NOVELTY - Organic solar cell (400) comprises substrate (402) having first electrode (404) on it, hole transport layer overlying the first electrode, metal layer having first pattern in the hole transport layer, active layer having first organic semiconductor film having second pattern complementary to first pattern and overlying the metal layer and hole transport layer, and second organic semiconductor film having first pattern aligned to the first pattern of metal layer and overlying the first organic semiconductor film; and second electrode overlying active layer.    USE - As organic solar cell (claimed) useful for converting light energy to electric energy.    ADVANTAGE - The organic solar cell has high photoelectric conversion efficiency. The solar cell has patterned metal layer, which has a pattern complementary to and aligned to/interlocked with the patterns of the two organic semiconductor films of opposite conductive types of the active layer, thus the configuration of the light-absorbing materials of the active layer is correspondingly aligned to the specific locations where the magnetic field is enhanced by the localized surface plasmons excited by the patterned metal layer, hence the light-absorbing efficiency of the active layer and the generation of the photocurrent is increased; as a result, the photoelectric conversion efficiency of the organic solar cell is achieve maximum efficiency. The method of forming the organic solar cell is simple method. The pattern of the active layer is directly aligned with or self-aligned to the region of the patterned metal layer such that it effectively avoids and reduces the complexity of the process, thus the organic solar cell device is both easily formed and cost-effective.    DETAILED DESCRIPTION - An organic solar cell (400) comprises a substrate (402) having a first electrode (404) on it; a hole transport layer overlying the first electrode; a metal layer having a first pattern in the hole transport layer; an active layer having a first organic semiconductor film having a second pattern complementary to the first pattern and overlying the metal layer and the hole transport layer, and a second organic semiconductor film having the first pattern substantially aligned to the first pattern of the metal layer and overlying the first organic semiconductor film; where the first and second organic semiconductor have opposite conductive types; and a second electrode overlying the active layer. An INDEPENDENT CLAIM is included for Forming an organic solar cell involving providing a substrate having a first electrode; forming a hole transport layer and a metal layer on the first electrode, where the metal layer has a first pattern; forming an active layer on the hole transport layer comprising forming a first organic semiconductor film having a second pattern complementary to the first pattern on the metal layer and the hole transport layer, and forming a second organic semiconductor film having the first pattern substantially aligned to the first pattern of the metal layer on the first organic semiconductor film; and forming a second electrode on the active layer.    DESCRIPTION OF DRAWING(S) - The figure shows cross-sectional view of organic solar cell.    Organic solar cell (400)    Substrate (402)    First electrode (404)