An Efficient Bulk-Heterojunction Photovoltaic Cell Based on Energy Transfer in Graded-Bandgap Polymers


  • K.S.N. acknowledges the Department of Information Technology for partial financial support. D.G. thanks the Council of Scientific and Industrial Research, Government of India, for a Senior Research Fellowship. Supporting Information is available online from Wiley InterScience or from the author.


It is demonstrated that the energy transfer from low-conjugated (LC) poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene] (MEHPPV) to high-conjugated (HC) MEHPPV, coupled with significant electron transfer from HC-MEHPPV to an acceptor species, offers a viable route for an efficient photodiode over a wide spectral range. An enhanced incident-photon-to-current conversion efficiency (IPCE) of 19 % over a wide spectral range and a power-conversion efficiency (ηP) of 1 % (under monochromatic illumination at λ ∼ 530 nm and a power density of ca. 1 mW cm–2) are achieved in a ternary polymer-blend film that consists of HC-MEHPPV (low bandgap), LC-MEHPPV (high bandgap), and an acceptor polymer, cyanoPPV (CNPPV), in an optimized ratio. The decisive role of the morphology that emerges during phase separation in the polymer blend is demonstrated by wide-field photocurrent imaging.