**2. Overview of LED technology used postharvest in horticultural crops**

An LED consists of a semiconductor with a positive and negative junction, called p- and n-type, respectively. When an LED is connected to a power source, a flow of current starts from the positive (p-type) to the negative (n-type) junction, ultimately resulting in the flow of electrons, which causes light emission at a certain wavelength [7, 15]. The color of light emitted by the LED is determined by the band gap energy of the semiconductor material. **Figure 2** depicts the LED lighting system. Improved technology has enabled LEDs to be used in the postharvest preservation of fruit and vegetables. The unique and advantageous properties of LEDs have resulted in their use in postharvest storage of fresh fruit and vegetables [16]. The monochromatic nature, high photon efficiency, low radiant heat, durability, and prevention of thermal degradation of LEDs are favorable characteristics that make them beneficial in fruit and vegetable postharvest storage [17]. Moreover, the monochromatic nature of LEDs allows horticulturists to select specific wavelengths for the storage and preservation of horticultural produce [17]. Furthermore, LEDs operate at low direct current voltages and temperature, and their operation does not involve the use of toxic, environmentally unfriendly substances. As a result, the postharvest application of LEDs in the agricultural sector has expanded over the past years.

#### **Figure 2.** *Emission of photons by light-emitting diodes (LEDs), adopted from [7].*
