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Incorporating specific motifs to provide tangible evidence of authenticity is a direct and effective measure against counterfeiting. However, achieving multi‐level anticounterfeiting through multiple motifs requires utilizing numerous stimulus sources to configure region‐specific emissions with customizable colors, which is complex, costly, and inaccessible. To address this challenge, a hybrid luminescent display is developed by integrating an internal down‐conversion layer with an organic light‐emitting diode (OLED). The internal down‐conversion layer can effectively extract the substrate and waveguide modes, resulting in a very rare outcome where the efficiency of a hybrid down‐conversion white OLED exceeds that of the pump light source. More importantly, by combining voltage‐modulated color‐tunable electroluminescence (EL) with EL‐induced down‐conversion luminescence, this unique design can precisely create dynamic and configurable multi‐color display patterns using only electrical stimulation. For anticounterfeiting purposes, the further amalgamation of the dynamic hybrid luminescent display device with the Internet of Things for digital authentication, and with fingerprint features for physical unclonable functions showcases unprecedented security. These results herald a new generation of multilevel luminescent anticounterfeiting technology. [ABSTRACT FROM AUTHOR]

Light is a promising renewable energy source and can be converted into heat, electricity, and chemical energy. However, the efficiency of light‐energy conversion is largely hindered by limited light‐absorption coefficients and the low quantum yield of current‐generation materials. Photonic crystals (PCs) can adjust the propagation and distribution of photons because of their unique periodic structures, which offers a compelling platform for photon management. The periodicity of materials with an alternating refractive index can be used to manipulate the dispersion of photons to generate the photonic bandgap (PBG), in which light is reflected. The slow photon effect, i. e., photon propagation at a reduced group velocity near the edges of the PBG, is widely regarded as another valuable optical property for manipulating light. Furthermore, multiple light scattering can increase the optical path, which is a vital optical property for PCs. Recently, the light reflected by PBG, the slow photon effect, and multiple light scattering have been exploited to improve light utilization efficiency in photoelectrochemistry, materials chemistry, and biomedicine to enhance light‐energy conversion efficiency. In this review, the fabrication of opal or inverse opal PCs and the theory for improving the light utilization efficiency of photocatalysis, solar cells, and photoluminescence regulation are discussed. We envision photon management of opal or inverse opal PCs may provide a promising avenue for light‐assisted applications to improve light‐energy‐conversion efficiency. [ABSTRACT FROM AUTHOR]

Tunable bandgaps make halide perovskites promising candidates for developing tandem solar cells (TSCs), a strategy to break the radiative limit of 33.7% for single‐junction solar cells. Combining perovskites with market‐dominant crystalline silicon (c‐Si) is particularly attractive; simple estimates based on the bandgap matching indicate that the efficiency limit in such tandem device is as high as 46%. However, state‐of‐the‐art perovskite/c‐Si TSCs only achieve an efficiency of ~32.5%, implying significant challenges and also rich opportunities. In this review, we start with the operating mechanism and efficiency limit of TSCs, followed by systematical discussions on wide‐bandgap perovskite front cells, interface selective contacts, and electrical interconnection layer, as well as photon management for highly efficient perovskite/c‐Si TSCs. We highlight the challenges in this field and provide our understanding of future research directions toward highly efficient and stable large‐scale wide‐bandgap perovskite front cells for the commercialization of perovskite/c‐Si TSCs. [ABSTRACT FROM AUTHOR]

Conversion of solar energy into chemical energy through natural photosynthesis plays a crucial role in sustainable energy transformation, bioresource production, and CO2 biofixation. Nevertheless, the overall solar energy to chemical energy (biomass) conversion efficiency in the photosynthetic organisms is still unsatisfactory because of their inefficient utilization of solar light. Here, a photonic method to improve photosynthesis of a unicellular green microalga, Chlamydomonas reinhardtii, a photosynthetic organism model is reported. For this purpose, an easy‐to‐fabricate microphotonic film is developed to improve the spectral quality of solar light reaching the microalgae through photon management (i.e., simultaneous solar spectral conversion and directional fluorescent emission). This study demonstrates that the short‐term oxygen evolution rate and the long‐duration biomass production of microalgae in 200‐mL laboratory photobioreactors are enhanced by a factor of 38% and 54%, respectively. In 5000‐mL scaled‐up bubble column photobioreactors placed outdoor under natural sunlight and weather conditions, the biomass yield is improved by more than 20% when compared to the control experiments conducted in parallel in an optically clear bubble column photobioreactor. Based on such experimental observations, the work here demonstrates the potential of photon management for promoting the solar energy‐to‐biomass conversion process of microalgae and other photosynthetic organisms. [ABSTRACT FROM AUTHOR]

Ion beam modification is a one-of-a-kind approach for engineering nanomaterials to change their chemical and physical properties. Ion beam engineering of metal oxide semiconductor nanoparticles has been performed to improve their optoelectronic properties considering their energy applications. Zinc Oxide (ZnO) is one of these developing wide band gap semiconductor materials with remarkable optoelectronic features that has piqued the scientific community's curiosity for a number of energy applications. Through the implantation of distinct ions at varied parameters, the low energy ion beam approach has been widely used to modify the structural, morphological, and optoelectronic features of ZnO thin film-based devices (i.e. dose, energy etc.). It offers a promising approach for controlling implantation-induced defects and associated emission in ZnO thin films. On the one hand, inert ion bombardment causes consistent surface patterning to form on ZnO, while on the other, it creates nucleation centers for the creation of nanostructures. Due to the significant radiation resistance of ZnO thin films, tuning of different properties can be studied with little to no irreparable damage to the crystal lattice. In this context, rare earth metal ion implantation in ZnO thin films represents an alternate option for study in the realm of luminescent-based applications, such as solar cells and lighting. This paper focuses on the utility of such ion implantation procedures in optoelectronic devices such as solid-state lighting and solar cells, using ZnO as a prototype material. A correlation amongst the ion implantation induced defects, conductivity and optical behaviour has also been highlighted for in-depth understanding of implantation related effects in ZnO thin film based optoelectronic devices for solar cells and lighting applications.

Photon down-converting filters with fluorescent proteins (FPs) are a new frontier in the quest for rare-earth-free and non-toxic color filters for white light-emitting diodes. There are, however, concerns related to the FP purification costs and lack of FP recyclability/reuse. Here, the direct use of bacteria in photon down-converting filters can be of utmost relevance, eliminating purification and allowing in situ production of new FPs. However, their high background autofluorescence/scattering and low stability in polymer coatings have traditionally hampered the application of Engineering Living Materials (ELMs) for photon manipulation. Indeed, there are no examples of ELMs in lighting systems. This work discloses the first protocol to prepare living spheroplasts with > 90% scattering reduction, high FP expression fairly keeping their photoluminescence figures-of-merit, and excellent resilience in polymer films over 1 year under ambient storage. This unlocked the preparation of the first bacteria hybrid light-emitting diodes integrating ELMs for photon conversion. These devices feature similar stabilities to those using purified FPs, while enabling a cost-effective strategy and active FP recycling by the simple recultivation of spheroplasts. Overall, this work introduces a successful case toward bacteria-polymer photon manipulation, in general, and a new living lighting concept, in particular., (© 2024 The Author(s). Advanced Materials published by Wiley‐VCH GmbH.)

This work reports the fabrication and characterization of multifunctional, nanostructured passivation layers formed using a self-assembly process that provide both surface passivation and improved light trapping in crystalline silicon photovoltaic (PV) cells. Scalable block copolymer self-assembly and vapor phase infiltration processes are used to form arrays of aluminum oxide nanostructures (Al2O3) on crystalline silicon without substrate etching. The Al2O3 nanostructures are characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and spectroscopic ellipsometry. Injection-level dependent photoconductance measurements are used to determine the effective carrier lifetime of the samples to confirm the nanostructures successfully passivate the Si surface. Finite element method simulations and reflectance measurement show that the nanostructures increase the internal rear reflectance of the PV cell by suppressing the parasitic optical losses in the metal contact. An optimized morphology of the structures is identified for their potential use in PV cells as multifunctional materials providing surface passivation, photon management, and carrier transport pathways.

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has increased rapidly to 25.7% in 2022. There is growing curiosity about whether it will increase further up to the PCE limit. Understanding the fundamental energy loss mechanism and targeted treatment is the crux to step forward, especially the definite and management of photons in PSCs. Here, we first briefly review the main modes of photon energy loss in PSCs and illustrate the significance of photon recycling. Next, historical research trials to overcome these loss mechanisms in PSCs are highlighted, including the application of anti-reflection coatings, plasmonic strategies, and the adoption of upconversion and downconversion materials. Finally, we make a brief summary and prospect about strategies that can help to improve photon management in the future.

In recent years, halide perovskite solar cells (HPSCs) have attracted a great attention due to their superior photoelectric performance and the low‐cost of processing their quality films. In order to commercialize HPSCs, the researchers are focusing on developing high‐performance HPSCs. Many strategies have been reported to increase the power conversion efficiency and the long‐term stability of HPSCs over the past decade. Herein, we review the latest efforts and the chemical‐physical principles for preparing high‐efficiency and long‐term stability HPSCs in particular, concentrating on the perovskite materials, technologies for perovskite films, charge transport materials and ferroelectric effect to reduce the carrier loss, and photon management via plasmonic and upconversion effects. Finally, the key issues for future researches of HPSCs are also discussed with regard to the requirements in practical application. [ABSTRACT FROM AUTHOR]

Abstract In recent years, halide perovskite solar cells (HPSCs) have attracted a great attention due to their superior photoelectric performance and the low‐cost of processing their quality films. In order to commercialize HPSCs, the researchers are focusing on developing high‐performance HPSCs. Many strategies have been reported to increase the power conversion efficiency and the long‐term stability of HPSCs over the past decade. Herein, we review the latest efforts and the chemical‐physical principles for preparing high‐efficiency and long‐term stability HPSCs in particular, concentrating on the perovskite materials, technologies for perovskite films, charge transport materials and ferroelectric effect to reduce the carrier loss, and photon management via plasmonic and upconversion effects. Finally, the key issues for future researches of HPSCs are also discussed with regard to the requirements in practical application.

Broadband absorption is pivotal for the realization of green energy based on solar energy. Decoration of photovoltaic cells with arrays of subwavelength formations provides an efficient means for broadband absorption in thin films. Surface arrays of silicon light funnels (LFs) have been suggested as a promising platform to produce broadband absorption that is considerably superior to other subwavelength arrays such as the well‐known nanopillar (NP) arrays. The current study explores the underlying mechanism of broadband absorption in LF arrays. To this end, the optical near‐field of LF and NP arrays is experimentally probed using a near‐field scanning optical microscopy. It is shown that in LF arrays the near‐field increases as the array period decreases in contrast with NP arrays in which the near‐field decreases with decreasing array period. Also, the experimental near‐field of the arrays follows the numerically calculated absorption cross section of the array‐nested NPs/LFs. Therefore, the origin to the broadband absorption in compact LF arrays is due to field overlap of adjacent LFs which increases the absorption cross section of the individual LFs composing the array. This absorption cross‐sectional enhancement coupled with a higher filling ratio in compact arrays produces broadband absorption that is significantly greater than that of NP arrays. [ABSTRACT FROM AUTHOR]

Broadband and omnidirectional antireflective surfaces are important to various solar energy technologies. The utilization of deep subwavelength features is reported for decrement in the broadband and omnidirectional reflection of the solar spectrum. The study commences with nanopillar (NP) arrays that are well known for their antireflection properties. Deep subwavelength features to the nanopillar arrays are introduced, which yield further decrease in reflection: quasinanolens (qNL), deep subwavelength sidewall scalloping (DSSS), and decreasing the nanopillar bottom diameter to reshape it into a light funnel (LF). Accordingly, surface silicon arrays are realized in a top−down fabrication process: nanopillar arrays, nanopillar arrays incorporated with DSSS, nanopillar arrays incorporated with qNL, nanopillar arrays incorporated with qNL and DSSS, and nanopillar arrays that are transformed into LF arrays and are complemented with qNL and DSSS. It is experimentally shown that utilization of deep subwavelength features produces a broadband reflection decrement with an almost 80% decrement for normal incidence and 60% decrement for an angle of incidence of 80°, for unpolarized illumination. The introduction of deep subwavelength features concludes a 20% decrement in the broadband diffused reflection compared with undecorated NP arrays. The effect of deep subwavelength features is also explored numerically, and the possible underlying light‐trapping mechanisms are discussed. [ABSTRACT FROM AUTHOR]

Abstract Energy conversion efficiency losses and limits of perovskite/silicon tandem solar cells are investigated by detailed balance calculations and photon management. An extended Shockley–Queisser model is used to identify fundamental loss mechanisms and link the losses to the optics of solar cells. Photon management is used to minimize losses and maximize the energy conversion efficiency. The influence of photon management on the solar cell parameters of a perovskite single-junction solar cell and a perovskite/silicon solar cell is discussed in greater details. An optimized solar cell design of a perovskite/silicon tandem solar cell is presented, which allows for the realization of solar cells with energy conversion efficiencies exceeding 32%.

The optical conductivity of single layer graphene (SLG) can be significantly and reversibly modified when the Fermi level is tuned by electrical gating. However, so far this interesting property has rarely been applied to free-space two-dimensional (2D) photonic devices because the surface-incident absolute absorption of SLG is limited to 1%–2%. No significant change in either reflectance or transmittance would be observed even if SLG is made transparent upon gating. To achieve significantly enhanced surface-incident optical absorption in SLG in a device structure that also allows gating, here we embed SLG in an optical slot-antenna-coupled cavity (SAC) framework, simultaneously enhancing SLG absorption by up to 20 times and potentially enabling electrical gating of SLG as a step towards tunable 2D photonic surfaces. This framework synergistically integrates near-field enhancement induced by ultrahigh refractive index semimetal slot-antenna with broadband resonances in visible and infrared regimes, ~ 3 times more effective than a vertical cavity structure alone. An example of this framework consists of self-assembled, close-packed Sn nanodots separated by ~ 10 nm nanogaps on a SLG/SiO2/Al stack, which dramatically increases SLG optical absorption to 10%-25% at λ = 600–1,900 nm. The enhanced SLG absorption spectrum can also be controlled by the insulator thickness. For example, SLG embedded in this framework with a 150 nm-thick SiO2 insulating layer displays a distinctive red color in contrast to its surrounding regions without SLG on the same sample under white light illumination. This opens a potential path towards gate-tunable spectral reflectors. Overall, this work initiates a new approach towards tunable 2D photonic surfaces. [ABSTRACT FROM AUTHOR]

Nanostructured surface, a promising photon management strategy, enables to enhance photon-to-heat conversion efficiency by manipulating spectral radiative properties ranging from solar spectrum (0.3–2.5 μm) to mid-infrared spectrum (2.5–20 μm). Here, a core–shell nanocone structured surface made of silica core and tungsten shell as a solar selective absorber is introduced. The photothermal conversion efficiency (PTCE) is calculated in consideration of solar spectrum absorption and mid-infrared emission. It is obvious that high solar spectrum absorption and low mid-infrared emission are beneficial for high PTCE. The influence of structural parameters on the PTCE is studied, and then the absorption enhancement mechanism is elucidated in detail. Meanwhile, the influences of incident angle, polarized state, and lattice arrangement are also presented. The calculated results exhibit that our optimized solar absorber possesses the total solar absorption of 97.3% and total thermal emission of 7.6%, resulting in a maximum PTCE of 91.4% under one sun illumination conditions at normal incidence. Moreover, our solar selective absorber is independent to the incident angle and polarization state. The excellent photothermal conversion performance with wide-angle and polarization-insensitive properties for the solar selective absorber can serve as a good candidate for various solar thermal applications including seawater desalination, steam generation, thermophotovoltaic, and photocatalysis. [ABSTRACT FROM AUTHOR]

In this contribution, seminal works in the area of photon‐ and charge‐management are highlighted with focus on covalent electron donor‐acceptor conjugates built around porphyrins (Ps), on one hand, and 0D, 1D, and 2D nanocarbons, on the other hand. Photons in these conjugates are managed by Ps, while 0D, 1D, and 2D nanocarbons serve as the active component, which enable managing charges. With a few leading examples, it can be explored much beyond the simple photon‐ and charge‐management characterization and emphasize photovoltaics and photocatalysis to convert and store energy. This contribution concludes by highlighting recent progress in mixing and matching the unique charge‐management features of nanocarbons in the design of multidimensional nanocarbons. [ABSTRACT FROM AUTHOR]

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Efficient omnidirectional broadband absorption is important to various applications involving the harvest of the solar spectrum. The optical absorption dependency on oblique illumination in arrays of submicrometer‐scaled compound parabolic concentrators (CPCs) is examined. For a non‐optimized CPC array, the broadband absorption is ≈30% higher than that of a nanopillar (NP) array that is corrected for the absorption of the solar light for an angle‐of‐illumination range of 0°–80°. It is shown that enhanced absorptivity of CPC arrays, relative to the optically corrected NP array, is due to the repressed transmission for both transverse electric and transverse magnetic illumination. It is determined that the superior omnidirectional broadband absorption of a CPC array is due to strong "light bending"; in the CPC array, the optical intensity is predominantly distributed laterally, whereas in the NP array, the optical intensity is mainly directed in the vertical direction. It is shown that for the CPC array, the intensity lateral components are up to 80% higher than the lateral components in the NP array. Finally, the CPC array omnidirectional broadband absorption is governed by substantial light bending, which induces competent excitation of various asymmetric photonic states. [ABSTRACT FROM AUTHOR]

Surface arrangements of subwavelength formations are extensively discussed in the context of photocurrent enhancement for photovoltaic (PV) applications. Recently, the potential contribution of such arrangements toward photovoltage augmentation is suggested. This study numerically demonstrates the potential for photovoltage management based on arrays composed of inverted silicon cones, referred to as light funnel (LF) arrays. The transition from an optimized nanopillar (NP) array into an LF array is examined. It is shown that a decrease in NP bottom diameter (Db) is accompanied by an increase in open‐circuit voltage (Voc). The highest photovoltage enhancement is recorded for the smallest considered Db = 50 nm with a Voc increase of 75 mV and reflects a 22% Voc enhancement compared with the NP Voc. It is shown that this Voc increase is due to 250% increase in the excitation level, and that the spatially resolved excitation level of the array‐nested LFs is more than two orders of magnitude higher than the highest spatially resolved excitation level in the array‐nested NPs. Finally, it is shown that the suggested photovoltage management entails almost a factor of 2 increase in the nominal power conversion efficiency upon the transition from an NP PV cell into LF PV cell. [ABSTRACT FROM AUTHOR]

• The importance of deep NIR sensitizers for maximal SSM-DSC performance is shown. • A SSM-DSC with a power conversion efficiency of >11% is realized for the first time. • Sensitizer and redox shuttle selection has enabled >2.3 V from a SSM-DSC at >11% PCE. • Minimal potential losses allow for applications in catalysis/solar fuel generation. • A versatile architecture compatible with various solar cell technologies is shown. A sequential series multijunction dye-sensitized solar cell (SSM-DSC) designed to minimize optical and free energy losses to enable higher device performance is reported. Efficient photon management of solar spectrum irradiation was made possible by: controlling TiO 2 film thickness in each subcell leading to balanced photocurrent, careful sensitizer selection based on absorption breadth and intensity for each subcell, and minimizing photon losses by application of an anti-reflective coating with an immersion oil between subcells. By using these strategies with a deep NIR absorbing sensitizer, an SSM-DSC device based on D35/B11/Black Dye demonstrated an overall power conversion efficiency of >11% with a photovoltage of 2.3 V from a single illuminated area device. The PCE of the SSM-DSC is significantly higher than any of the individual subcell in the mechanical stack. This approach has led to a higher performing device than the prior reported high efficiency SSM-DSC devices based on D35/B11/B11 or the all organic dye SSM-DSC based on D35/MK2/AP25 + D35. [ABSTRACT FROM AUTHOR]

• Positive and negative effects of surface morphology on features of PV are studied. • Efficiency of 23.46% and bifacial utilization of 93.4% are achieved, respectively. • The temperature-dependent efficiency due to surface morphology is analyzed. • Proper structures are decided by a tradeoff between optical and electric properties. • Elaborate design of microstructures is vital for photovoltaic devices. Light-trapping structures play an important role in the application of solar cells due to their ability to enhance absorption. A dilemma related to comprehensive consideration of augmenting the light-trapping ability of surfaces of solar cells and suppressing recombination tendency induced by improper design of structured surfaces to keep in mind the ultimate goal of achieving as high solar-electric conversion efficiency of commercial photovoltaic cells as possible. This work is aimed at investigating the coupling optical-electrical properties of bifacial heterojunction with intrinsic thin-layer (HIT) solar cells on which multiscale pyramid microstructures are fabricated. Based on the results of coupling investigation, a tradeoff between optical and electrical properties are achieved with pyramids of 3–5 μm. The highest power conversion efficiency (PCE) locates at solar cells with pyramids of 3–5 μm. The best PCE amounts respectively to 23.46% and 21.85% with the frontal and rear illumination and the bifacial utilization can be enhanced is up to 93.4%. The output properties are superior to those of PV cells in the baseline. The interconnection between the temperature coefficient of PV conversion efficiency and dimensions of the microstructured surfaces is studied. The influences of different light-trapping structures on the ability of photon absorption and the recombination of carriers of solar cells are characterized. This work provides the guideline for selecting more appropriate structures with both benign optical and electrical properties to enhance the performance of solar cells. [ABSTRACT FROM AUTHOR]

With the practical efficiency of the silicon photovoltaic (PV) cell approaching its theoretical limit, pushing conversion efficiencies even higher now relies on reducing every type of power loss that can occur within the device. Limiting optical losses is therefore critical and requires effective management of incident photons in terms of how they interact with the device. Ultimately, photon management within a PV cell means engineering the device and constituent materials to maximize photon absorption within the active semiconductor and therefore reduce the number of photons lost through other means, most notably reflection and parasitic absorption. There have been great advancements in the front and the rear side photon management techniques in recent years. This review aims to discuss these advancements and compare the various approaches, not only in terms of increases in photogenerated current, but also their compatibility with different PV cell architectures and potential trade-offs, like increased surface recombination or scalability for high-volume manufacturing. In this review, a comprehensive discussion of a wide variety of the front and the rear side photon management structures are presented with suggestions to improve the already achieved performance further. This review is unique because it not only presents the recent development in photon management techniques, but also offers through analysis of these techniques and pathways to improve further. • A thorough exploration of diverse front and rear photon management structures is presented. • Suggestions for further improving the already achieved cell performance are offered. • Explains underlying physics and material properties dictating various energy conversion losses in PV cells. • Explores optical benefits of photon management structures and their impact on recombination and resistive losses. • This unique review discusses recent advances in photon management and provides in-depth analysis with pathways for further improvement. [ABSTRACT FROM AUTHOR]

Abstract In the field of photovoltaics, achieving high efficiency in both light absorption and light trapping simultaneously remains challenging. Photon management, which refers to the engineering of materials and device architectures to control the spatial or spectral distribution of optical energy, offers a number of promising approaches for the optimization of this tradeoff. Among these are antireflective structures with pronounced surface patterned profiles that reduce surface reflectivity, light trapping approaches but also spectral conversion concepts. With the continuous development of photovoltaic device architectures and designs, the engineering of novel photon management strategies and the availability of suitably tailored polymeric materials for such applications will contribute to enhanced device efficiencies as well as sustained long-term performance. In this review, we summarize the recent progress in the development and implementation of photon management strategies for different photovoltaic technologies specifically based on the use of polymeric materials, and we discuss their contribution to the field. Highlights • To increase efficiency of photovoltaic devices, photon management strategies are used. • Photon management includes light-trapping and spectral conversion approaches. • Polymers are leading players in photon management approaches. • The contribution of polymeric materials to photon management systems is reviewed. [ABSTRACT FROM AUTHOR]

Abstract Improvement of solar cell performance through the parallel homo-tandem architecture is studied. The cell geometry is optically designed to maximize absorption of the AM1.5 spectrum. We consider both ITO electrode and a recently devised ITO-free alternative, the Two-Resonance Tapping Cavity. The optimal geometry strongly depends on this choice. We identify two mechanisms by which tandem cells outperform single cells: (i) back-up absorption and (ii) interferometric gain mediated by the central metallic electrode. We numerically demonstrate large improvement in short-circuit current for a wide choice of realistic materials: PTB7-th:PC 71 BM, P3HT:PC 61 BM, DBP:C 70 , and methylammonium lead halide perovskite, as well as a theoretical material with a Shockley-Queiser type of spectral absorption plus an Urbach tail. Such an idealized response is found to reliably model real materials. A general response pattern is found that fits all the cases covered in our study, and which can serve as a guide to optimize homo-tandem cells. Highlights • 3-terminal thin film homo-tandem solar cells are optically optimized. • Both with ITO and ITO-free transparent electrodes are considered. • Gain in performance comes from microcavity effects and back-up absorption. • The optimal silver central electrode thickness is large (up to 20 nm). • Optimization of the two subcells is independent. [ABSTRACT FROM AUTHOR]

The unique optical properties possessed by plasmonic noble metal nanostructures in consequence of localized surface plasmon resonance (LSPR) are useful in diverse applications like photovoltaics, sensing, non-linear optics, hydrogen generation, and photocatalytic pollutant degradation. The incorporation of plasmonic metal nanostructures into solar cells provides enhancement in light absorption and scattering cross-section (via LSPR), tunability of light absorption profile especially in the visible region of the solar spectrum, and more efficient charge carrier separation, hence maximizing the photovoltaic efficiency. This review discusses about the recent development of different plasmonic metal nanostructures, mainly based on Au or Ag, and their applications in promising third-generation solar cells such as dye-sensitized solar cells, quantum dot-based solar cells, and perovskite solar cells.

Abstract Photon management is an efficient way to increase the performance of photovoltaic (PV) devices with light trapping. However, the efficiency of PV is limited by the bandgap of materials. To take advantages of photons over the whole AM1.5G spectrum, thermoelectric (TE) devices are added to the bottom of PV as hybrid systems to utilize the rest solar energy through thermal utilization. In this way, photon management inside PV cells is extended to two aspects: the absorption of spectrally high-graded photons and the transmission of photons below the bandgap to TE devices. From this point of view, structures on both top side and bottom side in solar cells must be designed for the required management. In this way, double-side structures are presented on the surface of thin-film silicon, which consist of nanocones and bioinspired honeycomb-arranged holes. With optimized parameters, excellent anti-reflection property and near-infrared (NIR) transmission are achieved over the full-spectrum and NIR wavelength range, respectively. The integrated honeycomb holes will further enhance absorption with wavelengths of 300–1100 nm through combined gradient effective refractive index and scattering effects with effective transmittance with wavelengths of 1100–2500 nm, simultaneously. The results also scarcely depend on the variation of incident angles and polarization states. This optical selective control in solar cells is called urgently for full-spectrum solar applications with solar cells. Highlights • Double-side surface is designed for full-spectrum photon management. • A cone/honeycomb integrated structure is proposed. • Bottom-side structures enables remarkable transmission of near-infrared photons • Omnidirectional and Polarization-insensitive optical properties are obtained. [ABSTRACT FROM AUTHOR]

Summary: Photon management and carrier separation play crucial roles on designing highly efficient organic‐silicon heterojunction solar cells. Aiming at suppressing optical reflection loss and improving carrier separation efficiency simultaneously, in this paper, we experimentally fabricated hybrid nanostructured/microstructured surfaces by combining the advantages of microstructures and nanostructures. The hybrid nanostructured/microstructured surfaces were prepared by stacking nanoholes on the micropyramids via using a cost‐effective method. In terms of the optical properties, the light reflection, angle‐dependent light absorption, and polarization‐dependent light absorption of the different structured surfaces were investigated. The results indicated that the hybrid nanostructures/microstructures exhibited ultralow reflection in the broadband wavelength range of 300 to 1100 nm (average reflection is 1.8%). Meanwhile, the hybrid nanostructured/microstructured surfaces possessed superior omnidirectional and polarization‐independent properties compared to the unitary structures such as pyramid and nanohole. Furthermore, these different structured surfaces were simply used to fabricate the PEDOT:PSS/n‐Si heterojunction solar cells to show the electrical properties. It was found that the PEDOT:PSS/hybrid Si solar cells showed a PCE of 9.96%, which was greater than the PEDOT:PSS/pyramid Si and PEDOT:PSS/black Si solar cells, owing to the compromise among light absorption, junction area, and minority carrier lifetime. The present work will provide a promising way to fabricate high‐performance and low‐cost PEDOT:PSS/n‐Si heterojunction solar cells by using hybrid nanostructured/microstructured surfaces. [ABSTRACT FROM AUTHOR]

Nanotextured diamond-wire sawing (DWS) multi-crystalline silicon (mc-Si) solar cells are successfully fabricated on an industrial scale. The nanotextures are achieved through reactive ion etching (RIE). By introducing the RIE-nanotextures, the DWS mc-Si solar cells with aluminum back-surface field (Al-BSF) structure exhibit an enhanced optoelectronic conversion, and high power conversion efficiency ( PCE ) of up to 19.50%. This enhanced optoelectronic conversion is attributed to nanotexture-induced photon management effect, including both efficient reflection reduction and absorption enhancement, and which offset over the increased recombination of charge carriers. The DWS mc-Si solar cells are promising for industrial production due to the low raw material cost, high PCE, and manufacturing processes compatible with the existing production lines. [ABSTRACT FROM AUTHOR]

Highlights • The negative effect of UV light on the perovskite solar cells is greatly suppressed. • Light harvesting performance for Vis-NIR band is simultaneously enhanced. • The power conversion efficiency of the perovskite solar cells is improved. Abstract In spite of the explosive enhancement to the device performance of the perovskite solar cells (PSCs) over the past decade, the intrinsic instability and performance degradation under ultraviolet (UV) illumination still impedes applications of such solar-electric conversion devices. Herein, we propose novel photon management structures (PMSs) including one-dimensional photonic crystal (1DPC) and self-cleaning biomimetic moth-eye structure (BMES) for simultaneously shielding the PSCs from the harmful UV irradiation and enhancing light harvesting for the useful visible-near infrared (Vis-NIR) irradiation. Optical and electrical simulation models, which are validated by the experimental results, are carried out to investigate how the PMSs with various structure parameters influence the optical and electrical properties of the PSCs. It is proved that with optimized PMSs, the PSCs would perform remarkable high reflection for UV band and low reflection for Vis-NIR band. This can perfectly suppress the negative effects of UV light on PSCs as well as further improve the power conversion efficiency (PCE) of the photovoltaic devices. [ABSTRACT FROM AUTHOR]

Although texturing of the transparent electrode of thin-film solar cells has long been used to enhance light absorption via light trapping, such texturing has involved low aspect ratio features. With the recent development of nanotechnology, nanostructured substrates enable improved light trapping and enhanced optical absorption via resonances, a process known as photon management, in thin-film solar cells. Despite the progress made in the development of photon management in thin-film solar cells using nanostructures substrates, the structural integrity of the thin-film solar cells deposited onto such nanostructured substrates is rarely considered. Here, we report the observation of the reduction in the open circuit voltage of amorphous silicon solar cells deposited onto a nanostructured substrate with increasing areal number density of high aspect ratio structures. For a nanostructured substrate with the areal number density of such nanostructures increasing in correlation with the distance from one edge of the substrate, a correlation between the open circuit voltage reduction and the increase of the areal number density of high aspect ratio nanostructures of the front electrode of the small-size amorphous silicon solar cells deposited onto different regions of the substrate with graded nanostructure density indicates the effect of the surface morphology on the material quality, i.e., a trade-off between photon management efficacy and material quality. This observed trade-off highlights the importance of optimizing the morphology of the nanostructured substrate to ensure conformal deposition of the thin-film solar cell. [ABSTRACT FROM AUTHOR]

Silicon light funnels are three-dimensional subwavelength structures in the shape of inverted cones with respect to the incoming illumination. Light funnel (LF) arrays can serve as efficient absorbing layers on account of their light trapping capabilities, which are associated with the presence of high-density complex Mie modes. Specifically, light funnel arrays exhibit broadband absorption enhancement of the solar spectrum. In the current study, we numerically explore the optical coupling between surface light funnel arrays and the underlying substrates. We show that the absorption in the LF array-substrate complex is higher than the absorption in LF arrays of the same height (~10% increase). This, we suggest, implies that a LF array serves as an efficient surface element that imparts additional momentum components to the impinging illumination, and hence optically excites the substrate by near-field light concentration, excitation of traveling guided modes in the substrate, and mode hybridization. [ABSTRACT FROM AUTHOR]

In order to break through the limit of low power conversion efficiency (PCE) of dye-sensitized solar cell (DSSC) with single photon management architecture in photoanode, herein, we propose a novel architecture, composed of a TiO 2 nanotube photonic crystal (TiO 2 NTPC) layer and in-suit deposited Au plasmonic nanoparticles (Au NPs), as photoanode for DSSC applications. The designed photoanode is expected to significantly increase the light harvesting in DSSCs, due to the synergistic effect of the photonic crystal (PC) effect originates from TiO 2 NTPC and the surface plasmon resonance (SPR) effect from Au NPs. This synergistic effect of the newly designed photoanode and its functionality in DSSCs are discussed by both experimental and simulated results. Moreover, when the SPR band of Au NPs has been tailored to best match with the bandgap of TiO 2 NTPC, the maximum enhancement in power conversion efficiency (PCE, 44.7%), which exceeds the sum enhancement producing by coupling individual TiO 2 NTPC (22.1%) or Au NPs (18.0%), has been achieved by introducing the designed Au NPs/TiO 2 NTPC photoanode, yielding a PCE of 5.63% in the NT-based DSSCs. The work presented here provides new insights into the design and application of SPR/PC coupling architectures for high efficient light management and synergistically enhanced light harvesting in photovoltaic devices. [ABSTRACT FROM AUTHOR]

Organic photovoltaic (OPV) cells and organic light-emitting diodes (OLEDs) are energy harvesting and generation devices that have attracted great attention these years because of their low costs, thin film structures, flexibility and environment-friendly manufacturing processes. For such thin film devices, photon management methods that increase the light absorption of OPV cells and the light extraction from OLEDs are highly desirable. Here, we report the experimental efforts to fabricate geometrically tunable and spontaneously formed nano-wrinkle structures with large areas, and the theoretical results on photon management with the nano-wrinkles. [ABSTRACT FROM AUTHOR]

Plasmonic gratings provide effective photon management techniques in thin-film solar cells, capable of extending the optical thickness of the solar cell’s active layer. However, the ultra-broadband nature of such application makes an optimal design of the grating structure quite challenging, since a fully periodic grating operates only in specific spectral ranges. To achieve a more broadband design, semiperiodicity is introduced, which, due to having controllable disorder, is an apt solution in broadband optical applications. In this work, semiperiodic double gratings as a broadband photon management technique are introduced in order to improve the optical absorption of c-Si thin-film solar cells, and optimized through numerical structural optimization. Physical parameters of both front and back gratings are determined taking the spectrally integrated optical absorption as the figure of merit and subsequently a semiperiodic double grating is established through adding defects to the fully periodic structure. It is shown that such semiperiodic structure is capable of enhancing the spectrally integrated optical absorption 88.6 % compared to a reference structure without gratings.

The thermal emissivity of crystalline silicon photovoltaic (PV) solar cells plays a role in determining the operating temperature of a solar cell. To elucidate the physical origin of thermal emissivity, we have made an experimental measurement of the full radiative spectrum of the crystalline silicon (c-Si) solar cell, which includes both absorption in the ultraviolet to near-infrared range and emission in the mid-infrared. Using optical modelling, we have identified the origin of radiative emissivity in both encapsulated and unencapsulated solar cells. We find that both encapsulated and unencapsulated c-Si solar cells are good radiative emitters but achieve this through different effects. The emissivity of an unencapsulated c-Si solar cell is determined to be 75% in the MIR range, and is dominated by free-carrier emission in the highly doped emitter and back surface field layers; both effects are greatly augmented through the enhanced optical outcoupling arising from the front surface texture. An encapsulated glass-covered cell has an average emissivity around 90% on the MIR, and dips to 70% at 10 µm and is dominated by the emissivity of the cover glass. These findings serve to illustrate the opportunity for optimising the emissivity of c-Si based collectors, either in conventional c-Si PV modules where high emissivity and low-temperature operation is desirable, or in hybrid PV-thermal collectors where low emissivity enables a higher thermal output to be achieved. [ABSTRACT FROM AUTHOR]

To optimize the optical response of a solar cell, specifically designed materials with appropriate optoelectronic properties are needed. Owing to the unique microstructure of doped nanocrystalline silicon oxide, nc-SiO x :H, this material is able to cover an extensive range of optical and electrical properties. However, applying nc-SiO x :H thin-films in photovoltaic devices necessitates an individual adaptation of the material properties according to the specific functions in the device. In this study, we investigated the detailed microstructure of doped nc-SiO x :H films via atom probe tomography at the sub-nm scale, thereby, for the first time, revealing the three-dimensional distribution of the nc-Si network. Furthermore, n- and p-type nc-SiO x :H layers with various optical and electrical properties were implemented as a window, back contact, and an intermediate reflector layer in silicon heterojunction and multi-junction thin-film solar cells with a focus on the key aspects for adapting the material properties to the specific functions. Here, nc-SiO x :H effectively reduced the parasitic absorption and opened new possibilities for the photon management in the solar cells, thereby, demonstrating the versatility of this material. Remarkably, using our adapted nc-SiO x :H layers in distinct functions enabled us to achieve a combined short circuit current density of 15.1 mA cm −2 for the two a-Si:H sub-cells in an a-Si:H/a-Si:H/µc-Si:H triple-junction thin-film solar cell and an active area efficiency of 21.4% was realized for a silicon heterojunction solar cell. [ABSTRACT FROM AUTHOR]

Recent technological advances in conventional planar and microstructured solar cell architectures have significantly boosted the efficiencies of these devices near the corresponding theoretical values. Nanomaterials and nanostructures have promising potential to push the theoretical limits of solar cell efficiency even higher using the intrinsic advantages associated with these materials, including efficient photon management, rapid charge transfer, and short charge collection distances. However, at present the efficiency of nanostructured solar cells remains lower than that of conventional solar devices due to the accompanying losses associated with the employment of nanomaterials. The concurrent design of both optical and electrical components will presumably be an imperative route toward breaking the present-day limit of nanostructured solar cells. This review summarizes the losses in traditional solar cells, and then discusses recent advances in applications of nanotechnology to solar devices from both optical and electrical perspectives. Finally, a rule for nanostructured solar cells by concurrently engineering the optical and electrical design is devised. Following these guidelines should allow for exceeding the theoretical limit of solar cell efficiency soon. [ABSTRACT FROM AUTHOR]

The proposed photovoltaic (PV)–Thermoelectric (TE) hybrid system is an advanced approach to utilize full–spectrum (300–2500 nm) solar energy. In this system, incident photons in different wavelengths must be transferred to different devices via efficient allocation, which is called photon management, to enhance the performance of the hybrid systems. The photon–management property can be realized through subwavelength structures in solar cells. In this work, based on silicon solar cells, composite subwavelength structures are fabricated in crystalline silicon through ICP etching and magnetron sputtering process with the required spectral characteristics. Integrated ordered, and disordered nanopillar/nanohole arrays enable broadband absorption in the wavelength range (300–1100 nm) above the bandgap with an average absorptance of about 97%. About 60% solar energy from 1200 nm to 2500 nm can transmit to the TE devices with the assistance of the deposited TiO 2 /SiO 2 bilayer films on the bottom side. The good photon–management performance is independent of the incident angles and insensitive to the polarization states. The method can also be applied to other kinds of solar cells for the application in the PV–TE hybrid systems. This paper opens new routes to smart photon management, which is expected to have promising applications in efficient full–spectrum solar energy conversion. [ABSTRACT FROM AUTHOR]

In this work, advanced photon-management composite subwavelength structures are fabricated to manage solar energy in the full-spectrum (300–2500 nm) wavelength range for the application of the photovoltaic-thermoelectric hybrid systems to fully utilize the solar energy. This proposed photon-management method will simultaneously realize efficient light trapping for the photons with above-bandgap energy in solar cells and the utilization of the below-bandgap photons and the waste heat resulting from the thermalization effect in solar cells with bottom thermoelectric devices. The typical structure is designed: Top ordered hexagonal nanohole arrays can trap above-bandgap photons to enhance the absorption in the silicon wafer, and TiO 2 /SiO 2 bilayer films are deposited on the bottom side of the wafer to improve the transmission of the below-bandgap photons. ∼97% total absorptance for wavelengths of 300–1100 nm is achieved with optimized diameters of central nanoholes. The total transmittance, on the other hand, is improved to ∼60% from 1200 nm to 2500 nm. The results indicate that the structures realize the appropriate allocation of photons within different wavelength ranges to different devices for sufficient utilization of full-spectrum solar energy. This novel full-spectrum photon management benefits from the strong scattering effect among the nanoholes and the gradient refractive index of bilayer films. Moreover, the photon-management performance shows angle-independent and polarization-insensitive characteristics. This method can be applied to various kinds of solar cells for photovoltaic-thermoelectric hybrid systems and may provide thoughts for other solar harvesting applications. [ABSTRACT FROM AUTHOR]

Organic-inorganic perovskite solar cells have been highlighted as one of the most competitive thin film photovoltaics recently. It is promising to further raise the power conversion efficiency if high quality absorber is coupled with rational optical design for effective photon management. Here we demonstrate the implementation of perovskite nanostructure assembly by simple solution process to interfere the propagation of light inside the adjacent absorber. It enhances light harvesting to obtain higher attainable photocurrents and photovoltage in the resultant devices, achieving a decent power conversion efficiency (PCE) over 19% consequently. The presented nanostructure assembly integrates perovskite materials with desirable processibility and chemical compatibility by chemical synthesis and interface modification. For the first time, a synergetic localized “gratings” and enhanced fluorescence effect was demonstrated to govern photon management in perovskite solar cells. These findings may serve as a general guide to design and construct perovskite thin solar cells with efficiency approaching Shockley-Queisser limit. [ABSTRACT FROM AUTHOR]

The concurrent development of high-performance materials, new device and system architectures, and nanofabrication processes has driven widespread research and development in the field of nanostructures for photon management in photovoltaics. The fundamental goals of photon management are to reduce incident light reflection, improve absorption, and tailor the optical properties of a device for use in different types of energy conversion systems. Nanostructures rely on a core set of phenomena to attain these goals, including gradation of the refractive index, coupling to waveguide modes through surface structuring, and modification of the photonic band structure of a device. In this review, we present recent developments in the field of nanostructures for photon management in solar cells with applications across different materials and system architectures. We focus both on theoretical and numerical studies and on progress in fabricating solar cells containing photonic nanostructures. We show that nanoscale light management structures have yielded real efficiency gains in many types of photovoltaic devices; however, we note that important work remains to ensure that improved optical performance does not come at the expense of poor electrical properties.

Although texturing of the transparent electrode of thin-film solar cells has long been used to enhance light absorption via light trapping, such texturing has involved low aspect ratio features. With the recent development of nanotechnology, nanostructured substrates enable improved light trapping and enhanced optical absorption via resonances, a process known as photon management, in thin-film solar cells. Despite the progress made in the development of photon management in thin-film solar cells using nanostructures substrates, the structural integrity of the thin-film solar cells deposited onto such nanostructured substrates is rarely considered. Here, we report the observation of the reduction in the open circuit voltage of amorphous silicon solar cells deposited onto a nanostructured substrate with increasing areal number density of high aspect ratio structures. For a nanostructured substrate with the areal number density of such nanostructures increasing in correlation with the distance from one edge of the substrate, a correlation between the open circuit voltage reduction and the increase of the areal number density of high aspect ratio nanostructures of the front electrode of the small-size amorphous silicon solar cells deposited onto different regions of the substrate with graded nanostructure density indicates the effect of the surface morphology on the material quality, i.e., a trade-off between photon management efficacy and material quality. This observed trade-off highlights the importance of optimizing the morphology of the nanostructured substrate to ensure conformal deposition of the thin-film solar cell.

2D MoS 2 attracts increasing attention for its application in flexible electronics and photonic devices. For 2D material optoelectronic devices, the light absorption of the molecularly thin 2D absorber would be one of the key limiting factors in device efficiency, and conventional photon management techniques are not necessarily compatible with them. In this study, we show two semimetal composite nanostructures deposited on 2D MoS 2 for synergistic photon management and strain-induced band gap engineering: (1) the pseudo-periodic Sn nanodots, (2) the conductive SnO x ( x < 1) core-shell nanoneedle structures. Without sophisticated nanolithography, both nanostructures are self-assembled from physical vapor deposition. Optical absorption enhancement spans from the visible to the near-infrared regime. 2D MoS 2 achieves >8× optical absorption enhancement at λ = 700-940 nm and 3-4× at λ = 500-660 nm under Sn nanodots, and 20-30× at λ = 700-900 nm under SnO x ( x < 1) nanoneedles. The enhanced absorption in MoS 2 results from strong near-field enhancement and reduced MoS 2 band gap due to the tensile strain induced by the Sn nanostructures, as confirmed by Raman and photoluminescence spectroscopy. Especially, we demonstrate that up to 3.5% biaxial tensile strain is introduced to 2D MoS 2 using conductive nanoneedle-structured SnO x ( x < 1), which reduces the band gap by ∼0.35 eV to further enhance light absorption at longer wavelengths. To the best of our knowledge, this is the first demonstration of a synergistic triple-functional photon management, stressor, and conductive electrode layer on 2D MoS 2 . Such synergistic photon management and band gap engineering approach for extended spectral response can be further applied to other 2D materials for future 2D photonic devices.

The Si heterojunction (SHJ) solar cell is presently the most popular design in the crystalline Si ( c -Si) photovoltaics due to the high open-circuit voltages ( V OC ). Photon management by surface structuring techniques to control the light entering the devices is critical for boosting cell efficiency although it usually comes with the V OC loss caused by severe surface recombination. For the first time, the periodic inverted pyramid (IP) structure fabricated by photolithography and anisotropic etching processes was employed for SHJ solar cells, demonstrating concurrent improvement in optical and electrical characteristics (i.e., short-circuit current density ( J SC ) and V OC ). Periodic IP structures show superior light-harvesting properties as most of the incident rays bounce three times on the walls of the IPs but only twice between conventional random upright pyramids (UPs). The high minority carrier lifetime of the IP structures after a -Si:H passivation results in an enhanced V OC by 28 mV, showing improved carrier collection efficiency due to the superior passivation of the IP structure over the random UP structures. The superior antireflective (AR) ability and passivation results demonstrate that the IP structure has the potential to replace conventional UP structures to further boost the efficiency in solar cell applications. [ABSTRACT FROM AUTHOR]