Prof Henry Snaith FRS

Abstract:

Recently, inorganic and hybrid light absorbers such as quantum dots and organometal halide perovskites have been studied and applied in fabricating thin-film photovoltaic devices because of their low-cost and potential for high efficiency. Further boosting the performance of solution processed thin-film solar cells without detrimentally increasing the complexity of the device architecture is critically important for commercialization. Here, we demonstrate photocurrent and efficiency enhancement in meso-superstructured organometal halide perovskite solar cells incorporating core-shell Au@SiO2 nanoparticles (NPs) delivering a device efficiency of up to 11.4%. We attribute the origin of enhanced photocurrent to a previously unobserved and unexpected mechanism of reduced exciton binding energy with the incorporation of the metal nanoparticles, rather than enhanced light absorption. Our findings represent a new aspect and lever for the application of metal nanoparticles in photovoltaics and could lead to facile tuning of exciton binding energies in perovskite semiconductors.

Abstract:

Chemical doping is a powerful method to improve the charge transport and to control the conductivity in organic semiconductors (OSs) for a wide range of electronic devices. We demonstrate protic ionic liquids (PILs) as effective p-dopant in both polymeric and small molecule OSs. In particular, we show that PILs promote single electron oxidation, which increases the hole concentration in the semiconducting film. The illustrated PIL-doping mechanism is compatible with materials processed by solution and is stable in air. We report the use of PIL-doping in hybrid solar cells based on triarylamine hole transporting materials, such as 2,2',7,7'-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9'-spirobifluorene (spiro-OMeTAD). We show improved power conversion efficiency by replacing lithium salts, typical p-dopants for spiro-OMeTAD, with PILs. We use photovoltage-photocurrent decay and photoinduced absorption spectroscopy to establish that significantly improved device performance is mainly due to reduced charge transport resistance in the hole-transporting layer, as potentiated by PIL-doping.

Abstract:

Transient mobility spectroscopy (TMS) is presented as a new tool to probe the charge carrier mobility of commonly employed organic and inorganic semiconductors over the relevant range of charge densities. The charge density dependence of the mobility of semiconductors used in hybrid and organic photovoltaics gives new insights into charge transport phenomena in solid state dye sensitized solar cells.

Abstract:

Transient mobility spectroscopy (TMS) is presented as a new tool to probe the charge carrier mobility of commonly employed organic and inorganic semiconductors over the relevant range of charge densities. The charge density dependence of the mobility of semiconductors used in hybrid and organic photovoltaics gives new insights into charge transport phenomena in solid state dye sensitized solar cells. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.