WASHABLE SOLAR CELL IN SELF-POWERED TEXTILES FOR WEARABLE ELECTRONICS
BTech. Solar and alternate energy
ETTP100: Term Paper
Mr. Jerrin Varghese
Due to the growth of human civilization, there has been a large demand for energy. Energy production by burning of fossil fuels is how it is happening around the world. This causes various environmental issues including the depletion of ozone layer and global warming. Therefore, energy harvesting from renewable sources have become an urgent issue for the present generation and the upcoming ones. Among all the renewable sources, solar energy is the most effiecient and promising candidate due to the vast availability and hight radiation energy. They produce only a few by-products. It requires no extra fuel supply even.
Organic-inorganic hybrid halide perovskite materials have attracted attention as they possess opto-physical properties but also have facile solution processability. Due to these reasons, PVSCs are considered the most effiecient transformative photovoltaic technology. The current power conversion efficiency of this perocskite solar cell has reached over 22%.
PCE of PVSC can rival the performance of traditional inorganic photovoltaic techniques. These perocskite materials are said to be susceptible to moisture, heat, and intense light/illumination. The encapsulation of of PVSC will play a game changing role to sustain its long-term stability for real operations.
WHAT IS A SOLAR CELL?
Nowadays, solar cells can be found almost everywhere, from your home to the space. They are also known as photovoltaic cells or PV cells. These cells harvest electricity directly from the visible light by the means of photovoltaic effect. When many photovoltaic cells are connected together, they are known as solar panels or modules.
PV cells are made of semiconductors. The commonly used semiconductor for the production of these cell is silicon(Si). When the light falls on the cell’s surface, a part of it is absorbed within the semiconductor material. The absorbed light’s energy is then transferred to the semiconductor which results in the electrons being loose allowing them to move easily or freely.
Photovoltaic cells got electric fields which forces the electron (free) to flow in a certain direction. When the top and bottom of the pv cells areplaced with metal contacts, drawing of current is possible for external uses.
WHAT IS A WASHABLE SOLAR CELL?
Wearing hard and flat solar panel is the last thing people want to wear. Portable electronic devices can be powered by the integration of flexible solar cells onto clothing. Although PVs suffers from the limitations of ambient light intensity, it is considered to be the most advanced and efficient way for producing electricity.
Nowadays, Portable devices require only a very low energy. This gives us the advantage of integrating solar cells onto clothing. Various sensors can be attached to these clothing such as a heart rate sensor. The efficiency of these solar cells decreased only by 5.5% per cent when soaked in water for 2 hours.
TYPES OF PVSCs
By and large, PVSCs can be separated into two kinds, n-I-p and p-i-n structures, as indicated by the grouping of the utilized charge transporting layers (CTLs). The prototypical PVSC depends on a regular n-I-p arrangement as developed from the mesoporous dye-sensitized solar cells (DSSCs), which comprises of a transition metal oxide (TMO) scaffold as an electron transporting layer (ETL) at gadget’s base side. Notwithstanding, such complex procedures would subtly increment the creation expenses and point of confinement the substrate decision.
Further, it obstructs the across the board utilizations of the determined gadgets in the adaptable and wearable hardware, for which polymeric substrates with low glass change temperatures were normally utilized. Hence, flexible low temperature techniques are created for TiOx.
As of late, we have utilized a low-temperature electro-deposited SnO2 film to fill in as an effective ETL to understand a proficient PVSC on standard unbending ITO substrate. With respect to low-temperature producing process, we ceaselessly investigated its viability in manufacturing effective adaptable PVSCs. An ITO/polyethylene naphthalate (PEN) substrate was chosen to compare with the regular inflexible ITO/glass substrate. It has been recognized that the ITO/flexible substrates based devices normally have inferior performance as compared with the unbending ITO/glass counterparts because of the weak and unsuitable bendable nature of ITO.
We first surprisingly watched that the nature of the electro-deposited SnO2 on the ITO/PEN substrate is much worse than the film kept on the regular ITO/glass substrate. To address this lack, we in this manner presented an extra PCBM layer onto the stored SnO2 layer. The fullerene materials have not exclusively been exhibited as proficient ETLs for PVSCs,but additionally been demonstrated as adequate surface modifiers of TMO-based ETLs to facilitate the charge exchange and transport amongst them and perovskite in the customary n-I-p PVSCs.Afer including this layer onto the pre-electrodeposited SnO2 layer,the initially unpleasant surface was somewhat leveled and the perfect sharp edges of discrete SnO2 spaces was smoothened, showing that PCBM layer secured the whole surface to evade any immediate contact amongst perovskite and ITO electrode.
Over the morphological issue, high translucency is another critical thing for a qualified ETL for accomplishing high effectiveness since it can keep the parasitical absorption of perovskite absorber prevented. The bi layered ETL can even now have a sensible transmittance of ~80% in the scope of wavelengths greater than 600 nm regardless of the somewhat diminished transmittance beneath 600 nm because of the assimilation of the PCBM layer.
Keeping in mind the end goal to build up a stable adaptable PVSC, we topped the finished device with a malleable elastomer. A thin glass cover slip is the most used encapsulation system to date. Its unbending nature however obstructs the further applications on adaptable hardware. Henceforth, the flexible elastomer was picked as the epitomizing material because of its easy accessibility, not too bad attachment, and great obstruction for outside substances.Encouragingly, both encapsulating materials can yield comparative execution, qualifying the commercial elastomer as an attainable encapsulation material. Given the great adhesive property of the elastomer, it may not exclusively can fill in as a praiseworthy encapsulation material for adaptable PVSCs yet additionally can facilitate the manufacture of textile based PVSCs.
Prominently, we likewise manufactured the devices on the consistent ITO/ glass substrate for a reasonable examination. Diverse to the instance of utilizing adaptable substrate, there is just slight difference between the SnO2-based device and SnO2/PCBM-based device. The two devices displayed hysteresis-free J– V qualities also, yields PCEs of ~14%. This proposes that very well developed SnO2 of great quality can be effectively accomplished on the ITO/glass substrate through electro-deposition and the extra PCBM inter layer hence assumes a less critical role.
HOW IT IS IMPLEMENTED ONTO FABRIC
a-Si:H cells were put onto woven texture, not by holding or laminating convectional crystalline cells as is usually done, however rather by directly applying the cell layers on to the texture itself. By utilizing PECVD(Plasma-enhanced chemical vapor deposition) we can use polyester, maybe the most broad polymer texture, as it is steady to over the deposition temperature of a-Si:H and isn’t influenced by the plasma itself. The cell is a multi-layer device in light of making the texture electrically conducting while keeping up its conductivity when flexed.
Over this we include the three P-I-N a-Si:H layers by PECVD and finish the fundamental cell by a sputtered translucent oxide layer, at present of indium tin oxide (ITO) however in future this could be aluminum doped zinc oxide (AZO). At long last the cells are encapsulated in a polymer covering by one of a few elective strategies, as per the end use and required life expectancy.
Another preferred standpoint of framing cells specifically on a fabric is the option for incorporating connections between cells. Individual solar cells produce around one volt thus should be associated in a series arrangement to build the yield voltage to a more helpful esteem. With conventional crystalline cells, this is accomplished by bonding metal strips between cells mounted in a supporting casing. With thin film cells there might be the choice for interconnecting them as a feature of the fabrication procedure, on a substrate that accompanies several cells. With flexible cells on fabrics we can do much a similar incorporating of cell associations with evaporated metal forming the contacts between the top point of one cell and the base of the neighboring one. The yield current from a cell relies upon its area so in an series arrangement of cells, everyone must have a similar region in spite of the fact that they might be of distinct shapes as per the artistic designs.
The solar cell initially had an energy effectiveness of 7.9%, creating a current of 7.86 milliwatts for each square centimeter. The material was then soaked in water continuously for 2 hours. it was then observed that the productivity had diminished by just 5.4%. The material was subjected to pressure in water, and after 20 cycles, regardless it had 80% of its original efficiency. Under 0.8 sun enlightenment, the control device utilizing simplex electro-deposited SnO2 ETL yielded a low photocurrent alongside a poor fill factor (FF), which can be followed to the high series resistance(Rs) and low shunt resistance(Rsh) caused due to the SnO2 layer’s low-quality . Its discontinuous morphology related with separated island-like areas blocks effective charge transport and conceive serious accusation recombination. By presenting a thin PCBM layer, the resultant performance can be fundamentally moved forward.
The difficulties of making fruitful sun based cells on a texture are currently being met. The first was to render a woven texture electrically conducting over selected areas prior to trying deposition of silicon. A double layer beats any inclination for minor breaks in a single conductor to reach out over the twist or weft of the texture. Later on, if adequately high voltages and streams can be acknowledged, solar cells in garments could likewise be utilized to recharge cell phones and may even have the capacity to supply household power, which means things like OPV awnings could be utilized as a part of, for instance, developing regions.
The two primary obstacles that should be overcome are the cost and size of the solar cells. The cells are at present constrained to 10 centimeters by 10 centimeters and are genuinely costly to create. However, this is for the most part down to the cost of the active layer.
Right now, OPV models can’t go up against conventional inorganic solar cells for life span and consequently cost. rooftop models target lifetimes of 20 years, while organic photovoltaic cells are targeting lifetimes of under 10 years for glass-based items and under five years for flexible items.
In the event that the solar cells could be joined with thin, lightweight batteries, their value could be upgraded much further. If the batteries could have been made very thin and flexible, energy storage would have been easier.
Recharge cell phones.
Makes it possible to attach sensors.
It can be used for Charging GoPro camera’s under water.
Run low voltage devices or gadgets.
Used as shades for cars.
For the working of swimming pool lights.
Useful for long drives and camping.
Organic– inorganic mixture perovskite solar cells (PVSC) have showed up as promising high power-per-weight control frameworks for wearable electronic gadgets. In this, we used a low-temperature electro-deposited tin oxide (SnO2) electron-transporting layer (ETL) combined with a thin PCBM ETL and a fuctional encapsulating layer to understand a proficient, stable fabric-based adaptable PVSC. We initially exhibited that an effortlessly accessible elastomer can fill in as a effective encapsulating material for the fabricated flexible PVSC, as exemplified by thewell developed stability and waterproof properties. Besides, we set up that the great adhesive properties created by the elastomer can generally improve the deployable capacity of the finished device stack as proofed by the easy integration of a finished gadget stack onto a fabric. Therefore, a ?15% fabric based flexible PVSC with enhanced encompassing strength and launderable capacity was illustrated. A proof-of-concept device was effectively integrated with other electronic devices on a unitary material to provide a proficient power supply framework for wearable electronic gadgets. The discoveries uncovered in this work can advance the future potential uses of PVSCs in wearable gadget applications.
12.Lipomi, D. J., Tee, B. C. K., Vosgueritchian, M. & Bao, Z. Stretchable organic solar cells. Adv. Mater. 23, 1771–1775 (2011).
13.Kaltenbrunner, M. et al. Ultrathin and lightweight organic solar cells with high flexibility. Nat. Commun. 3, 770 (2012).
14.Dennler, G., Lungenschmied, C., Neugebauer, H., Sariciftci, N. S. & Labouret, A. Flexible, conjugated polymer-fullerene-based bulk-heterojunction solar cells: Basics, encapsulation, and integration. J. Mater. Res. 20, 3224–3233 (2005).
15.Kim, D.-H. et al. Stretchable and foldable silicon integrated circuits. Science 320, 507–511 (2008).
16.National Renewable Energy Laboratory (NREL), Research cell record efficiency chart. https://www.nrel.gov/pv/assets/images/efficiency-chart.png, July 2017.