Near infrared up-conversion in organic photovoltaic devices using an efficient Yb3+:Ho3+ Co-doped Ln2BaZnO5 (Ln = Y, Gd) phosphor

The first detailed study that combines the use of a new generation of high-efficiency Yb3+:Ho3+ co-doped Y2BaZnO5 near-infrared up-converting phosphors with organic photovoltaic devices is reported. We show that it is possible to obtain a J(sc) of 16 mu A cm(-2) under 986 nm illumination (similar to 390 mW cm(-2) corresponding to similar to 37 suns) leading to an up-conversion external quantum efficiency (eta(UC)(EQE)) of 0.0052%. Through modification of the organic photovoltaic devices to incorporate transparent electrodes we show that eta(UC)(EQE) could be increased to 0.031 %, matching that achieved in amorphous-Si:H PV cells. Accounting for the full spectral range that may be absorbed by the phosphor (similar to 870-1030 nm) yields an up-conversion power conversion efficiency (eta(UC)(PCE)) of 0.073% which again could be improved to 0.45% using transparent electrodes. This technique for utilizing the near-infrared spectral region may therefore offer a potential route to improving the performance of organic photovoltaic devices as research into discovering high-efficiency up-converting phosphors continues to provide improved materials. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4704687]