A high-light-harvesting-efficiency coumarin dye for stable dye-sensitized solar cells

A new high-light-harvesting-efficiency coumarin dye, exhibiting a high extinction coefficient and producing unity incident photon-to-electron conversion efficiency (IPCE) values in a broad spectral region, was developed for stable dye-sensitized solar cells (DSSC). The high light-harvesting efficiency (LHE) allows a very thin film to be used in the DSSC, which is important in reducing photovoltage loss due to an increased film resistance and charge recombination; in keeping a relatively high mechanical strength of the film when surrounded by liquid electrolyte during cell operation; and in cutting the total production cost. DSSCs with long-term stability, based on metal-free organic dyes and with a significant power-conversion efficiency, have been fabricated and operated under continuous light-soaking stress for up to 1000 h.