TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The transparent material is a substrate comprising at least one material selected from indium tin oxide (ITO), tin oxide (TO), gallium indium tin oxide (GITO), zinc oxide (ZO), and zinc indium tin oxide (ZITO), glass polymers, and transparent conductive polymers comprising polyanaline (PANI).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preparation: No general method for preparation of the compound (I) is given. Preferred Compound: The compound (I) is amorphous or asymmetric. Preferred Method: The step of depositing involves at least one process selected from vacuum deposition and solution processing. The solution processing involves at least one technique selected from spin coating, spray coating, dip coating, or doctor's blading. The compound (I) is sublimed during vacuum deposition at least one time. The donor-acceptor heterojunction is formed by depositing the acceptor material over the donor material. The method further involves depositing at least one electron or exciton blocking material over the donor-acceptor heterojunction. The method further involves depositing at least one metal contact over the donor-acceptor heterojunction; and depositing at least one second compound (I) to form the donor-acceptor heterojunction; where the metal contact comprises a metal substitute, a non-metallic material or a metallic material chosen from Ag, Au, or Al. The donor-acceptor heterojunction is formed at an interface of a donor material comprising the compound (I) and an acceptor material comprising at least one compound selected from perylenes, pthalocyanines, porphyrins, napthalenes, fullerenes, or nanotubules. Preferred Components: The acceptor material comprises at least one compound selected from C60, C70, C84, 3,4,9,10-perylenetracarboxylic dianhydride (PTCDA), 3,4,9,10-perylenetracarboxylic diimide (PTCDI), 3,4,9,10-perylenetetracarboxylic-bis-benzimidazole (PTCBI), 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA), copper pthalocyanine (CuPc), or copper-hexadecafluoro-phthalocyanine (F16-CuPc). The donor-acceptor heterojunction comprises at least two different squaraines to provide more efficient light harvesting at wavelengths of 500-850 nm, when compared to a donor-acceptor heterojunction comprising, at most, one squaraine. The electron or exciton blocking material is chosen from bathocuproine (BCP), bathophenanthroline (BPhen), 3,4,9,10-perylenetetracarboxylicbis-benzimidazole (PTCBI), 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene (TPBi), tris(acetylacetonato)ruthenium(III) (RuAcaca3), or aluminum(III)phenolate (Alq2 OPH). SPECIFIC COMPOUNDS - 8 Compounds are specifically claimed as the compound (I) e.g. 2,4-bis(4-N-carbazolo-2,6-dihydroxyphenyl)squaraine (I'), 2,4-bis(4-N-phenothiazino-2,6-dihydroxyphenyl)squaraine (PTSQ), 2,4-bis(4-(N,N-diphenylamino)-2,6-dihydroxyphenyl)squaraine (DPSQ), 2,4-bis(4-(N-Phenyl-1-naphthylamino)-2,6-dihydroxyphenyl) squaraine (1NPSQ), 2,4-bis(4-(N-Phenyl-2-naphthylamino)-2,6-dihydroxyphenyl) squaraine (2NPSQ).    EXAMPLE - No suitable example given.