Using an Open-Source Microcontroller and a Dye ... - ACS Publications

Laboratory Experiment Cite This: J. Chem. Educ. XXXX, XXX, XXX−XXX

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Using an Open-Source Microcontroller and a Dye-Sensitized Solar Cell To Guide Students from Basic Principles to a Practical Application P. Enciso, L. Luzuriaga, and S. Botasini* Laboratorio de Biomateriales, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Iguá 4225, 11400 Montevideo, Uruguay S Supporting Information *

ABSTRACT: This laboratory practice is intended for undergraduate students of chemistry, physics, biology, and engineering, to illustrate the simple concepts behind dye-sensitized solar cells (DSSCs), and how basic chemistry can be translated into a practical application through the use of microcontrollers. Unlike commercial counterparts, one of the main problems of handmade solar cells is their low efficiency that impedes their use as a power source, making the laboratory practice less appealing to students. In this work, we present a simple alternative application using an open-source microcontroller and a solar cell as a switch to turn the light on and off, depending on the actual lighting conditions in the room. KEYWORDS: Second-Year Undergraduate, Laboratory Instruction, Hands-On Learning/Manipulatives, Dyes/Pigments

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In this context, we propose a simple practice in which students can learn the chemistry behind the dye-sensitized solar cells, starting from the photosynthesis analogy,11 learning the use of semiconductors for the electron transfer, and ending up with a practical application that motivates the curiosity and the will to learn.12 Dye-sensitized solar cells (DSSCs) or Grätzel cells, in honor of the inventor,13−15 have attracted the attention of scientists and engineers, as reflected in the increased number of publications over the past few years.16 Compared to the silicon-based cells,17,18 DSSCs are less expensive and can be fabricated even with household materials,19 which makes them especially attractive for laboratory practices. The origin of these cells comes from photosynthesis biomimetics, where the components responsible for taking energy from the sun are natural pigments such as anthocyanins, chlorophylls, xanthophylls, flavones, and carotenes, contained in leaves, flowers, and fruits like raspberries, blackberries, ceibo’s flower, etc.20−22 The mechanism that makes DSSCs able to capture and transform light into electric energy relies on the electron flow among the dye, the titanium dioxide (semiconductor), the working electrode, the electrolyte, and the platinum or graphite counter electrode. In the dye, electrons are photoexcited to a higher energy state, allowing them to be transferred into the conduction band of the titanium oxide, and then to the electrode. The iodide/triiodide electrolyte restores the

t is hard to ignore the importance of electronics and programming in today’s chemistry.1 However, these disciplines are often absent or barely included in chemistry courses, probably because, not so long ago, creating computer applications or programming microcontrollers required some degree of specialization. Today, with the increasing availability of open-source microcontrollers, simplified programming languages, and abundant tutorials and manuals, the use of these kinds of technologies has become more popular.2,3 Microcontrollers are compact integrated circuits (like “small computers”), designed to control a specific operation, receive inputs from a variety of sensors, and interact with actuators.3 They are very popular in automation processes in everyday life, but they can also be valuable in analytical chemistry. They can translate analog to digital signals; be used to build pH-meters, thermometers, and portable and miniaturized instruments; and operate devices such as pumps, valves, automated titration systems, etc.2−6 The new trend in chemistry education is to incorporate microcontrollers in the curricula, that makes experiments more attractive and motivates student curiosity.3−5,7 In a world where technology is growing by leaps and bounds, it is particularly difficult to be amazed by the old chemistry, where laboratory practices sometimes look very far from practical application. Although one could argue that science should not be judged by the value of its use, it is a common fact that students are more likely to prefer a practical knowledge approach.8,9 As professors, it is our job to update our strategies to the new findings and trends, teaching the fundamentals thoroughly, but, more than anything, encouraging students to study and learn by themselves.10 © XXXX American Chemical Society and Division of Chemical Education, Inc.

Received: February 9, 2018 Revised: April 17, 2018

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DOI: 10.1021/acs.jchemed.8b00094 J. Chem. Educ. XXXX, XXX, XXX−XXX

Journal of Chemical Education

Laboratory Experiment

remaining charge vacancy in the dye, and the electron completes its cycle through the counter electrode (Figure 1).23,19 The voltage obtained after illumination corresponds to

Figure 2. Representation of the basic structure of the most common dye (anthocyanin) with the bond between the molecule and the Ti(IV) of the TiO2 layer. Figure 1. General view of the solar energy absorption process, showing the electron flow across the cell. The sky blue circles represent the electrolyte inserted within the pigment and the titanium dioxide. This illustrates one of the main reasons for the drop in efficiency, besides the electron recombination between the oxidized dye and the electrons that flow through the TiO2 layer, and the TiO2 and the I3−.

current is not enough to be useful as a power supply. In this context, we introduce a simple alternative application using an open-source microcontroller and the solar cell to act as a switch to turn a lamp on and off depending on the room illumination, emulating the street lights that automatically illuminate at nightfall.

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the difference between the quasi-Fermi level of the titanium dioxide and the Nernst potential of the redox couple in the electrolyte.11,13,20,21,24,25 DSSCs show efficiency values between 1% and 2% with good stability using natural dyes.25−27 In addition, organic compounds and metal complexes have been synthesized and utilized as molecular sensitizers in DSSCs to improve the efficiency to values as high as 12% with ruthenium- and cobaltbased complexes.14,28 The low efficiency is due to several reasons: one of them is the electrolyte filtration into the titanium dioxide, which causes a small localized short circuit that affects the overall performance of the cells. Although TiO2 has a high dielectric constant that prevents the electrostatic shielding of the injected electrons, recombination can still occur before the reduction of the dye by the redox couple. This effect is greater in TiO2 nanoparticle films, where the injected electrons are captured in trap states17 resulting in energy loss.11 Moreover, a poor adherence between the TiO2 paste and the dye could also generate a high internal resistance. The chemical nature of the dye also affects the electron flow since not all are suitable for transferring their excited electrons to the TiO2. The chemical nature of the interface should also be taken into account, as only the monolayer in close contact to the TiO2 is active. The dye structure must have several surface active moieties, like O and OH groups that are capable of chelating the Ti(IV) on the TiO2 surface29−31 (Figure 2). Temperature could also affect performance since electrolytes are volatile.32 Finally, the existence of other parallel reactions, caused by water molecules that remain in the dye solution, could alter the potential of the redox couple I−/I3−.33−35 Some authors19,36,37 have already proposed very interesting lab practices using chemical and household ingredients. However, one of the main disadvantages of these handmade cells is their low power efficiency, and therefore, the generated

MATERIALS AND METHODS

Dye Extraction

The extraction technique easily adapts to almost any natural source of anthocyanins, such as raspberries, blackberries, hibiscus tea leaves, etc.20,36 In our case, we used ceibo’s flowers (Erythrina crista-galli). The dye was extracted by smashing 2 g of fresh flowers in a mortar with 10 mL of ethanol (95% v/v) at room temperature, and filtered through Whatman No. 1 paper. Addition of heptane to the filtrate in a 1:1 ratio (v/v) permitted the separation of ceibo’s dyes from chlorophylls, due to their different hydrophobicity.38,39 Hence, concentrated dyes in the ethanolic phase are concentrated by solvent evaporation under a gentle stream of nitrogen to half its volume. Alternatively, dyes could be further purified using a C18 disposable column (Bakerbond spe, octadecyl) and methanol−acetonitrile (30:70 v/v) as the elution solvent. This step improves the cell efficiency, but it is not mandatory.20 DSSC Assembly

Fluorine-doped tin oxide (FTO) was chosen as the inert conductive surface for the working electrode modification. FTO/TiO 2 electrodes (DYESOL, screen printed with DYESOL’s DSL 18NR-AO Active Opaque Titanium paste) and FTO/Pt (screen printed with DYESOL’s Pt Platinum Catalyst) were used as working and counter electrodes, respectively. As pretreatment, FTO/TiO2 electrode was activated at 500 °C for 1 h (this activity was conducted without the students). At the beginning of the project, the FTO/TiO2 electrode was immersed in the dye solution for at least 30 min. Then, the electrode was rinsed with ethanol to remove impurities, and dried slowly with a hairdryer. The dye-sensitized TiO2 photoelectrode and the FTO/Pt counterelectrode were clipped together to make a sandwich-type cell. Finally, 50 mM iodide/ tri-iodide solution in acetonitrile (Solaronix Iodolyte AN-50) B




Figure 3. Connections between the DSSC, the relay, the power supply, the light bulb, and the Arduino Uno module (a). Relay connection to the outlet socket connected to the power supply (b), relay diagram (c), the DSSC (d), and the electrical diagram (e). The microcontroller monitors the level of illumination in the room by detecting the voltage produced by the solar cell and, through the relay, opens or closes the circuit between the power supply and the light bulb.

was injected into the space between the electrodes with the aid of a syringe. Arduino Connections

The pin 5 and ground (GND) from the Arduino UNO board were connected to pins A and B in the 5 V relay (QIANJI, JQC-3F(T73)), while COM/pole and Normally Open (NO) relay pins were connected in serial to the electric power supply. It is important to highlight that most Arduino boards do not require a resistance between the relay and the 5 V source; however, a 1 kΩ resistance could be added in series as a precaution (not in our case). The relay’s connections were welded and insulated with a plugging box as shown in Figure 3. Solar cells were connected to the Arduino board pin A0 and ground, respectively. The software needed to run the Arduino is quite basic (viz. Supporting Information); therefore, IT skills are not required to understand the code. Although the Arduino module could be replaced with a couple of transistors (which are less expensive), the use of a microcontroller is a better option since signal threshold can be easily programmed to detect different light intensities and also provides the 5 V needed to trigger the relay.

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RESULTS AND DISCUSSION This practice was designed for small groups of students (ideally no more than 5 groups of 2 students each). The overall practice took about 4 h (all the necessary material was supplied in advance) including a 30 min introduction to the practice. This experiment was regularly conducted (10 times) as a complementary activity, although the evaluation test was carried out by a group of 11 volunteers to qualitatively assess the general perception of the practice. The class started with a demonstration of the final prototype that students had to replicate during the practice. The classroom light was turned off, and after 2 s it was restored by the DSSC/Ardunio device connected to a desk lamp. Then, the classroom light was turned on again, and the desk lamp turned off, to everyone’s amazement. The first part of the class (no more than 30 min) was dedicated to describing the components of the device and how light was harvested to produce the small voltage necessary to be measured by the Arduino module). Cell assemblage began with the extraction of the dye from the ceibo’s flowers. The students discussed the differences in the molecule structure between the dye and the chlorophyll, that makes the latter more soluble in heptane than in ethanol. Once the DSSC was assembled, the students measured the voltage and the current in the presence and absence of light. They learned the difference between voltage and current where the former was the only measurable property (ca. 0.2 V with light exposure for the ceibo’s flower), while the latter was too small to be detected, due to the high cell internal resistance (ca. 1 MΩ). A key parameter in the device is the switching threshold. Therefore, it is important to measure the voltage drop vs time. This was carried out with a voltammeter and with the Arduino monitor, in order to correlate the “real” voltage with the

Cell Time Response

First, the light was turned on until a constant voltage was measured. Then, the light was turned off, and the cell potential was measured at 20 s intervals using a conventional voltammeter and the Arduino microcontroller. It is important to have the Arduino IDE monitor window opened in order to display the output data.

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HAZARDS AND SAFETY PRECAUTIONS

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TEACHING AND LEARNING OUTCOMES

• comprehend the principles behind a DSSC solar cell, highlighting the importance of biomimetic technologies (in this case the photosynthesis) • recognize how these theoretical ideas can be translated into practice, by assembling a solar cell and measuring its voltage output • apply the technology to a practical application using the cell as a light sensor • acquire experience in the use of open-source microcontrollers, for experimental automation

By no means should laboratory practices be carried out without supervision. In addition, although the used chemical reagents are harmless, gloves, glasses, and protective clothing should be used at all times during the cell assemblage. Gloves must be removed for welding. It is also important to use an exhaust fan or an extraction hood to avoid fumes.

By the end of this practice, students will be able to C




numerical value displayed by the microcontroller. Arduino boards contain a 10 bit analog to digital converter that can map input voltages between 0 and 5 V into integer values between 0 and 1023.40 The equivalence is defined by the formula m Vout = × 5V (1) 1024

out that “the practice was very good and original; as simple natural resources can be used to obtain energy”. In general, the students were excited and eager to learn more about the solar cell technology during and even after class. We carried out a satisfaction survey, revealing positive results and good acceptance (Table 1).

where Vout represents the measured voltage and m is the number displayed by the Arduino monitor (m = sensor in the program code). Although eq 1 can be easily added to the program code, we believe it is important to show the calculation separately to better illustrate how the microcontroller works, and to visualize the correlation between the microcontroller output and the measured voltage. This also trains students on how to take measurements by hand and how to be systematic. The time response curve (Figure 4) help the students to discuss and

Table 1. Comparative Survey Results Average Scorea (N = 11)

Survey Prompts for Student Response The topic was interesting. I have previous experience in building solar cells or programming. The activity met my expectations. The depth of the covered topics was satisfactory. The duration of the practice was adequate. The contents were been clearly shown. I think the activity was useful for my career. I would recommend this activity to other students. The activity was difficult. The activity was original. I have learned from this activity. I would like to continue exploring these topics in the future.

4.3 1.5 4.0 4.0 4.5 4.5 4.3 4.3 2.3 4.4 4.7 3.9

a The scale for these scores has a range of 1−5, with 5 being “totally agree”, and 1 being “totally disagree”.

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CONCLUSIONS We presented an original laboratory activity that exemplifies the combination of different disciplines and concepts, from chemistry, physics, biology, and engineering, in a way that motivates the students’ curiosity and ingenuity. Furthermore, we introduced the use of microcontrollers, often absent in chemistry courses, which we believe are very important in today’s chemistry where miniaturized and portable sensor devices are more common. In addition, we provided a basic knowledge of one of the most promising technologies in the field of renewable energies. Regarding the learning outcomes, students effectively learned about the basic science of solar cell technology, microcontrollers, and their use. Moreover, this activity highlights the importance of biomimesis, and interdisciplinary thinking in today’s applications.

Figure 4. Potential drop vs time. The graph shows a perfect correlation between the measurements obtained by hand (■) and by the microcontroller (---). The numeric data obtained by the microcontroller were converted to electric potential by eq 1.

decide which value should be used as a threshold to sense the amount of illumination, balancing the response time of the sensor, and the light intensity (voltage) which can be considered as insufficient for lighting purposes. It is worth noting that the response curve and the threshold value were different for each group depending on how they assembled the solar cell and how much pigment was effectively adsorbed to the electrode. In addition, we asked them to calculate the time they should wait to get the sensor response. These steps highlight the importance of performing a basic calibration analysis before going into the application. We explained the concept of a relay, how the microcontroller activates the switch, and how the welding is performed. In this part, they learned to weld and properly isolate the connections between the cables and the relay. Professors supervised all connections before allowing the students to plug in the lamps. Finally, each group ran the Arduino program. Once everything was completed, the lamps in the classrooms were turned off, and after a couple of seconds the classroom lit up again with the students’ devices. This activity was carried out with second-year biochemistry students to illustrate how natural dyes could be used to create a solar cell, and how basic science can be translated into a practical and useful application. One of the students pointed

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available on the ACS Publications website at DOI: 10.1021/acs.jchemed.8b00094. Complete description of the solar cell and microcontroller code (PDF, DOCX)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

S. Botasini: 0000-0002-6488-5886 Notes

The authors declare no competing financial interest. D



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(20) Enciso, P.; Cerdá, M. F. Solar Cells Based on the Use of Photosensitizers Obtained from Antarctic Red Algae. Cold Reg. Sci. Technol. 2016, 126, 51−54. (21) Wang, L.; Shi, Y.; Bai, X.; Xing, Y.; Zhang, H.; Wang, L.; Guo, W.; Wang, N.; Ma, T.; Grätzel, M. From Marine Plants to Photovoltaic Devices. Energy Environ. Sci. 2014, 7 (1), 343−346. (22) Hao, S.; Wu, J.; Huang, Y.; Lin, J. Natural Dyes as Photosensitizers for Dye-Sensitized Solar Cell. Sol. Energy 2006, 80 (2), 209−216. (23) Kumara, N. T. R. N.; Lim, A.; Lim, C. M.; Petra, M. I.; Ekanayake, P. Recent Progress and Utilization of Natural Pigments in Dye Sensitized Solar Cells: A Review. Renewable Sustainable Energy Rev. 2017, 78, 301−317. (24) Grätzel, M. Conversion of Sunlight to Electric Power by Nanocrystalline Dye-Sensitized Solar Cells. J. Photochem. Photobiol., A 2004, 164 (1−3), 3−14. (25) Richhariya, G.; Kumar, A.; Tekasakul, P.; Gupta, B. Natural Dyes for Dye Sensitized Solar Cell_ A Review. Renewable Sustainable Energy Rev. 2017, 69, 705−718. (26) Calogero, G.; Bartolotta, A.; Di Marco, G.; Di Carlo, A.; Bonaccorso, F. Vegetable-Based Dye-Sensitized Solar Cells. Chem. Soc. Rev. 2015, 44 (10), 3244−3294. (27) Shalini, S.; Balasundara prabhu, R.; Prasanna, S.; Mallick, T. K.; Senthilarasu, S. Review on Natural Dye Sensitized Solar Cells: Operation, Materials and Methods. Renewable Sustainable Energy Rev. 2015, 51, 1306−1325. (28) Yella, A.; Lee, H.-W.; Tsao, H. N.; Yi, C.; Chandiran, A. K.; Nazeeruddin, M. K.; Diau, E. W.-G.; Yeh, C.-Y.; Zakeeruddin, S. M.; Gratzel, M. Porphyrin-Sensitized Solar Cells with Cobalt (II/III)Based Redox Electrolyte Exceed 12% Efficiency. Science 2011, 334 (6056), 629−634. (29) Smestad, G. P.; Gratzel, M. Demonstrating Electron Transfer and Nanotechnology: A Natural Dye-Sensitized Nanocrystalline Energy Converter. J. Chem. Educ. 1998, 75 (6), 752. (30) Tennakone, K.; Kumarasinghe, A. R.; Kumara, G. R. R. A.; Wijayantha, K. G. U.; Sirimanne, P. M. Nanoporous TiO2 Photoanode Sensitized with the Flower Pigment Cyanidin. J. Photochem. Photobiol., A 1997, 108 (2−3), 193−195. (31) Alhamed, M.; Issa, A.; Doubal, A. Studying of Natural Dyes Properties as Photo-Sensitizer for Dye Sensitized Solar Cells (DSSC). J. Electron Devices 2012, 16, 1370−1383. (32) Mehmood, U.; Al-Ahmed, A.; Al-Sulaiman, F. A.; Malik, M. I.; Shehzad, F.; Khan, A. U. H. Effect of Temperature on the Photovoltaic Performance and Stability of Solid-State Dye-Sensitized Solar Cells: A Review. Renewable Sustainable Energy Rev. 2017, 79, 946−959. (33) Chu, L.; Qin, Z.; Liu, W.; Ma, X. Inhibition of Charge Recombination for Enhanced Dye-Sensitized Solar Cells and SelfPowered UV Sensors by Surface Modification. Appl. Surf. Sci. 2016, 389, 802−809. (34) Prima, E. C.; Hidayat, N. N.; Yuliarto, B.; Suyatman; Dipojono, H. K. A Combined Spectroscopic and TDDFT Study of Natural Dyes Extracted from Fruit Peels of Citrus Reticulata and Musa Acuminata for Dye-Sensitized Solar Cells. Spectrochim. Acta, Part A 2017, 171, 112−125. (35) Narayan, M. R. Dye Sensitized Solar Cells Based on Natural Photosensitizers. Renewable Sustainable Energy Rev. 2012, 16 (1), 208− 215. (36) Smestad, G. P. Education and Solar Conversion: Demostrating Electron Transfer. Sol. Energy Mater. Sol. Cells 1998, 55 (1−2), 157− 178. (37) Enlow, J. L.; Marin, D. M.; Walter, M. G. Developing a Polymer Semiconductor Education Kit and Curriculum for High School Science Classrooms. Macromol. Symp. 2015, 355 (1), 43−51. (38) Rodriguez-Saona, L. E.; Wrolstad, R. E. Extraction, Isolation, and Purification of. Curr. Protoc. Food Anal. Chem. 2001, F1.1.1− F1.1.11. (39) Cerda, M.; Enciso, P. Caracterización de Las Antocianinas de La Flor de Ceibo Como Sensibilizadores Naturales Para Su Uso En Celdas Fotovoltaicas. Rev. del Lab. tecnológico Uruguay 2014, 9, 91−97.

ACKNOWLEDGMENTS This work would not have been possible without the contribution of Dr. Michael Grätzel and his collaborators who kindly opened the door of their lab and shared their knowledge and experience. We also want to thank Dr. Eduardo Méndez and Dr. Fernanda Cerdá for their support. Finally, we would like to acknowledge the agencies CSIC, ANII, and PEDECIBA for their financial support.

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REFERENCES

(1) Abola, E.; Kuhn, P.; Earnest, T.; Stevens, R. C. Automation of XRay Crystallography. Nat. Struct. Biol. 2000, 7, 973−977. (2) Papadopoulos, N. J.; Jannakoudakis, A. A Chemical Instrumentation Course on Microcontrollers and Op Amps. Construction of a pH Meter. J. Chem. Educ. 2016, 93 (7), 1323−1325. (3) Urban, P. L. Open-Source Electronics as a Technological Aid in Chemical Education. J. Chem. Educ. 2014, 91 (5), 751−752. (4) Walkowiak, M.; Nehring, A. Using ChemDuino, Excel, and PowerPoint as Tools for Real-Time Measurement Representation in Class. J. Chem. Educ. 2016, 93 (4), 778−780. (5) Mabbott, G. A. Teaching Electronics and Laboratory Automation Using Microcontroller Boards. J. Chem. Educ. 2014, 91 (9), 1458− 1463. (6) Pearce, J. M. Building Research Equipment with Free, OpenSource Hardware. Science 2012, 337 (6100), 1303−1304. (7) Kubínová, Š.; Šlégr, J. ChemDuino: Adapting Arduino for LowCost Chemical Measurements in Lecture and Laboratory. J. Chem. Educ. 2015, 92 (10), 1751−1753. (8) Mortazavi, A.; Williams, B. A.; McCue, K.; Schaeffer, L.; Wold, B. Mapping and Quantifying Mammalian Transcriptomes by RNA-Seq. Nat. Methods 2008, 5 (7), 621−628. (9) Kolb, A. Y.; Kolb, D. a. Learning Styles and Learning Spaces: Enhancing Experiential Learning in Higher Education. Acad. Manag. Learn. Educ. 2005, 4 (2), 193−212. (10) Brouwer, N.; Byers, B.; Mcdonnell, C. Report from ECTN Working Group Developing Independent Learners in Chemistry; European Chemistry Thematic Network Association: Ulster, U.K., 2006. (11) Prabavathy, N.; Shalini, S.; Balasundaraprabhu, R.; Velauthapillai, D.; Prasanna, S.; Muthukumarasamy, N. Enhancement in the Photostability of Natural Dyes for Dye-Sensitized Solar Cell (DSSC) Applications: A Review. Int. J. Energy Res. 2017, 41 (10), 1372−1396. (12) Cummings, S. D. ConfChem Conference on Educating the next Generation: Green and Sustainable Chemistry - Solar Energy: A Chemistry Course on Sustainability for General Science Education and Quantitative Reasoning. J. Chem. Educ. 2013, 90 (4), 523−524. (13) Grätzel, M.; O'Regan, B. A Low-Cost, High-Efficiency Solar Cell Based on Dye-Sensitized Colloidal TiO2 Films. Nature 1991, 353, 737−740. (14) Wang, P.; Zakeeruddin, S. M.; Moser, J. E.; Nazeeruddin, M. K.; Sekiguchi, T.; Grätzel, M. A Stable Quasi-Solid-State Dye-Sensitized Solar Cell with an Amphiphilic Ruthenium Sensitizer and Polymer Gel Electrolyte. Nat. Mater. 2003, 2 (6), 402−407. (15) Grätzel, M. Dye-Sensitized Solar Cells. J. Photochem. Photobiol., C 2003, 4 (2), 145−153. (16) Gong, J.; Sumathy, K.; Qiao, Q.; Zhou, Z. Review on DyeSensitized Solar Cells (DSSCs): Advanced Techniques and Research Trends. Renewable Sustainable Energy Rev. 2017, 68, 234−246. (17) Mori, S.; Yanagida, S. TiO2 -Based Dye-Sensitized Solar Cell. In Nanostructured Materials for Solar Energy Conversion, 1st ed.; Elsevier: Amsterdam, 2006; pp 193−225. (18) Aberle, A. G. Surface Passivation of Crystalline Silicon Solar Cells: A Review. Prog. Photovoltaics 2000, 8 (5), 473−487. (19) Smith, Y. R.; Crone, E.; Subramanian, V. A Simple Photocell to Demonstrate Solar Energy Using Benign Household Ingredients. J. Chem. Educ. 2013, 90 (10), 1358−1361. E




(40) Arduino. Arduino Manual: analogRead(). https://www.arduino. cc/en/Reference/AnalogRead (accessed Apr 2018).

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