Evaluation of Back Contact in Spray Deposited SnS Thin Film Solar Cells by Impedance Analysis

The role of back metal (M) contact in sprayed SnS thin film solar cells with a configuration Glass/F:SnO₂/In₂S₃/SnS/M (M = Graphite, Cu, Mo, and Ni) was analyzed and discussed in the present study. Impedance spectroscopy was employed by incorporating constant phase elements (CPE) in the equivalent circuit to investigate the degree of inhomogeneity associated with the heterojunction and M/SnS interfaces. A best fit to Nyquist plot revealed a CPE exponent close to unity for thermally evaporated Cu, making it an ideal back contact. The Bode phase plot also exhibited a higher degree of disorders associated with other M/SnS interfaces. The evaluation scheme is useful for other emerging solar cells developed from low cost processing schemes like spray deposition, spin coating, slurry casting, electrodeposition, etc

Facile, Noncyanide Based Etching of Spray Deposited Cu₂ZnSnS₄ Thin Films for Secondary Phase Removal

The coexistence of secondary phases in the quaternary compound kesterite Cu₂ZnSnS₄ (CZTS), a promising photovoltaic absorber, is a major problem while synthesizing under Zn or Cu rich conditions. A large variety of secondary phases, such as CuS, Cu_1.8S, Cu₂S, Cu₂SnS₃, and ZnS exist on the surface unless they are not removed by dedicated surface treatment before the annealing step. Under a carefully chosen concentrations of the starting precursors (usually, Zn-poor and Sn-rich) for spray pyrolyzed CZTS, the fraction of ZnS is minimized. However, under such growth conditions, binary Cu-sulfides become dominant. In this work, a selective noncyanide based chemical etching procedure is demonstrated prior to the deposition of the buffer layer. The absorber surface was treated with hydrogen peroxide that is known to remove Cu_1.8S, Cu₂S, and allied secondary phases to a large extent as compared to conventional KCN based techniques. By this treatment, the optical band gap is changed from 1.8 eV to most suitable 1.5 eV, which ensures improved photon absorption

Self-Powered Ultraviolet–Visible Transparent Photodetector Based on Mo-Doped BiVO₄ Thin Films

Till now, BiVO4 has been extensively investigated for photoelectrochemical cell applications; however, the efficacy of BiVO4 in the photodetector (PD) and photovoltaic field is still challenging due to its poor absorption ability, conductivity, and high recombination rate. Keeping these issues in mind, herein, we report a co-sputtered Mo-doped (Mo:BiVO4) thin films-based self-powered ultraviolet (UV)–visible transparent PD (TPD) with a high photo-to-dark current ratio value of 1.2 × 103 and a detectivity value of 4.1 × 1010 Jones. Mo:BiVO4-based self-powered TPD devices show a fast response speed with a value of 3.5 ms. Moreover, the fabricated TPD devices show a clear photovoltaic photoresponse with an average visible transparency value of 65%. The highest obtained open-circuit voltage value is about 300 mV with a short-circuit current density value of 2.53 mA/cm2 under visible illumination along with an onsite power production value of 44 μW. Developed Mo:BiVO4-based TPD devices explore the suitability of BiVO4 in the transparent optoelectronics and onsite power generation field for the future

Transparent Photovoltaics for Self-Powered Bioelectronics and Neuromorphic Applications

Inspired by the brain, future computation depends on creating a neuromorphic device that is energy-efficient for information processing and capable of sensing and learning. The current computation-chip platform is not capable of self-power and neuromorphic functionality; therefore, a need exists for a new platform that provides both. This Perspective illustrates potential transparent photovoltaics as a platform to achieve scalable, multimodal sensory, self-sustainable neural systems (e.g., visual cortex, nociception, and electronic skin). We present herein a strategy to harvest solar power using a transparent photovoltaic device that provides neuromorphic functionality to implement versatile, sustainable, integrative, and practical applications. The proposed solid-inorganic heterostructure platform is indispensable for achieving a variety of biosensors, sensory systems, neuromorphic computing, and machine learning

Field-Effect Passivation of the Cu₂O/ZnO Transparent Heterojunction Photovoltaic Device Using Ga₂O₃ Thin Film

Photovoltaics (PV) would be more promising if light could generate electric power invisibly. This will endow more degrees of freedom to PV cells for wide-range deployment. Transparent photovoltaic (TPV) devices are the groundwork of the building-integrated photovoltaic (BIPV) systems that provide aesthetics to the buildings and solar energy convertor modules. TPV is adequate for the BIPV system of windows. Heterojunctions between p-type Cu2O and n-type ZnO have emerged as one of the most promising TPV devices. However, their inadequate transparency and a deficit of open-circuit voltage (VOC) and short-circuit current density (JSC) remained an open challenge. In this work, we have fabricated a thin Ga2O3 buffer layer embedded transparent ZnO/Cu2O heterojunction photovoltaic device, showing an average visible transmittance of more than 50%. The insertion of the Ga2O3 buffer layer remarkably increases the JSC and VOC to ∼860% and ∼41%, respectively. The TPV device also demonstrated a high JSC of 3.41 mA/cm2 under UV light. The Ga2O3 layer provides a graded conduction band alignment and passivates the interface by the field-effect passivation mechanism. The Ga2O3 buffer layer embedded device also demonstrated a broadband photodetection with remarkably high responsivity and detectivity of 250 mA/W and 5 × 1011 Jones at self-biased conditions

MXene-Integrated Metal Oxide Transparent Photovoltaics and Self-Powered Photodetectors

MXene-integrated photovoltaic devices can be used to create optically transparent systems to produce electrical energy. MXenes, an emerging family of two-dimensional materials, have attracted a tremendous amount of interest for their use in various applications. In particular, their optical transparency, metallic conductivity, and large-scale processing make MXenes highly applicable in transparent photovoltaic devices (TPVDs). Here we propose a Ti3C2Tx MXene-based inorganic TPVD. Reducing the sheet resistance of MXene and improving its contact with the metal oxide (NiO/TiO2) heterojunction enables the generation of electric power (30 μW cm–2) from ultraviolet light while selectively passing visible light for high-transparency (39.73%). Moreover, the photovoltaic effect induces a high photovoltage of 0.45 V to enable the TPVD to work in self-powered mode. The MXene-embedded transparent photodetector works in photovoltaic mode and has a fast response speed of 80 μs and high detectivity of 1.6 × 1010 Jones. The spacing of the MXene-transparent devices at color-neutral coordinates in color maps indicates the invisibility of the device. This work demonstrates the large-scale application of MXene as a seamless platform for transparent electronics of photovoltaics and photodetectors. Transparent photoelectric interfaces can be used for energy generation; in bioelectronics; and in windows of building, vehicles, and displays

Highly Transparent Bidirectional Transparent Photovoltaics for On-Site Power Generators

If we can transparently produce energy, we may apply invisible power generators to residential architectures to supply energy without losing visibility. Transparent photovoltaic cells (TPVs) are a transparent solar technology that transmits visible light while absorbing the invisible short wavelengths, such as ultraviolet. Installing TPVs in buildings provides an on-site energy supply platform as a window-embedded power generator or color-matched solar cell installation on a building surface. The record-high power generation (10.82 mW) and photocurrent value (68.25 mA) were achieved from large-scale TPVs (25 cm2). The metal oxide heterojunction is the fundamental TPV structure. The high-performance TPVs were achieved by adopting a thin Si film between ZnO and NiO as a functional light-absorbing layer. Based on the large energy band gap of metal oxides, TPVs have a clear transmittance (43%) and good color coordinates, which ensure degrees of freedom to adopt TPV power generators in various colored structures or transparent power windows. The bidirectional feature of TPVs is ultimately desirable to maximize light utilization. TPVs can generate electric power from sunlight during the day and can also work from artificial light sources at night. In the near future, humans will acquire electric power without losing visibility with on-site energy supply platforms

Highly Transparent Bidirectional Transparent Photovoltaics for On-Site Power Generators

If we can transparently produce energy, we may apply invisible power generators to residential architectures to supply energy without losing visibility. Transparent photovoltaic cells (TPVs) are a transparent solar technology that transmits visible light while absorbing the invisible short wavelengths, such as ultraviolet. Installing TPVs in buildings provides an on-site energy supply platform as a window-embedded power generator or color-matched solar cell installation on a building surface. The record-high power generation (10.82 mW) and photocurrent value (68.25 mA) were achieved from large-scale TPVs (25 cm2). The metal oxide heterojunction is the fundamental TPV structure. The high-performance TPVs were achieved by adopting a thin Si film between ZnO and NiO as a functional light-absorbing layer. Based on the large energy band gap of metal oxides, TPVs have a clear transmittance (43%) and good color coordinates, which ensure degrees of freedom to adopt TPV power generators in various colored structures or transparent power windows. The bidirectional feature of TPVs is ultimately desirable to maximize light utilization. TPVs can generate electric power from sunlight during the day and can also work from artificial light sources at night. In the near future, humans will acquire electric power without losing visibility with on-site energy supply platforms

Highly Transparent Bidirectional Transparent Photovoltaics for On-Site Power Generators

If we can transparently produce energy, we may apply invisible power generators to residential architectures to supply energy without losing visibility. Transparent photovoltaic cells (TPVs) are a transparent solar technology that transmits visible light while absorbing the invisible short wavelengths, such as ultraviolet. Installing TPVs in buildings provides an on-site energy supply platform as a window-embedded power generator or color-matched solar cell installation on a building surface. The record-high power generation (10.82 mW) and photocurrent value (68.25 mA) were achieved from large-scale TPVs (25 cm2). The metal oxide heterojunction is the fundamental TPV structure. The high-performance TPVs were achieved by adopting a thin Si film between ZnO and NiO as a functional light-absorbing layer. Based on the large energy band gap of metal oxides, TPVs have a clear transmittance (43%) and good color coordinates, which ensure degrees of freedom to adopt TPV power generators in various colored structures or transparent power windows. The bidirectional feature of TPVs is ultimately desirable to maximize light utilization. TPVs can generate electric power from sunlight during the day and can also work from artificial light sources at night. In the near future, humans will acquire electric power without losing visibility with on-site energy supply platforms

Thermally Stable Silver Nanowires-Embedding Metal Oxide for Schottky Junction Solar Cells

Thermally stable silver nanowires (AgNWs)-embedding metal oxide was applied for Schottky junction solar cells without an intentional doping process in Si. A large scale (100 mm²) Schottky solar cell showed a power conversion efficiency of 6.1% under standard illumination, and 8.3% under diffused illumination conditions which is the highest efficiency for AgNWs-involved Schottky junction Si solar cells. Indium–tin–oxide (ITO)-capped AgNWs showed excellent thermal stability with no deformation at 500 °C. The top ITO layer grew in a cylindrical shape along the AgNWs, forming a teardrop shape. The design of ITO/AgNWs/ITO layers is optically beneficial because the AgNWs generate plasmonic photons, due to the AgNWs. Electrical investigations were performed by Mott–Schottky and impedance spectroscopy to reveal the formation of a single space charge region at the interface between Si and AgNWs-embedding ITO layer. We propose a route to design the thermally stable AgNWs for photoelectric device applications with investigation of the optical and electrical aspects