NOVELTY - An organic solar cell (100) comprises a substrate (102) having a first electrode (104) formed on it; an organic photoactive layer (500) overlying the first electrode, where the organic photoactive layer includes a crystalline first organic molecule (502) of a first conductive type; and second molecule of a second conductive type opposite to the first conductive type; and second electrode (600) overlying the organic photoactive layer, where the substrate comprises glass and/or transparent plastic substrate.    USE - As organic solar cell (claimed).    ADVANTAGE - The organic solar cell has following advantages: (1) large quantities of crystal nuclei are formed at a low temperature and the molecules adjacent to the crystal nuclei are rapidly depleted. Thus, compared to prior art, non-crystalline molecules are significantly reduced and excessive aggregations formed by the non-crystalline molecules are also eliminated, thus increasing the heterojunction and improving the light-to-energy conversion efficiency; (2) Due to the formation of the dense crystalline network, current is transported more efficiently; (3) The morphology of the organic photoactive layer is very stable. The remaining non-crystalline does not migrate and aggregate because the non-crystalline molecules are depleted while forming the crystalline network. The non-crystalline molecules are constrained by the crystalline network. Thus, a stable morphology of the organic photoactive layer results in a stable performance of the organic solar cell.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for forming organic solar cell involving providing a substrate with a first electrode formed on it, coating a first organic molecule and second molecule onto the first electrode to form a wet film, where the first organic molecule has a first conductive type and the second molecule has a second conductive type opposite to the first conducive type, placing the wet film at a first temperature such that a crystal nucleus from the first organic molecule is formed, and drying the wet film to form a dry film; placing the dry film at a second temperature for crystal growth, to form an organic photoactive layer including the first organic molecule of a crystalline phase and the second molecule; and forming a second electrode on the organic photoactive layer.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of organic solar cell.    Organic solar cell (100)    Substrate (102)    Organic photoactive layer (500)    Crystalline first organic molecule (502)    Second electrode (600)