Page 182 - CW E-Magazine (22-10-2024)

Special Report Special Report

OPVs are currently only about half Table 2: Chemicals and gases used in electronics manufacturing solar cells has signifi cantly improved,
as effi cient as crystalline silicon cells Category Products with lab-scale cells now exceeding
and have shorter operating lifetimes, Bulk gases Nitrogen, oxygen, argon, helium, and hydrogen; effi ciencies of 26%, up from about 20%
but could be less expensive to manu- a decade ago.
facture in high volumes. They can also Dopants gases Arsine, phosphine, boron trichloride, boron tri-
be applied to a variety of supporting fl uoride, and diborane; The record lab cell effi ciency is
materials, such as fl exible plastic, mak- Etchant gases Boron trichloride, chlorine, chlorine trifl uoride, 27.3% for mono-crystalline and 24.4%
ing OPV able to serve a wide variety hydrogen chloride, hydrogen fl uoride, nitrogen for multi-crystalline silicon wafer-
of uses. trifl uoride, silicon tetrafl uoride, sulfur hexa- based technology. The highest lab
fl uoride, tetra-fl uoromethane, trifl uoromethane, effi ciency in TFT is 23.4% for CIGS and
Other chemical usage difluoromethane, fluoromethane, hexafluoro- 21.0% for Cd-Te solar cells. Record lab
Other chemicals used in PVs ethane, pentafl uoroethane, octafl uoropropane, cell effi ciency for Perovskite is 25.2%.
include: and octafl uorocyclobutane;
 Conductive inks, based on silver Chemical vapour deposition Silane, dichlorosilane, trichlorosilane, silicon tetra- In the last 10 years, the effi ciency
Fig. 3: Market share of Thin Film Technologies by type. and copper, which are used for (CVD) chemicals chloride, disilane, tetraethylorthosilicate, silicon of commercial mono-crystalline wafer-
Source: Reference 2.
making the electrical contacts that tetrafl uoride, methylsilane, germane, ammonia, based silicon modules increased from
of materials that are printed, coated, or methylammonium lead iodide. Solvents, collect and transport the generated nitrous oxide, and tungsten hexafl uoride; and about 16% to 22% and more. At the
vacuum-deposited onto an underlying such as dimethylformamide and electricity; Other wet chemicals Acetic acid, acetone, ammonium fluoride, same time, the effi ciency of Cd-Te
support layer (substrate). They are typi- dimethyl sulphoxide are critical in the  Encapsulants, of which ethylene- ammonium hydroxide, hydrochloric acid, hydro module increased from 9% to nearly

cally easy to assemble and can reach formation of the perovskite layer dur- vinyl acetate (EVA) copolymer is fl uoric acid, hydrogen peroxide, isopropyl alcohol, 20%.
effi ciencies similar to crystalline silicon. ing the fabrication process. most commonly used, to protect nitric acid, phosphoric acid, and sulfuric acid.
In the lab, perovskite solar cell effi - the PV cells from moisture and In the laboratory, the best perform-
ciencies have improved faster than any Organic photovoltaics mechanical damage; and Table 3: Chemicals used in crystalline silicon technology ing modules are based on mono-crys-
other PV material, from 3% in 2009 to Organic PVs (OPVs) are made  Back-sheet materials that includes Type Materials & chemicals talline silicon with 24.9% effi ciency.

over 25% in 2020. To be commercially from conjugated polymers (e.g., poly polyvinylidene fl uoride (PVDF), Basic materials Monocrystalline silicon, polycrystalline silicon. Record effi ciencies demonstrate the
viable, perovskite PV cells have to (3-hexylthiophene) (P3HT)), which are used to protect the back of solar Speciality gases Ammonia, argon, fl uorine, nitrogen trifl uoride, nitrous oxide. potential for further effi ciency increases
become stable enough to survive 20 years used as the active layer in OPV cells. panels. Bulk gases Hydrogen, nitrogen, oxygen. at the production level.
outdoors, so researchers are working on Fullerenes (e.g., PCBM, ([6,6]-phenyl-C -
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making them more durable and deve- butyric acid methyl ester)) are often Chemicals are also used in the qua- Silicon precursor Dichlorosilane, silane, silicon tetrachloride, trichlorosilane. Perovskite solar cells have been a
loping large-scale, low-cost manufac- used as electron acceptors in OPV cells, lity control and testing stages of PV manu- gases major breakthrough in the last decade,
turing techniques. and alternatives such as diketopyrro- facturing. Solutions and reagents are Dopants Boron tribromide, phosphorus oxychloride. and rapidly advanced in terms of effi -
lopyrrole (DPP) and non-fullerene employed to test for impurities, check Wet chemicals Acetic acid, ammonium hydroxide, ethanol, ethylene, ciencies from around 10% to over 25%.
Perovskite solar cells commonly acceptors have gained popularity in electrical characteristics, and ensure hydrochloric acid, hydrofl uoric acid, hydrogen peroxide, They are also being integrated into
use lead halide perovskites, such recent years. solar cells meet performance standards. isopropyl alcohol, nitric acid, phosphoric acid, polyethy- tandem cells with silicon, pushing the
lene glycol, potassium hydroxide, sodium hydroxide, combined effi ciencies beyond 30%.
sulphuric acid, tertrafl uoroethylene.
Metallisation Front side n-type (silver); back side p-type aluminium. For concentrated PVs (CPVs),
Encapsulants Ethylene vinyl acetate. multi-junction cells have reached
effi ciencies of over 40% in lab settings,
After manufacturing, PV modules are rials like silicon, silver, and rare metals, benefi ting from advances in material
installed in various applications, ranging and the safe disposal of hazardous sub- science and fabrication techniques.
from residential rooftops to large-scale stances. The development of chemical CPVs works with lenses that concen-
solar farms. The chemical industry’s in- processes to recycle and repurpose PV trate the sunlight onto a relatively small
volvement extends to providing materials materials is crucial for sustainability area. This happens in combination with
like sealants, adhesives, and coatings that and reducing the environmental impact primary and secondary lenses. These
protect the installations from environmen- of solar energy. are used directly on the solar cell, which
tal degradation, UV exposure, and mecha- turns the sunlight into electrical energy.
nical stress. As PV systems reach the end of PV innovations – focus areas The primary lenses that are connected
their operational life, the chemical industry in front of the solar cells focus the light
contributes to the recycling process. This Effi ciency improvements and channel it through secondary lenses
Fig. 4: Materials used in a typical silicon PV cell. includes the recovery of valuable mate- The effi ciency of silicon-based that are attached directly to the cell.

182 Chemical Weekly October 22, 2024 Chemical Weekly October 22, 2024 183

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