LAMINATED FABRICATION OF POLYMERIC PHOTOVOLTAIC DIODES

Photoexcited electron transfer between donor and acceptor molecular se miconductors provides a method of efficient charge generation followin g photoabsorption, which can be exploited in photovoltaic diodes(1-3). But efficient charge separation and transport to collection electrode s is problematic, because the absorbed photons must be close to the do nor-acceptor heterojunction, while at the same time good connectivity of the donor and acceptor materials to their respective electrodes is required. Mixtures of acceptor and donor semiconducting polymers(3,4) (or macromolecules(5)) can provide phase-separated structures which go some way to meeting this requirement, providing high photoconductive efficiencies. Here we describe two-layer polymer diodes, fabricated by a lamination technique followed by controlled annealing, The resultin g structures provide good connectivity to the collection electrodes, a nd we achieve a short-circuit photovoltaic quantum efficiency of up to 29% at optimum wavelength, and an overall power conversion efficiency of 1.9% under a simulated solar spectrum. Given the convenience of po lymer processing, these results indicate a promising avenue towards pr actical applications for such devices.