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

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

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

Silver-Nanowire-Embedded Transparent Metal-Oxide Heterojunction Schottky Photodetector

We report a self-biased and transparent Cu₄O₃/TiO₂ heterojunction for ultraviolet photodetection. The dynamic photoresponse improved 8.5 × 10⁴% by adding silver nanowires (AgNWs) Schottky contact and maintaining 39% transparency. The current density–voltage characteristics revealed a strong interfacial electric field, responsible for zero-bias operation. In addition, the dynamic photoresponse measurement endorsed the effective holes collection by embedded-AgNWs network, leading to fast rise and fall time of 0.439 and 0.423 ms, respectively. Similarly, a drastic improvement in responsivity and detectivity of 187.5 mAW^–1 and of 5.13 × 10⁹ Jones, is observed, respectively. The AgNWs employed as contact electrode can ensure high-performance for transparent and flexible optoelectronic applications

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

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

Compliance-Free Multileveled Resistive Switching in a Transparent 2D Perovskite for Neuromorphic Computing

We demonstrate the pulsed voltage tunable multileveled resistive switching (RS) across a promising transparent energy material of (C₄H₉NH₃)₂PbBr₄. The X-ray diffraction and scanning electron microscopy results confirm the growth of (001) plane-orientated nanostructures of (C₄H₉NH₃)₂PbBr₄ with an average size of ∼360 nm. The device depicts optical transmittance higher than 70% in the visible region and efficient absorbance in the ultraviolet region. The current–voltage measurement shows the bipolar RS. In addition, depending on the magnitude of applied electric pulse, the current across the device can be flipped in four different levels, which remain stable for long time, indicating multimode RS. Further, the current across the device increases gradually by applying continuous pulses, similar to the biological synapses. The observed results are attributed to the electric field-induced ionic migration across the (C₄H₉NH₃)₂PbBr₄. The existing study should open a new avenue to apply this promising energy material of perovskite for multifunctional advanced devices

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

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