Noble metals-TiO2 nanocomposites: From fundamental mechanisms to photocatalysis, surface enhanced Raman scattering and antibacterial applications

The origins of recombination processes, particularly those that relate to current–voltage hysteresis, are still unclear in perovskite solar cells. Of particular interest is the impact different contact materials have on the level of hysteresis observed. This work shows that there is a clear link between ionic movement and interfacial recombination, which have both been shown to be responsible for hysteresis. When low-temperature transient photovoltage (TPV) measurements are performed over a period in which ions redistribute within the perovskite layer, the dominant recombination mechanism, responsible for hysteresis and other slow dynamic processes, is found to occur at the TiO2/perovskite interface. We observe an anomalous negative transient upon firing the laser pulse, which we attribute to interfacial recombination at the TiO2/perovskite interface. The impact of recombination at the perovskite/HTL interface is shown to be negligible by performing TPV measurements using different laser wavelengths to pr...

/pdf/ionic-influences-on-recombination-in-perovskite-solar-cells-4n5z9y4zqq.pdf

Ionic Influences on Recombination in Perovskite Solar Cells

Indoor photovoltaics (IPVs), which convert the indoor light energy into direct electricity, have attracted research attention due to their potential use as an excellent amicable solution of sustainable power source to drive low-power-needed sensors for the internet of things (IoT) applications. Our daily life adopts various indoor light sources, such as indirect sunlight, incandescent lamps, halogen lamps, fluorescent lamps, and LED bulbs, that typically deliver lower light intensity (200–1000 lux) as compared to that of sun light (∼100,000 lx). In this review, we firstly classified the indoor lights depending on their working mechanism and resulting emission spectrum. Because the indoor light intensities are rather low that may lead to overestimate/underestimate the power conversion efficiency (PCE) of IPV devices, then, the cautious points for correctly measuring the indoor light intensity as well as the device characteristics are summarized. Several light sources with various light intensities are reported so far, but for lack of common or standard calibration meter that induces a ambiguity in PCE determination, so we suggest/propose to use a universal LED lux meter with NIST-traceable calibration (e.g. Extech LT40-NIST) and also recommended the device results are expressed in maximum power point Pmax along with PCE values. It is generally believed that the materials play key roles on the performance of the IPV devices. Since the indoor light intensity is much weaker as compared to that of outdoor irradiation, the typical inferior photo-stability of organic materials under sunlight may not be as crucial as we considered to harvest indoor light energy, opening a great room for organic IPV material developments. In principle, all materials for outdoor PVs may also be useful for IPVs, but the fundamental material requirement for IPVs which needs sufficiently covering the absorption range between the 350–700 nm with high molar extinction coefficient should be primarily concerned. In order to get the thorough knowledge of materials for achieving better efficient IPVs, the reported IPVs were collected and summarized. According to these reports, the materials utilized for IPVs have been classified into two major groups, inorganic and organic materials, then divided them into several sub-classes, including (1) silicon and III-V semiconductor photovoltaics, (2) dye-sensitized photovoltaics, (3) organic photovoltaics, and (4) perovskite-based photovoltaics, depend on their structural nature and device working principle. For every individual class, the structure-property-efficiency relationship of the materials was analyzed together with the highlights on the best efficiency material, challenge and perspective. For inorganic IPV materials, III-V semiconductor GaAs-based IPVs performed a very impressive PCE (28%). For dye sensitizers, there are more flexible strategies to modulate the absorption profiles of organic materials. A high efficiency dye-sensitized solar cell (DSSC)-based IPV with a PCE up to 32% has been successfully realized with co-sensitized dyes. For organic solar cell (OSC)-based IPVs, fullerene-based acceptors are advantageous for their well-matching desired absorption range and superior electron transport features. A recent OSC-based IPV with the active layer composed of dithienobenzene-based donor and fullerene acceptor was reported to deliver a PCE of 28%. Among these emerging photovoltaic materials, it is no doubt that perovskites (e.g. CH3NH3PbI3) are superior for solar energy conversion due to the crystallinity for good charge transport, better spectral coverage and the low exciton binding energy. Until very recent, a perovskite-based IPV with a PCE of 35% was reported with good stability by the incorporation of an ionic liquid for effectively passivating the surface of the perovskite film, indicating the bright prospect of perovskite for IPV application. Overall, the review on these reports implies the essential criteria of materials suitable for IPVs that may trigger new ideas for developing future champion materials for various devices and the realization of practical IPV applications.

Device characteristics and material developments of indoor photovoltaic devices

The status and problems of upscaling research on perovskite solar cells, which must be addressed for commercialization efforts to be successful, are investigated. An 804 cm2 perovskite solar module has been reported with 17.9% efficiency, which is significantly lower than the champion perovskite solar cell efficiency of 25.2% reported for a 0.09 cm2 aperture area. For the realization of upscaling high-quality perovskite solar cells, the upscaling and development history of conventional silicon, copper indium gallium sulfur/selenide and CdTe solar cells, which are already commercialized with modules of sizes up to ≈25 000 cm2 , are reviewed. GaAs, organic, dye-sensitized solar cells and perovskite/silicon tandem solar cells are also reviewed. The similarities of the operating mechanisms between the various solar cells and the origin of different development pathway are investigated, and the ideal upscaling direction of perovskite solar cells is subsequently proposed. It is believed that lessons learned from the historical analysis of various solar cells provide a fundamental diagnosis of relative and absolute development status of perovskite solar cells. The unique perspective proposed here can pave the way toward the upscaling of perovskite solar cells.

Historical Analysis of High-Efficiency, Large-Area Solar Cells: Toward Upscaling of Perovskite Solar Cells

The Internet of things (IoT) has been rapidly growing in the past few years. IoT connects numerous devices, such as wireless sensors, actuators, and wearable devices, to optimize and monitor daily activities. Most of these devices require power in the microwatt range and operate indoors. To this end, a self-sustainable power source, such as a photovoltaic (PV) cell, which can harvest low-intensity indoor light, is appropriate. Recently, the development of highly efficient PV cells for indoor applications has attracted tremendous attention. Therefore, different types of PV materials, such as inorganic, dye-sensitized, organic, and perovskite materials, have been employed for harvesting low-intensity indoor light energy. Although considerable efforts have been made by researchers to develop low-cost, stable, and efficient PV cells for indoor applications, Extensive investigation is necessary to resolve some critical issues concerning PV cells, such as environmental stability, lifetime, large-area fabrication, mechanical flexibility, and production cost. To address these issues, a systematic review of these aspects will be highly useful to the research community. This study discusses the current status of the development of indoor PV cells based on previous reports. First, we have provided relevant background information. Then, we have described the different indoor light sources, and subsequently critically reviewed previous reports regarding indoor solar cells based on different active materials such as inorganic, dye-sensitized, organic, and perovskite. Finally, we have placed an attempt to provide insight into factors needed to further improve the feasibility of PV technology for indoor applications.

Solar Cells for Indoor Applications: Progress and Development.

Pseudo-Halide Perovskite Solar Cells

In this study, we investigated the characteristics of perovskite solar cells under low illuminance condition for indoor application of perovskite solar cells. The open-circuit voltage remained around 70% at 0.1% illuminance of AM1.5. This result indicates the potential for indoor application of perovskite solar cells.

Characteristics of perovskite solar cells under low illuminance condition

Halide perovskite for low-power consumption neuromorphic devices

The fabrication of highly efficient nickel oxide (NiOx) thin film for optoelectronic devices is a challenging task because optoelectronic properties are considerably influenced by deposition technique and film thickness. The effect of thickness on the film properties of electron beam–physical vapour-deposited NiOx thin film has been investigated in this work. The influence of post-annealing treatment on the optoelectronic properties of the film was compared with that of the as-deposited one. Optical transparency gradually decreased upon the successive increment in thickness of the as-deposited and annealed films. The surface roughness of as-deposited films increased linearly with the increase in film thickness, but this behaviour was altered in post-annealed films. Spherical grains with high packing density were observed on the as-deposited films, but the grain size was altered substantially on the post-annealed films. The annealed films presented a higher work function than their corresponding as-deposited films. This work presents important insights into the design of photovoltaic devices with an effective deposition process, including a high material utilisation. Moreover, an attempt of fabricating inverted perovskite solar cell on as-deposited and annealing NiOx film as hole transporting material exhibited power conversion efficiency of 11.98% and 12.28%, individually. It was noticed that the high temperature annealing on NiOx film had a very little impact on the comparative photovoltaic performance of aforementioned PSC devices.

Optoelectronic Properties of Electron Beam-Deposited NiOx Thin Films for Solar Cell Application

Perovskite/crystalline silicon tandem structures have attracted much attention as promising high-efficiency solar cells. To achieve higher efficiencies, a method of depositing perovskite films on textured substrates is required. In this work, we established the process of fabricating perovskite films by sputtering. Sputter-processed perovskite films showed characteristics similar to those of their solution-processed counterparts. In addition, a power conversion efficiency of 1.84% was attained from solar cells employing sputter-processed films. Moreover, it was confirmed that homogeneous films can be obtained even on substrates with significant roughness. Our results indicate that sputtering is a promising method of achieving high-efficiency tandem cells.

https://iopscience.iop.org/article/10.7567/APEX.10.094101/pdf

Itaru Raifuku

Papers

Pseudo-Halide Perovskite Solar Cells

Characteristics of perovskite solar cells under low illuminance condition

Halide perovskite for low-power consumption neuromorphic devices

Optoelectronic Properties of Electron Beam-Deposited NiOx Thin Films for Solar Cell Application

Fabrication of perovskite solar cells using sputter-processed CH3NH3PbI3 films