We introduce a p-i-n type heterojunction architecture for organic solar cells where the active\nregion is sandwiched between two doped wide-gap layers. The term p-i-n means here a\nlayer sequence in the form p-doped layer, intrinsic layer and n-doped layer. The doping is\nrealized by controlled coevaporation using organic dopants and leads to conductivities of 10-4\nto 10-5 S/cm in the p- and n-doped wide gap layers, respectively. The photoactive layer is\nformed by a mixture of phthalocyanine zinc (ZnPc) and the fullerene C60 and shows mainly\namorphous morphology. As a first step towards p-i-n structures, we show the advantage of\nusing wide-gap layers in M-i-p type diodes (metal layer – intrinsic layer - p-doped layer). The\nsolar cells exhibit a maximum external quantum efficiency of 40% between 630nm and\n700nm wavelength.\nWith the help of an optical multilayer model, we optimize the optical properties of the solar\ncells by placing the active region at the maximum of the optical field distribution. The results\nof the model are largely confirmed by the experimental findings. For an optically optimized\ndevice, we find an internal quantum efficiency of around 82% under short-circuit conditions.\nAdding a layer of 10nm thickness of the red material N,N'-dimethylperylene-3,4:9,10-\ndicarboximide (Me-PTCDI) to the active region, a power conversion efficiency of 1.9% for a\nsingle cell is obtained. Such optically thin cells with high internal quantum efficiency are an\nimportant step towards high efficiency tandem cells.