A Review On The Exploration Of The Red Phosphors For The Fabrication Of Phosphor-Converted-LEDs For Plant Growth In Indoor Farming

Abstract

The World Population Prospects 2019: Highlights, published by the Population Division of the UN Department of Economic and Social Affairs, reports that the world population could reach its peak around the end of the current century, at a level of nearly 11 billion. This increase will need to be accompanied by increases in food production, and that too in a world where arable land is becoming an increasingly scarce resource. To address this problem, a relatively new agricultural practice known as Vertical Indoor Farming (VIF), which relies on height, rather than width, to generate agricultural production has emerged as a form of ‘sustainable cultivation of plants.’ It is important to mention that chlorophyll a and chlorophyll b absorb red light ranging from 600 nm to 700 nm wavelength. Red emission from AlGaInP red LED chip is comprised of rather narrow emission spectra from 625 nm–640 nm. In this review, we elucidate a series of transition metal (Cr3+/Mn4+)/ rare-earth (Eu2+) doped silicate and aluminate phosphors emitting in the red region (600 nm – 700 nm) exhibiting high luminescence efficiency for the fabrication of phosphor-converted red LED, which can be mounted on blue LED chip. Consequently the red LED, which will be fabricated by using these red emitting phosphors mounted on blue LED chip will provide the red light in 600 nm to 700 nm region, which can be absorbed by chlorophyll a and chlorophyll b. Solution synthesis mediated approaches will be discussed for the synthesis of these high efficiency phosphors.

Luminescence Performance of Mn4+ Activated BaLa2Al2O7 Phosphors

“…4 So far, lots of phosphors have been synthesized and investigated to explore their potential applications in various pc-LEDs. [5][6][7][8] As a general rule, a phosphor is constituted by a host and one or more doping ions. The hosts can be inorganic or organic materials.…”

“…Among transition metal ions, Mn 4+ ion is took notice on account of its efficient and sharp red emission within 600-750 nm corresponding to the spinforbidden 2 E g → 4 A 2g transition when it locates in an octahedral site. 8 Meanwhile, it exists two broad absorbance bands in UV-blue light region resulting from the spin-allowed 4 A 2g → 4 T 2g and 4 A 2g → 4 T 1g ( 4 F) transitions, meaning that Mn 4+ doped phosphors are suitable for pc-LEDs pumped with NUV/UV/blue LEDs. In recent years, some Mn 4+ doped phosphors have been synthesized and researched, such as Mn 4+ doped fluoride phosphors, 4,9 Mn 4+ doped double perovskite-type phosphors, 10 Mn 4+ doped tungstate compounds containing WO6 octahedron, 11 Mn 4+ doped garnet phosphors, 12 and so on.…”