A comprehensive review of current trends and future perspective of quantum dots regarding their optical and photoswitchable properties

Quantum dots (QDs) are widely employed in photovoltaic applications like solar cells and other devices, as their optical characteristics may be tailored by varying their particle size. When the dimensions of QDs become less than de Broglie wavelength of the electron, they show properties like a particle in a box known as the quantum confinement effect, which depends on particle size. Binary QDs are susceptible to photodegradation and photobleaching in contrast to ternary and quaternary QDs. Moreover, QDs with ternary composition have a wide window optical absorption and are used as broadened gap window materials in photoinduced devices as well as in heterojunction solar cells. For quaternary QDs, the band gap is controlled by varying the elemental compositions and changes in particle size. These two strategies can be regarded as a convenient reason for using these materials in solar cells to prevent absorption loss and hence increase the short-circuit current. These nanoparticles exhibit a tunable emission window, a property that can be exploited in photochromic switches. The attachment of photochromic components to nanoparticles with binary and ternary composition has been exploited to modulate their photoluminescence intensity and is applicable in various biological and optical applications. Efficient fluorophore-photo chrome dyads can be designed from QDs with binary, ternary, and quaternary compositions. Moreover, countless attempts have been made to enhance and improve the optical and photoswitchable characteristics of QDs. This review article encompasses three areas: (a) optical characteristics of binary, ternary, and quaternary QDs; (b) photochromism; (c) photoswitchable characteristics of QDs. We finally jump to conclusions and discuss future perspectives on the further improvement of photo-switchable QDs.