NOVELTY - Substituted benzotriazole compounds (A) are new.    USE - (A) are useful in wavelength conversion films, wavelength conversion luminescent mediums (all claimed) including optical light collection systems, fluorescence-based solar collectors, fluorescence-activated displays, and single-molecule spectroscopy and photovoltaic industry.    ADVANTAGE - (A) enhance solar harvesting efficiency of photovoltaic or solar cell devices. (A) exhibits desirable optical properties and good photo-stability with improved long wavelength conversion efficiency, high fluorescence quantum efficiency and light conversion effects.    DETAILED DESCRIPTION - Substituted benzotriazole compounds (A) of formulae (I)-(III) are new.    i = 0-100;    Ao, Af = alkyl, alkenyl, heteroalkyl, aryl, heteroaryl, amino, amido, cyclic amido, cyclic imido, alkoxy, carboxy or carbonyl (all optionally substituted);    A2 = alkylene, alkenylene, arylene, heteroarylene (all optionally substituted), ketone, ester or formamide group of formula (a);    Ar1 = aryl or heteroaryl (both optionally substituted); either    R1 = H, alkyl, alkenyl, aryl, heteroaryl, aralkyl or alkaryl; and    R2 = alkylene, alkenylene, arylene, heteroarylene (all optionally substituted) ketone or ester; or    R1R2 = ring;    D1, D2 = alkoxy, aryloxy, acyloxy, alkyl, aryl, heteroaryl, amino (all optionally substituted) H, amido, cyclic amido or cyclic imido;    L1 = alkylene, alkenylene, alkynylene, arylene or heteroarylene (all optionally substituted);    Z1, Z2 = -O-, -S-, -Se-, -Te-, -NR6-, -CR6=CR6- or -CR6=N-;    R6 = 1-6C alkyl, 1-10C aryl (both optionally substituted) or H;    j, k = 0-2; and    Y1, Y2 = aryl, alkyl, cycloalkyl, alkoxy or amino (all optionally substituted).    Provided that D1 and D2 are not both hydrogen. INDEPENDENT CLAIMS are included for:    (1) a wavelength conversion luminescent medium comprising an optically transparent polymer matrix and at least one luminescent dye comprising (A);    (2) a photovoltaic module comprising at least one photovoltaic device or solar cell (103), and the wavelength conversion luminescent medium, where the wavelength conversion luminescent medium is positioned such that the incident light passes through the wavelength conversion luminescent medium prior to reaching the photovoltaic device or solar cell; and    (3) a method for improving the performance of the photovoltaic device of solar cell, comprising applying a wavelength conversion luminescent medium directly onto the light incident side of the photovoltaic device or solar cell, or encapsulate the wavelength conversion luminescent medium in the photovoltaic device or solar cell.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of the photovoltaic device or solar cell.    Luminescent film (100)    Optical adhesive (101)    Light incident surface (102)    Solar cell. (103)