“…Small-molecule semiconductors with narrowband absorption properties have played a key role in the development of organic narrowband photodetectors (see section 5.1). A significant number of them are drawn or derived from compounds originally developed as industrial colourants, laser dyes, or fluorescent probese.g., blue-absorbing coumarins [22,[44][45][46][47], green-absorbing rhodamines [44,45,[48][49][50][51] and quinacridones [11,47,[52][53][54][55][56][57][58][59][60][61][62][63], green-and red-absorbing phthalocyanine metal/metalloid complexes and derivatives [11, 44, 45, 47, 49, 54-56, 58, 61, 64-70], and green-, red-, and NIR-absorbing squaraines [23,[71][72][73] ( figure 4(b)). It is noteworthy that some narrowband-absorbing small molecules are able to form aggregates (Jand H-aggregates) featuring particularly narrow and intense absorption bands (FWHM α <20 nm, α up to 10 6 cm −1 ), a property that is very attractive for narrowband photodetection [24,[74][75][76][77][78][79].…”