TECHNOLOGY FOCUS - ELECTRONICS - Preferred Components: The low energy gap material is a group II-VI semiconductor. The middle energy gap material is a group III-V semiconductor. The high energy gap material is a group IV semiconductor.Preferred Device: The nanocrystals are randomly or uniformly dispersed in the conductive material, or are dispersed in the conductive material in the manner of concentration gradient. The shape of nanocrystal is a tetrapod. The photoactive layer is electrically connected to the first electrode and the second electrode. The top substrate or the bottom substrate further comprises a carrier transfer layer. The photoactive layer comprises (wt.%) the nanocrystals (A) (70-90) and the conductive material (10-30).Preferred Components: The at least one of the top substrate and the bottom substrate is a flexible substrate.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The high energy gap material is selected from a group consisting of MgS, MgSe, MgTe, MnS, MnSe, MnTe, ZnS, ZnSe, GaN, SiC, TiO2, C derivatives, and/or their alloy. The middle energy gap material is selected from ZnTe, CdS, CdSe, CdTe, HgS, HgI2, PbI2, InP, GaP, TlBr, C derivatives, and/or their alloy (preferably CdSe). The low energy gap material is selected from PbS, PbSe, PbTe, HgSe, HgTe, InAs, InSb, GaSb, Si, Ge, and/or their alloy. The low energy gap material, middle energy gap material, or the high energy gap material is an inorganic light absorption material (preferably PbS, PbSe, and/or TiO2). The second shell comprises PbSe. The core is a quantum dot, and comprises ZnSe, ZnSe/ZnS, ZnSe/ZnSeS, ZnS, or ZnTe (preferably ZnSe, ZnS, or ZnTe; especially ZnSe or ZnTe). The conductive material comprises an inorganic conductive material.Preferred Composition: The shape of the nanocrystal is a rod, a tetrapod, a radial form, an arrow, a teardrop, and/or an irregular form (preferably a rod, a tetrapod, and/or a radial form).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The conductive material comprises an organic conductive material (preferably N,N'-di(naphthalen)-N,N'-diphenyl-benzidine (NPB); N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)benzidine (alpha-NPB); N,N'-di(naphthalene-1-yl)N,N'-diphenyl-9,9,-dimethyl-fluorene (DMFL-NPB); N,N'-di(naphthalene-1-yl)-N,N'-diphenyl-spiro (Spiro-NPB); N,N'-Bis-(3-methylphenyl)-N,N'-bis-(phenyl)-benzidine (TPD); N,N'-bis-(3-methylphenyl)-N,N'-bis-(phenyl)-spiro (Spiro-TPD); N,N'-bis-(3-methylphenyl)-N,N'-bis-(phenyl)-9,9-diphenyl-fluorene (DMFL-TP-D); 1,3-bis(carbazol-9-yl)-benzene (MCP); 1,3,5-tris(carbazol-9-yl)-benzene (TCP); N,N,N',N'-tetrakis(naphth-1-yl)-benzidine (TNB); poly(N-vinyl carbazole) (PVK); poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV); poly(2-Methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene-co-4,4'-bisphenylenevinylene) (MEH-BP-PPV); poly((9,9-dioctylfluoren-2,7-diyl)-co-(1,4-diphenylene-vinylene-2-methoxy-5-(2-ethylhexyloxy)benzene)) (PF-BV-ME); poly((9,9-dioctylfluoren-2,7-diyl)-co-(2,5-dimethoxy benzen-1,4-diyl)) (PF-DMOP); poly((9,9-dihexylfluoren-2,7-diyl)-alt-co-(benzen-1,4-diyl)) (PFH); poly((9,9-dihexylfluoren-2,7-diyl)-co-(9-ethylcarbazol-2,7-diyl)) (PFH-EC); poly((9,9-dihexylfluoren-2,7-diyl)-alt-co-(2-methoxy-5-(2-ethylhexyloxy)-phenylen-1,4-diyl)) (PFH-MEH); poly((9,9-dioctylfluoren-2,7-diyl) (PFO); poly((9,9-di-n-octylfluoren-2,7-diyl)-co-(1,4-vinylenephenylene)) (PF-PPV); poly((9,9-dihexylfluoren-2,7-diyl)-alt-co-(benzen-1,4-diyl)) (PF-PH); poly((9,9-dihexylfluoren-2,7-diyl)-alt-co-(9,9'-spirobifluoren-2,7-diyl)) (PF-SP); poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine(poly-TPD) poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl) benzidine (poly-TPD-POSS); poly((9,9-dihexylfluoren-2,7-diyl)-co-(N,N'-di(4-butylphenyl)-N,N'-diphenyl-4,4'-diyl-1,4-diamino benzene)) (TAB-PFH); N,N'-bis(phenanthren-9-yl)-N,N'-diphenylbenzidine (PPB); tris-(8-hydroxy quinoline)-aluminum(Alq3); bis-(2-methyl-8-quinolinolate)-4-(phenylphenolato)-aluminium (BAlq3); 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP); 4,4'-bis(carbazol-9-yl) biphenyl (CBP); 3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ); MEH-PPV; MEH-BP-PPV; PF; PF-BV-MEH; PF-DMOP; PFH; PFH-EC; PFH-MEH; PFO; PFOB; PF-PPV; PF-PH; PF-SP; poly-TPD; poly-TPD-POSS; TAB-PFH; and/or PPB). EXAMPLE - A nanocrystal was prepared by providing a core of ZnSe. Then, a second precursor solution and a third precursor solution were applied to react with the core to form the first shell and the second shell, as follow: Selenium (Se) powder (1 mmol) was dried in a vacuum to remove moisture. The dried selenium powders, tri-n-octylphosphine (TOP) (2 ml), and toluene (2 ml) were mixed and dispersed by supersonic vibration for 30 minutes under an inert atmosphere to form a TOPSe solution, as a colorless liquid. Zinc oxide powder (1 mmol) was heated to 120degreesC under inert atmosphere to remove moisture. After cooling to room temperature, benzoic acid (stearic acid) (40 mmol) and of tri-n-octylphosphine oxide (TOPO) (20 mmol) were added. The mixture was then heated to 150degreesC and maintained for 20 minutes to form a transparent liquid. Subsequently, the transparent liquid was heated to 300degreesC. After the temperature of the transparent liquid has risen to 300degreesC through heating, the prepared TOPSe solution was added to the transparent liquid, and kept reacting for 5 minutes to form a mixture that comprises ZnSe cores. After the ZnSe cores were formed, the mixture was cooled to 100degreesC. Then, a precursor solution of the first shell containing CdO (1 mmol), stearic acid (3 mmol), and TOPO (3 mmol), was added into the mixture. The mixture was then heated to 320degreesC and maintained for 30 minutes. Subsequently, a TOPSSe solution containing TOP (4 ml), sulfur (1 mmol), selenium (1 mmol), and toluene (2 ml), was added into the mixture under an inert atmosphere and kept reacting for 10 minutes to grow the first shell of CdSe from the cores. After the first shell is formed, the mixture is cooled to 100degreesC, and a precursor solution of the second shell containing PbO (0.3 mmol), stearic acid (1 mmol), and TOPO (1 mmol), was then added into the mixture. The mixture was heated to 280degreesC and maintained for 30 minutes. Finally, a TOPSe solution containing TOP (1 ml), selenium (0.2 mmol), and toluene (2 ml), was added to the mixture under an inert atmosphere and kept reacting for 5-10 minutes to grow the second shell of PbSe from the cores and the nanocrystals. A photovoltaic device was prepared as follows. A photoactive layer contained (wt.%) the nanocrystals (tetrapod-shaped) (85), and poly(3-hexylthiophene) (P3HT) (15) as the organic conductive material. A top substrate included a substrate and a first electrode. A bottom substrate included a substrate, a second electrode, and a carrier transfer layer. The first electrode was a cathode composed of aluminum, and the second electrode was an anode composed of indium-tin oxide. The material of the carrier transfer layer was a combination of poly(3,4-ethylene dioxythiophene) and poly(styrenesulfonate. The photovoltaic device was then connected to a load/device to form a current circuit, and illuminated by an external light source. Free electrons or electron/hole pairs were generated in the photoactive layer, and a resulting current flow was then exploited in load/device.