Cesium Lead Halide Inorganic-Based Perovskite-Sensitized Solar

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Cesium Lead Halide Inorganic-Based Perovskite-Sensitized Solar Cell for Photo-Supercapacitor Application Under High Humidity Condition Chi Huey Ng, Hong-Ngee Lim, Shuzi Hayase, Zulkarnain Zainal, Suhaidi Shafie, Hing Wah Lee, and Nay Ming Huang ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.7b00103 • Publication Date (Web): 02 Jan 2018 Downloaded from http://pubs.acs.org on January 2, 2018

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ACS Applied Energy Materials

Cesium Lead Halide Inorganic-Based Perovskite-Sensitized Solar Cell for PhotoSupercapacitor Application Under High Humidity Condition Chi Huey Nga,c, Hong Ngee Lim*a,b, Shuzi Hayasec, Zulkarnain Zainala, Suhaidi Shafied, Hing Wah Leee and Nay Ming Huangf a

Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia. b

Materials Synthesis and Characterization Laboratory, Institute of Advanced Technology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.

c

Graduate School of Life Science and Systems Engineering, Kyushu Institute of Technology, 2-4 Hibikino, Wakamatsu-ku, Kitakyushu 808-0196, Japan.

d

Department of Electrical and Electronic Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.

e

Nanoelectronics Lab, MIMOS Berhad, Technology Park Malaysia, Kuala Lumpur 57000, Malaysia.

f

New Energy Science & Engineering Programme, University of Xiamen Malaysia, Jalan SunSuria, Bandar SunSuria, 43900 Sepang, Selangor Darul Ehsan, Malaysia. *

Address correspondence to (H.N. Lim) [email protected]

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Abstract In shaping a clean and green energy environment, the installation of a self-rechargeable supercapacitor in an electric vehicle has the goal of decreasing the emission of unwanted gases, which can be realized by adopting a perovskite solar cell for self-charging the supercapacitor. In this work, a CsPbBr2.9I0.1 perovskite-sensitized solar cell is integrated for the first time with an asymmetrical supercapacitor for a photo-supercapacitor application. Prior to this integration, the performances of the perovskite-sensitized solar cell and supercapacitor are individually examined. The perovskite-sensitized solar cell displays a good efficiency, with the ability to retain 70% of its efficiency after a week of storage in a dark humidity-controlled desiccator and 33% of its efficiency under UV and air exposure at a high relative humidity of more than 80% for 24 h. The asymmetrical supercapacitor exhibits a high areal capacitance of 150 mFcm-2 with a capacitance loss of only 4% after continuous cyclic performances, which shows its potential for the photo-supercapacitor application. The photo-supercapacitor device is sensitive to light, with the photovoltage and photocurrent plunging to zero in the absence of light, and provides an areal capacitance of 30 mFcm-2. It thus unlocks opportunities for photo-supercapacitor applications in line with green energy development. Keywords: perovskite sensitized solar cell, supercapacitor, photo-supercapacitor, humidity, stability


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1.

Introduction

The continuous growth of environmental concerns and energy demands has made it urgent to supply clean energy to shape a clean and green energy environment. Energy waste and pollution could be partly mitigated if the energy-based appliances that humans rely on could be made eco-friendly. As an example, a supercapacitor electric bus, which just needs 10 s to fully charge the supercapacitor, was adopted in China and is an advancement in alleviating environmental issues.1 Nevertheless, the installation of a pantograph on each electric bus and the construction of stop stations are still considered to be economically unfriendly moves. Dye-sensitized solar cell (DSSC), which is the third generation of solar cell has attracted considerable attention for solar powered application owing to its considerable efficiency, lower materials and manufacturing costs. Evidently, a photo-supercapacitor composed of titania and carbonized porous silicon wafer DSSC has attained high power conversion efficiency of 4.8% and an overall efficiency of 2.1% when the DSSC was coupled to a supercapacitor.2-3 Additionally, a solid state integrated dye-sensitized photoelectric conversion and carbon nanotube-based energy storage device presented high photoconversion and storage efficiency of 5.12%.4 Though the DSSC possesses considerable efficiency, however, leakage of electrolyte restrains the progression of DSSC for practical applications. In addition, most DSSC-based photo-supercapacitor suffered from low charging voltage and low energy density performances. Specifically, in an ideal case, the charging voltage of an energy storage device for a photo-supercapacitor should equal to the opencircuit voltage of a solar cell. Hence, the incorporation of a low open circuit voltage DSSC (up to a maximum voltage of 0.8 V) restrained the energy density performance of the supercapacitor and overall, it reduced the performance of the photo-supercapacitor.5 With the rapid progression of perovskite solar cells, typically methylammonium lead halide (MAPbI3), it possesses excellent optical and electronic properties, additionally has been reported as a



good light absorbing material over the entire visible solar spectrum.6 In 2015, a photosupercapacitor composed of MAPbI3 perovskite solar cell and lithium ion battery reported with a high overall photo-electric conversion and storage efficiency of 7.8%.7 In subsequent year, a maximum efficiency of 4.7% and high energy storage efficiency of 73.77% was reported for a MAPbI3 perovskite solar cell integrated photo-supercapacitor.8 The high power conversion efficiency of the solar cell enables the converter energy to be stored in a supercapacitor. Herein, the integration of a perovskite solar cell and a supercapacitor makes it possible to fully utilize solar energy to recharge the supercapacitor. Generally, energy conversion and storage devices have been operated independently by connecting external wires, and only a single photo-supercapacitor device has been reported. The first CH3NH3PbI3 perovskite-based solar cell-polypyrrole supercapacitor connected in a series power backup system was successfully presented in 2015, with an overall conversion efficiency of 10% for the combined system.9 Nevertheless, the loss of power and energy has further prompted the integration of a photovoltaic device and supercapacitor into a single device, with the goal of reducing its internal resistance by 43%.10 An advancement was made by photo-supercapacitor when a singly integrated CH3NH3PbI3PEDOT-modified printable perovskite solar cell exhibited a maximum overall efficiency of 4.70%, with a high energy storage efficiency of 73.77%.8 So far, most of the reported photosupercapacitor studies have utilized a dye-sensitized solar cell as the energy conversion part, and few reports on perovskite solar cells have been reported. However, the perovskite solar cell has the potential to serve as the largest energy production device in the near future because of its superb solar harvesting ability, which is on par with that of a silicon wafer solar cell. Nevertheless, thus far, its long-term stability (typically the methylammonium lead iodide perovskite material) performance has been the main barricade for commercialization. In 2015, a study that utilized an inorganic cesium cation, replacing the organic perovskite cation,


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revealed an improved stability performance,11 even after the cells were stored for 2 weeks in a dry air atmosphere (relative humidity (RH) 15–20%) and dark condition.12 In this work, a cesium-based perovskite-sensitized solar cell was successfully fabricated under an ambient condition (RH >80%) without any encapsulation and integrated with an asymmetric supercapacitor for the first time, without the connection of external wires. To date, the cesium-based perovskite solar cell is the first solar cell to be used for a photosupercapacitor application. This work mainly focused on the fundamental study of the performances of a series of mixed halide cesium-based perovskite-sensitized solar cells (CsPbBr3-xIx) under the influence of high humidity (>80% RH) and investigated the possibility of adopting it as a photo-supercapacitor device. 2.

Results and discussion Figure 1 shows images of the as-synthesized yellowish cesium-based perovskite-

sensitized solar cells fabricated under ambient conditions. The complete cell is composed of the compact and mesoporous TiO2, CsPbBr3-xIx perovskite material, and Spiro-OMeTAD as the HTM. The surface morphologies and cross section of the perovskite-sensitized solar cell are shown in Figure 2. The cross section of the solar cell (Figure 2a) is composed of compact and mesoporous TiO2 layers, perovskite materials, and Spiro-OMeTAD as the HTM. According to Figure 2a, the perovskite and mesoporous TiO2 interfaces are indistinguishable. It is theorized that the pores of the mesoporous TiO2 are fully filled with the CsPbBr3-xIx perovskite materials. Figure 2b–e sequentially show the top view morphological surface of the spun-coated CsPbBr3, CsPbBr2.9I0.1, CsPbBr2.8I0.2, and CsPbBr2.7I0.3. The presence of tiny voids (darker pits) as observed in Figure 2b could be the result of the evaporation of organic solvent during the thermal annealing process. The non-pinhole-free perovskite film was prone to the degradation of the perovskite-sensitized solar cell.13-14 Interestingly, the addition of a



small amount of iodide subtly changed the surface morphology of the solar cell. As the concentration of iodide increased, the compactness of the perovskite film improved. Figure 2c shows that the pits were partially covered by the growth of perovskite, and the crystallinity of the perovskite grains was improved. At a higher concentration of iodide (x = 0.2 and 0.3), the complete coverage and compact perovskite surface were presented, as illustrated in Figures 2d and 2e. The magnified FESEM images showing the coverage of the voids by the perovskite grains with the increase in the iodide concentration are included in Figure S1 for clarification purposes. The XRD patterns of the cubic phase CsPbBr3-xIx perovskite materials in Figure S2 show crystalline peaks at 15.2°, 21.6°, and 30.6°, which are indexed to (100), (110), and (200). An unnoticeable blue-shift in XRD peaks to lower angles as the iodide concentration increased indicates the substitution of iodide ions over the bromide matrix.15 The J-V and stability performances of each perovskite-sensitized solar cell were determined to investigate the performances and rate of degradation of the solar cells in an ambient environment. The power conversion efficiencies (PCE) of CsPbBr3-xIx perovskitesensitized solar cells that incorporated PEDOT:PSS counter electrodes were investigated, because this is the system that would be employed for the photo-supercapacitor. The J-V performance of the CsPbBr3-xIx solar cell is shown in Figure 3a. The Voc and FF of all the solar cells were constantly maintained at 0.6 V and 30%, respectively. Consequently, the PCE was solely dependent on the short circuit current density (Jsc). The champion CsPbBr2.9I0.1 cell exhibited a high Voc of 0.67 V, FF of 31%, and Jsc of 2.2 mAcm-2, with a PCE of 0.46%. The low efficiency obtained in our work compared to those reported in other studies could have been due to the dissimilar fabrication method, non-optimal thickness of the TiO2 layers, and minor degradation of the precursors or perovskite materials in the highly humid environment. Nevertheless, it should be mentioned that it would be very feasible to fabricate low-cost perovskite-sensitized solar cells under a high humidity condition, without


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any encapsulating layer over the active materials for the installation or incorporation of a perovskite solar cell in multiple applications, once the stability issue is solved. Figure 3b illustrates the electrochemical impedance of the perovskite-sensitized solar cell. The radius of the semicircle corresponds to the internal resistances of the TiO2/perovskite interface, TiO2 layer, and ITO/TiO2 interface.16 The CsPbBr2.9I0.1 device presents the smallest semicircle, indicating the smallest internal resistance, compared to the devices with other molar ratios. The internal resistance of each device increases (larger semicircle) as the iodide concentration increases. A Bode plot is presented in Figure 3c to investigate the electron lifetimes (ɽe) of the CsPbBr3-xIx perovskite materials, where x = 0, 0.1, 0.2, and 0.3. The frequency peaks of the Bode plot correspond to the charge transfer values of the light-harvesting materials. It shows that the frequency peak shifted to a lower frequency region upon the incorporation of a small amount of iodide (x = 0.1), which implied a longer electron lifetime (4842 µs). In good agreement with the results shown in Figure 3b, the addition of a minute amount of iodide successfully prolonged the electron lifetime, which decelerated the recombination process and showed the positive effect of the iodide inclusion by improving the surface coverage of the perovskite film. As depicted in Table S1, the electron lifetimes of CsPbBr2.7I0.3 is eightfold shorter than that of CsPbBr2.9I0.1, implying that the inclusion of a larger amount of iodide ions altered the morphological structure of the perovskite film, which is in agreement with the FESEM images (Figure 2), and consequently impeded the transportation of charges. In addition, it proved that the addition of an optimum amount of iodide enhanced the charge transport and reduced the resistivity performance, which contributed to longer electron lifetimes.17 The degradation and decomposition of perovskite upon exposure to UV, air, and water are inevitable. To date, the stability of the perovskite solar cell is the most important factor to consider for further practical applications. This work also investigated the long-term



stability of the perovskite-sensitized solar cell, as shown in Figure 3d–g. The insertion of the optimized amount of iodide not only contributes to the PCE performance, but also improves the morphological formation with a pinhole-free perovskite surface, and thus retards the degradation process (>64% efficiency was retained after 168 h). The advantage of using a cesium-based material such as CsPbBr3 for the sensitized solar cell was that it retained 81% of its original PCE upon storage for 168 h, compared to the 64%–76% PCE retention for iodide-incorporated solar cells. The stability of the perovskite films was highly dependent on the iodide concentration, where a higher iodide concentration exaggerated the degradation process. The retarded degradation phenomenon could be due to the self-degradation of the iodide-based perovskite solar cell, wherein when it was exposed to air, light illumination, and an electric field, the initial degradation of the perovskite layer induced the generation of the I2 product. Concurrently, the high vapor pressure of I2 at room temperature is expected to diffuse to the non-degraded perovskite region and exacerbate the perovskite film.18 Additionally, the degradation of perovskite could be also due to the UV factor. Based on the stability profiles, the Jsc fluctuation and PCE performances might be ascribed to the initial UV degradation of the perovskite film. The abrupt decrease in Jsc during the first 48 h was due to the presence of traps, which prevented electron extraction. In the next few hours, the Jsc performance bounced back as a result of the generation of PbI2 which could then passivate the recombination sites and improve the carrier extraction. Subsequently, a further degradation resulted in a PCE decrease.19 A further discussion on the beneficial effect of the degradation by the formation of the PbI2 by-product will be provided. The results of the stability investigation of the perovskite-sensitized solar cell stored under dark and humidity-controlled conditions are shown in Figure 3d–g. Next, the results of an in-depth stability investigation of the CsPbBr2.9I0.1 perovskite-sensitized solar cell under prolonged exposure to UV and moisture for 24 h (>80% RH) are presented in Figure 4a,


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which highlights the beneficial effect of adding an optimized amount of iodide. In comparison to the methylammonium lead halide perovskite material, the cesium lead halide perovskite material possesses much better stability, where 33% of the original PCE of CsPbBr2.9I0.1 was retained in comparison to the methylammonium-based solar cell stored in air, which retained less than 20% of its PCE after 24 h.20 The declining PCE of the CsPbBr2.9I0.1 sensitized solar cell was mainly attributed to the plunge in Jsc. Noticeably, the fluctuation of Voc was ascribed to the Voc value, which was only tuneable using the HOMO and LUMO levels of the HTM and titania. However, this was not the main target of our work. After 30 min of UV exposure in air, the abrupt increase in Jsc led to a 1.3-fold PCE increase in the first 30 min. This could have been due to the passivation effect of PbI2 which reduced the defect states and recombination sites at the perovskite grain boundary and the perovskite/TiO2 interface. The skyrocketed Voc and FF performance were evidence of trap passivation and the reduced recombination process, in good agreement with Figure 3c (longer electron lifetime). The PCE degradation process was retarded by the increasing FF and Voc.19 The continuous UV degradation prompted the generation of a greater PbI2 and the exposure to moisture thus gradually reduced the cell performance. The degradation phenomenon of the CsPbBr2.9I0.1 solar cell was very low because of the low iodide composition (x = 0.1) within the bromide scaffold. The digital photographic images of CsPbBr3-xIx perovskite devices before and after prolonged UV radiation and moisture exposure are illustrated in Figure S3 where the color change for the freshly prepared yellowish perovskite films implies the degradation of the perovskite materials. The hysteresis index (HI) of the CsPbBr2.9I0.1 perovskite-sensitized solar cell is depicted in Figure 4b and Figure S4. The HI was calculated according to Equation S4. It shows that a freshly prepared solar cell exhibited small HI of 0.099 and was slightly increases to 0.145 after 90 min UV and air exposure. The gradual increment of HI reflects that the inclusion of optimized amount of iodide (0.1 molar ratio)



mitigates the hysteretic effect. Hereafter, the HI values were continuously increasing (up to 0.44) as the UV and air exposure rate prolonged, consequently resulted in severe UV degradation, as aforementioned in Figure 4a. The outperforming CsPbBr2.9I0.1 perovskite-sensitized solar cell was chosen for the photo-supercapacitor application after the preliminary screening of the performance of mixed halide perovskite films. The performance of the asymmetric supercapacitor was examined before the integration occurred. A PEDOT:PSS-assisted RZCo positive supercapacitor electrode stacked with a PyR negative electrode, and utilizing LiClO4/acetronitrile as the electrolyte, was tested before being employed for the photo-supercapacitor application. The FESEM image of RZCo shows the growth of ZCo on the graphite sheet (Figure S5a). The presence of the Co3O4, ZnO, and reduced graphene oxide active materials was shown using RAMAN spectroscopy (Figure S5b) and the EDX spectrum (Figure S5c). The PEDOT:PSSassisted RZCo//PyR supercapacitor presents quasi-rectangular cyclic voltammograms (CV) at various scan rates, indicating ideal capacitive behavior and fast charging ability, as shown in Figure 5a. The areal capacitance calculated from CV (Figure 5b) increases as the scan rate decreases. This phenomenon is owing to adequate time for the electrolyte ions to intercalate and de-intercalate within the nanocomposite matrix. Figure 5c depicts the galvanostatic charge discharge of the PEDOT:PSS-assisted RZCo//PyR supercapacitor, where the slightly non-linear discharge curve (IR drop) indicates the presence of a Faradaic reaction and internal resistance. The prolong discharging time at a current density of 0.1 mAcm-2 contributed to an areal capacitance of 150 mFcm-2.21 Although the supercapacitor exhibited high capacitance, it had a high charge transfer (Rct) resistive performance, which could be attributed to the bulky electrode interface. Additionally, in relation to the conductivity of the electrolyte,22 the mildly conductive LiClO4/acetonitrile impeded the ease penetration of electrolyte ions across the hybrid matrix. In addition, the large Rct performance might have


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arisen from the activation barrier (kinetic regime) of the electrode and electrolyte interface, which limited the diffusion of charge-complexes.23 The supercapacitor (Figure 5e) showed 4% capacitance losses after 1000 continuous charge/discharge cycles and 12% capacitance losses after 2000 cycles (Figure S6). These minor capacitance losses were due to the deterioration of the active materials and degradation of polymer chains after the excessive swelling and shrinking process. The cesium-based perovskite-sensitized solar cell was first integrated to an asymmetric supercapacitor for a photo-supercapacitor device (Figure S7). The cesium perovskite-sensitized solar cell was stacked with a PEDOT:PSS cast shared intermediate cathode for the energy conversion part, while the positive electrode of PEDOT:PSS-assisted RZCo was coupled to a PyR negative electrode separated by LiClO4/acetronitrile soaked filter paper for the energy storage part. PEDOT can function as an electrode material because of its fast charge/discharge kinetics, low cost, and fast doping/dedoping process, and the addition of PSS is expected to be able to improve the conductivity of PEDOT:PSS.8,24 Fundamental studies and measurements such as the photovoltage and photocurrent responses were performed, as shown in Figures 6a and 6b, which show the positive effect toward light response. Based on Figure 6a, zero voltage was presented in the first 50 s without the illumination of light. Subsequently, in the presence of light, the photovoltage abruptly increased to ~80 mV and continued increasing to 90 mV for 100 s, after which it drastically decreased when the light was switched off. Likewise, the rapid increase in photocurrent upon light illumination of 0.16 mAcm-2, which subsequently decreased gradually over time, indicated the projection of photo-generated charges into the supercapacitor vicinity.25 During the discharge process, the sudden decrease in current showed that no current was generated in the absence of solar illumination, which proved that the charging of the supercapacitor was indeed the result of the light source. To further prove the energy conversion and storage of



the photo-supercapacitor, the photocharged integrated device was galvanostatically discharged in the dark at a current of 0.1 mA. As the integrated device reached the cut-off potential of 0.07 V, the discharge process occurred in the dark with only the supercapacitor’s electrodes connected (Figure 6c). The photo-supercapacitor exhibited an areal capacitance of 30 mFcm-2. 3.

Conclusion In conclusion, the utilization of an inorganic cesium-based perovskite material and the

beneficial effect of incorporating a minute amount of iodide into the bromide framework improved the film’s compactness and significantly improved the stability of a solar cell. A PCE of 70% was successfully retained after storage for a week in a humidity-controlled desiccator under a dark condition for the CsPbBr2.9I0.1 perovskite-sensitized solar cell. The stability of the CsPbBr2.9I0.1 device under UV and moisture (>80% RH) exposure was also investigated. The cesium-based lead halide sensitized solar cell stored in air could still retain 33% of its power conversion efficiency, which was 1.6-fold higher than a methylammoniumbased solar cell (which could only retain 20% of its efficiency) after 24 h. The addition of an optimized amount of iodide dramatically improved the electron lifetime of the CsPbBr2.9I0.1 perovskite-sensitized solar cell, which was 5-fold longer than that of a pure bromide perovskite material. The achievement of an inorganic based perovskite-sensitized solar cell at such a high humidity condition (>80% RH) prompted the integration with an asymmetric supercapacitor for a photo-supercapacitor application. This integrated device successively showed that photogenerated carriers were transferred and stored in the supercapacitor matrix. The photo-supercapacitor showed a positive effect toward light illumination. In contrast, the photovoltage and photocurrent abruptly decreased to zero when the light was switched off. Further optimization of the perovskite and electrode materials of the photo-supercapacitor,


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typically targeting the stability performance, will surely promote this novel device as a new generation green power back device.

4.

Experimental Section

Fabrication of cesium perovskite-sensitized photo-supercapacitor The fabrication of the photo-supercapacitor was carried out by integrating the champion solar cell, the CsPbBr2.9I0.1 perovskite-sensitized solar cell, and the asymmetric supercapacitor without the connection of external wires. Specifically, a photoanode composed of compact and mesoporous titania, the perovskite light harvesting material, and Spiro-OMeTAD as the HTM was coupled to a PEDOT:PSS-coated RZCo layer positive electrode and PyR negative electrode asymmetric supercapacitor, with 1 M LiClO4/acetonitrile used as the redox electrolyte. Clearly, the PEDOT:PSS-coated RZCo electrode served as the shared electrode for the solar cell and supercapacitor. The champion perovskite-sensitized solar cell (CsPbBr2.9I0.1) was sparked with a minute amount of the Spiro-OMeTAD electrolyte to improve the charge diffusivity before taking measurements. Supporting Information The tabulated electron lifetimes, hysteresis index, XRD, digital photographic images, and FESEM images of perovskite materials, FESEM image, RAMAN spectroscopy, and EDX spectrum of RZCo supercapacitor active materials, life cycle profile of RZCo supercapacitor, illustration of photo-supercapacitor, and additional experimental details are provided in Supporting Information. This material is available free of charge on the ACS Publications website. Author Information Corresponding Author



H.N. Lim Tel: +60 3 8946 7494 E-mail address: [email protected]

Acknowledgement All the authors contributed equally to this work. This work was supported by the Fundamental Research Grant Scheme (01-01-16-1872FR) from the Ministry of Higher Education of Malaysia and ASEAN-ROK Academic Exchange Programme 2016/2017. Notes The authors declare no conflict of interest. References 1.

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Figures and Figure Captions

Figure 1. Digital photographic image of as-fabricated CsPbBr3-xIx perovskite-sensitized solar cells where x = 0, 0.1, 0.2, and 0.3.

Figure 2. (a) Cross section of ITO/c-TiO2/m-TiO2/CsPbBr3-xIx/HTM and (b–e) top view surface morphology of ITO/CsPbBr3-xIx perovskite-sensitized solar cells with molar ratios of 0 (b), 0.1 (c), 0.2 (d), and 0.3 (e).



Figure 3. (a) J-V performances of CsPbBr3-xIx sensitized solar cell under 1 sun illumination and in dark, and (b) Nyquist plot and (c) Bode phase diagram of CsPbBr3-xIx sensitized solar 18 Environment ACS Paragon Plus

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cell under 1 sun illumination measured close to open-circuit voltage. The solar cells were measured under 1 sun illumination (solid lines) and in the dark (dotted lines) for the J-V test. Stability performances of CsPbBr3-xIx perovskite-sensitized solar cells where (d) corresponds to the Voc, (e) FF, (f) Jsc, and (g) PCE. For the stability test, the perovskite-sensitized solar cells were stored in the dark in a humidity-controlled desiccator after the 1 sun illumination test for 168 h. The complete set of perovskite solar cells used for both measurements is composed of ITO/c-TiO2/m-TiO2/CsPbBr3-xIx/Spiro-OMeTAD and PEDOT:PSS as the counter electrode. A mask with an aperture of 0.25 cm2 was used during the measurements.

Figure 4. (a) Stability performance and (b) hysteresis index (HI) of CsPbBr2.9I0.1 perovskitesensitized solar cell under exposure to UV and moisture (>80% RH). The CsPbBr2.9I0.1 perovskite-sensitized solar cell could potentially be employed for photo-supercapacitor applications. The HI was calculated based on Equation S4.



Figure 5. (a) Cyclic voltammograms, (b) areal capacitance calculated from cyclic voltammetry, (c) galvanostatic charge discharge, (d) Nyquist plot, and (e) cyclic retention of PEDOT:PSS-assisted RZCo//PyR supercapacitor in swagelok. RZCo represents reduced graphene oxide/zinc oxide/cobalt oxide, while PyR represents the polypyrrole/reduced graphene oxide.


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Figure 6. (a) Photovoltage response and (b) photocurrent response of CsPbBr2.9I0.1 perovskite-sensitized solar cell in presence of illumination and in dark condition. (c) Galvanostatic charge/discharge of integrated asymmetrical supercapacitor in dark condition.




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Cesium Lead Halide Inorganic-Based Perovskite-Sensitized Solar

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