Prof Henry Snaith FRS

Abstract:

The power conversion efficiency of hybrid solid-state solar cells has more than doubled from 7 to 15% over the past year. This is largely as a result of the incorporation of organometallic trihalide perovskite absorbers into these devices. But, as promising as this development is, long-term operational stability is just as important as initial conversion efficiency when it comes to the development of practical solid-state solar cells. Here we identify a critical instability in mesoporous TiO₂-sensitized solar cells arising from light-induced desorption of surface-adsorbed oxygen. We show that this instability does not arise in mesoporous TiO₂-free mesosuperstructured solar cells. Moreover, our TiO₂-free cells deliver stable photocurrent for over 1,000 h continuous exposure and operation under full spectrum simulated sunlight.

Abstract:

A simple strategy is presented to determine the pore-filling fraction of the hole-conductor 2,2-7,7-tetrakis-N,N-di-pmethoxyphenylamine-9,9- spirobifluorene (spiro-OMeTAD) into mesoporous photoanodes in solid-state dye-sensitized solar cells (ss-DSCs). Based on refractive index determination by the film's reflectance spectra and using effective medium approximations the volume fractions of the constituent materials can be extracted, hence the pore-filling fraction quantified. This non-destructive method can be used with complete films and does not require detailed model assumptions. Pore-filling fractions of up to 80% are estimated for optimized solid-state DSC photoanodes, which is higher than that previously estimated by indirect methods. Additionally, transport and recombination lifetimes as a function of the pore-filling fraction are determined using photovoltage and photocurrent decay measurements. While extended electron lifetimes are observed with increasing pore-filling fractions, no trend is found in the transport kinetics. The data suggest that a pore-filling fraction of greater than 60% is necessary to achieve optimized performance in ss-DSCs. This degree of pore-filling is even achieved in 5 μm thick mesoporous photoanodes. It is concluded that pore-filling is not a limiting factor in the fabrication of "thick" ss-DSCs with spiro-OMeTAD as the hole-conductor. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Abstract:

Device optimization and ultrafast absorption spectroscopic investigations on the role of semiconducting polymer as hole-transport layer in solid-state dye sensitized solar cells suggest their dual role of dye-regeneration and light-antenna assisting in improved photoconversionefficiencies.© 2012 OSA.

Abstract:

Device optimization and ultrafast absorption spectroscopic investigations on the role of semiconducting polymer as hole-transport layer in solid-state dye sensitized solar cells suggest their dual role of dye-regeneration and light-antenna assisting in improved photoconversion-efficiencies. © 2012 OSA.