Dye-sensitized solar cells (DSCs) have been commonly used as photoenergy converters in hybrid photorechargeable systems due to their various advantages, especially high performance at low light intensity. Nevertheless, it is still unclear which factors influence the performance of DSC-combined energy storage devices. However, in low light conditions (1.37 W m−2, 410 lux), Cu+/+2(dmp)2 showed the highest Estored, corresponding to 8.8% of the total photoenergy conversion/storage efficiency (ηtotal).
The trend of ηoverall dim lighting indicates that output voltage is gradually becoming more influential for Estored. These findings indicate what factors we should consider in developing the indoor customized photo-rechargeable system.
Introduction
Motivation
Over 80% of commercial PV cells for outdoor deployment are based on silicon-based crystalline cells, classified as first-generation PV cells. Second-generation PV cells, a variety of thin-film solar cells have been rapidly developed, namely cadmium telluride (CdTe) and copper indium gallium (di)selenide (CIGS). During the last decades, a great deal of effort has been devoted to the development of third-generation PVs.
According to the photoactive materials and operating principle, they can be classified into organic (or polymer) solar cells, quantum dot solar cells, dye-sensitized solar cells, and perovskite solar cells. Compared to old-fashioned PVs based on the p-n junction, they incorporate a multilayer structure in which carriers are exchanged, so they are not subject to the theoretical Shockley-Queisser limit.
Dye-sensitized Solar Cells (DSCs)
- Structure and Working Principle
- Research Strategy
During the operation, a number of charge losses occur through different routes, mainly via charge recombination between the photoinjected electrons and the oxidized dye molecules (10−4s) or oxidized redox mediators, i.e. I3─in the electrolyte (10−2s). 16. For this reason, the building energy management systems (BEMS) industry is expected to grow to a size of approximately $1.5 billion (Figure 1.3), making customized ubiquitous indoor power supplies increasingly necessary.10, 17 -18Figure 1.3 schematically shows BEMS which requires so many types of sensors for monitoring the internal condition and obtaining the information. As mentioned above, photo energy can be converted directly into electrical energy through a PV system, but all types of PV are not suitable for indoor environments.
Moreover, (6) VOCof DSCs are easily controllable compared to other types of PV by controlling charge regenerator in the electrolyte. For those reasons, thin TiO2 film-based DSCs should be a promising future research theme to realize indoor tailored PV.
Hybrid Photo-rechargeable Systems
Experimental Methods
DSCs Fabrication
Characterization Techniques
- Current-Voltage (J-V) Measurement
- Incident Photon-to-Current Conversion Efficiency (IPCE)
- Controlled Intensity Modulated Photo Spectroscopy (CIMPS)
- Electrochemical Impedance Spectroscopy (EIS)
Conclusion
Experimental Section
Control and Monitoring of Dye Distribution in Mesoporous TiO 2 Film for Improving
Introduction
Results and Discussion
Conclusion
Experimental Section
Light Intensity Dependent Photo-energy Conversion/Storage Efficiency of Dye-sensitized Solar
Introduction
Over the past decades, there have been many projects about the future depletion of natural resources and the increasing greenhouse effect, and attempts to develop various renewable energy technologies.1-3 In addition, the effective power management enables us to have a large amount of surplus energy. For this reason, building energy management system industries are growing rapidly so that indoor environment-tailored ubiquitous power sources are increasingly needed. 4-6 With indoor lighting as an open and cheap power source, photo-rechargeable batteries (PCBs) are promising systems as indoor power supplier due to simultaneous photo-energy -conversion and storage.7-11 For application to indoor environment, photovoltaic part in PCB must meet the following requirements: (1) efficient conversion of indoor lighting power, (2) impervious to incident lighting conditions, (3) aesthetic impression, and (4) ) flexibly controllable open circuit voltage. Dye-sensitized solar cells (DSCs) certainly meet all requirements, so we adopted DSC as a photo-energy converter in PCB.12-16.
As the counterpart for energy storage, many types of supercapacitors have been used due to their high power density17-27, but have intrinsic problems such as low energy density and fast self-discharge.28 Lithium ion batteries (LIBs) have been proposed as an alternative energy storage part due to high energy density and long cycle life. However, any photovoltaic cells in a single unit cannot meet their high operating voltage (generally > 3 V), which requires tandem structural photovoltaic part. system photovoltaic cell pack and LIB are separated and wire-connected.30 Moreover, most active materials for LIB have significantly positive Li+ ion active potential (more than 4 VLi+/LiB corresponding to 1 V vs. normal hydrogen electrode, NHE), so it is difficult to sufficiently output voltage (VdCh) in combination with any photovoltaic electrodes. In this work, we developed the photo-rechargeable all-in-one dye-sensitized solar battery (DSSB) using thin graphite layer-coated lithium manganese oxide (LiMn2O4) as the electrode-immobilized storage material.
In general, 3 VLi+/Liregion is relatively inactive, but the introduction of thin graphitic shells enables good Li+ion reactivity in 3 VLi+/Liregion.34 Unlike 4 VLi+/Liregion, it is convenient to make VdCh which is defined as a potential gap redox between the charge regenerator. and storage materials. This modified LiMn2O4 storage electrode was combined with dye-sensitized TiO2 photoelectrode to realize a power-free all-in-one external PCB. We introduced three types of redox mediators as charge regenerators for the oxidized dye such as I−/I3−, Co2+/3+(bpy)3(PF6)2/3 and Cu+/2+(dmp)2TFSI1/2 and investigated the influence of of their electrochemical kinetics in the photo-charge/discharge performance depending on the light intensity.
As for standard light intensity (1 sol, 1000 W m−2), the regeneration ability of the redox mediator determined photocharge current density (JCh) and thus stored energy density (Estored) instead of VdCh. However, when photocharged under dim lighting close to indoor lighting, all charge regenerators yielded similar JCh. As a result, the overall photoenergy conversion/storage efficiency (ηtotal) was mainly determined by VdCh instead of JCh.
Results and Discussion
I−/I3− shows the highest photocharging capacity (QCh) corresponding to the gross area under the JCh time curve for 5 min, followed by Co2+/3+(bpy)3 and Cu+/2+(dmp) 2. To explain the overall η trend we observed photocharge and galvanostatic discharge profiles (Figure 5.5c -5.5h). Performance data for DSSBs under low illumination and light intensity dependence of ηIP′peak, corresponding to Figures 5.5 and 5.5b.
To clearly understand the light intensity dependence of JChof DSSB, we measured light source frequency response of photo-charging current efficiency ( = ⁄ ) using controlled intensity modulated photospectroscopy (CIMPS) equipped with monochromatic light-emitting diode (503 nm), where IChis the photo-charging current .64 Corresponding maximum values (ηIP′peak) of ηIP are summarized in Figure 5.5b and Table 5.3. We notice that the difference of ηIP′ peak between charge regenerators gradually becomes negligible as light intensity decreases. In contrast, the similar ηIP′ peak values under 0.6 W m−2or intensity (240 lux) are observed for all charge regenerators, which means the similar JCh.
The light intensity dependence of ηIP For fundamental insight into the light intensity dependence of photocharging current, we observed light source frequency response of photocharging current efficiency ( = ⁄ ) according to the light intensity using controlled intensity modulated photospectroscopy (CIMPS) equipped with monochromatic light emitting diode (503 nm).64 Figure 5.12a shows the real (ηIP′) and imaginary (ηIP′′) parts of photo-charge current efficiency frequency response at 72.8 W m−2 of intensity. As expected, I─/I3─ provides the highest ηIP′ peak (ηIP′peak) and is followed by Co2+/3+(bpy)3and Cu+/2+(dmp)2, which trend is consistent with the photo-charge current density (JCh) order. Briefly, it is logical inference that ηIP′ peak and frequency-dependent ηIP′ decay are related to charge injection and charge diffusion in the PE, respectively.
This section focuses on the correlation between the ηIP′ decay and the effective charge diffusion coefficient (Dn). DSSBs based on I─/I3─ show the largest decay of ηIP' but negligible decay of ηIP' under an intensity of 3.3 W m−2. We calculated the ratio of the minimum ηIP′ to the maximum ηIP′ to compare the frequency-dependent decay rate of ηIP′ as follows, where δIP is the frequency-dependent decay factor of ηIP′, ηIP′ is the static ηIP′ at the lowest frequency (10− 1Hz), and ηIP′ the maximum value is ηIP′ at the cut-off frequency.
Conclusion
Experimental Section
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J; Ko, J., Graphene nanoplatelets doped with N at the edges as metal-free cathodes for organic dye-sensitive solar cells. Hao, Y.; Yang, W.; Zhang, L.; Jiang, R.; Mijangos, E.; Saygili, Y.; Hammarstrom, L.; Hagfeldt, A.; Boschloo, G., A small electron donor in cobalt complex electrolyte significantly improves efficiency in dye-sensitive solar cells. Visser, A.; Peter, L.; Ponomarev, E.; Walker, A.; Wijayantha, K., Intensity dependence of electron backreaction and transport in dye-sensitized nanocrystalline TiO2 solar cells.
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