assemblages, a consistent three-layers system occurred in the first 800 m over the Kerguelen seascape • Salps dominated global biomass in productive areas but not in HNLC region while crustaceans were abundant on the Plateau • Myctophids dominated below 400 m as permanent or migrant layers accounting for the main source of carbon biomass • We estimate total carbon flux mediated by migratory myctophids in the contrasting productive areas [ABSTRACT FROM AUTHOR]

Mesopelagic sound scattering layers (SSLs) are predominantly associated with mesopelagic fish taxa with gas-inflated swimbladders that perform active nocturnal diel vertical migration (DVM), like species of the families Myctophidae, Gonostomatidae, Sternoptychidae and Phosichthyidae. Larger-sized species with limited, partial, asynchronous and non-migratory migration pattern (non-DVM) and without gas-bearing swimbladders are presumably invisible by hydroacoustic methods operating at lower frequencies (18–38 kHz). Their vertical migration behaviour and functional role in the mesopelagic community remain largely disregarded. The present study investigated (i) the taxonomic and functional mesopelagic fish composition (migration behaviour and feeding guild as traits) of the main SSLs and (ii) regional variation in the vertical community structure related to the presence of the oxygen minimum zone (OMZ) in the eastern tropical North Atlantic. We analysed hydroacoustic and biological trawl data collected concurrently with a pelagic midwater trawl in distinct SSLs between 45 and 680 m depth by means of ordination, cluster and compositional analyses. Whereas daytime hydroacoustic backscatter profiles demonstrated higher mean S v (38 kHz) backscatter at shallower depths at low-oxygen (LO) station 309 compared to the equatorial (EQ) station 330, night-time hydroacoustic profiles at LO stations could not be directly related to OMZ conditions. Catch abundances and biomass showed no clear regional pattern between EQ and LO stations. The analysis of trawl samples emphasised the importance of non-DVM species to the composition of tropical SSLs and further indicated regional and vertical variation in the mesopelagic fish community structure. At all stations, non-DVM species made up the largest proportions of total tow community composition (abundance and biomass) in the principal and secondary mesopelagic SSL during night-time (375–680 m) and during most daytime tows (LO: 390–555 m, EQ: 325–500 m). Our analysis suggests a more pronounced gradient structure in the vertical community composition of the LO compared to the EQ. On the one hand, shallower tows at eastern LO stations 306 and 311 were clustered with comparatively deeper tows. The eastern LO stations 306–315 had the highest numbers of non-DVM species in the principal epi- and mesopelagic SSL and the largest proportions of mesopelagic predatory species in the principal mesopelagic SSL. On the other hand, only the dominant DVM-species of the LO (i.e., Nannobrachium isaacsi , Ceratoscopelus warmingii , Notoscopelus resplendens, Lepidophanes guentheri and Hygophum macrochir) also showed consistent presence in the principal mesopelagic SSL during night-time. Moreover, our study demonstrates the usefulness of using biomass as additional parameter, when investigating functional aspects of mesopelagic community structure. • Night-time hydroacoustic backscatter profiles were not related to OMZ. • Non-DVM fishes dominated night- and most daytime catches in mesopelagic SSLs. • Eastern OMZ had highest non-DVM species numbers in epi- and mesopelagic SSLs. • Separation between epi- and mesopelagic communities was less pronounced in the OMZ. • Biomass was useful as additional parameter in the analysis of functional structure. [ABSTRACT FROM AUTHOR]

Solar photovoltaic cells are suitable alternatives to provide renewable, low-cost, and green energies. Dye-sensitized solar cells (DSSCs) have gained wide consideration owing to many properties such as transparency, low production costs, and the ability to operate in indoor lighting compared with the first generation of solar cells. Many investigations have been performed to improve the photovoltaic parameters in DSSCs by focusing on the photoanode layer. Among photoanodes, bifunctional ones, which can provide a set of essential and appropriate features in a structure, are so practical. Bifunctional photoanodes introduced as bi-layer or tri-layer photoanodes include some nanostructures as underlayer and some nanostructures with a remarkable surface area as over layer or light-scattering layer. This review can be a guide to the design and synthesis of bifunctional photoanodes with different structures. These photoanodes are useful not only for light-harvesting and light-scattering, but also for dye loading and the improvement of the J SC value and, thus, the increase of efficiency in DSSCs. This article presents recent achievements and strategies to design different bifunctional photoanodes, especially two types of photoanodes based on TiO 2 and ZnO bifunctional materials. • Different bifunctional or multifunctional photoanode materials and structures are introduced. • Multifunctional photoanodes can provide a set of essential features simultaneously. • Multifunctional photoanodes are useful for light harvesting, dye loading, enhancing J sc and efficiency in DSSCs. [ABSTRACT FROM AUTHOR]