%0 Journal Article %A Shao, Guozheng %A Glaz, Micah S. %A Ma, Fei %A Ju, Huanxin %A Ginger, David S. %D 2014 %T Intensity-Modulated Scanning Kelvin Probe Microscopy for Probing Recombination in Organic Photovoltaics %U https://acs.figshare.com/articles/journal_contribution/Intensity_Modulated_Scanning_Kelvin_Probe_Microscopy_for_Probing_Recombination_in_Organic_Photovoltaics/2241415 %R 10.1021/nn5045867.s001 %2 https://acs.figshare.com/ndownloader/files/3877354 %K probe %K bulk heterojunction materials %K phosphonic acid monolayers %K intensity dependence %K OPV cell %K Organic PhotovoltaicsWe study surface photovoltage %K decay lifetimes %K device TPV %K background illumination %K test case %K Kelvin %K recombination lifetime %K indium tin oxide electrode %K charge extraction %K photovoltage decay lifetimes %K SKPM %K PCDTBT %K carrier lifetime %K recombination rates %K CE data %K frequency dependence %X We study surface photovoltage decays on sub-millisecond time scales in organic solar cells using intensity-modulated scanning Kelvin probe microscopy (SKPM). Using polymer/fullerene (poly[N-9″-heptadecanyl-2,7-carbazole-alt-5,5-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)]/[6,6]-phenyl C71-butyric acid methyl ester, PCDTBT/PC71BM) bulk heterojunction devices as a test case, we show that the decay lifetimes measured by SKPM depend on the intensity of the background illumination. We propose that this intensity dependence is related to the well-known carrier-density-dependent recombination kinetics in organic bulk heterojunction materials. We perform transient photovoltage (TPV) and charge extraction (CE) measurements on the PCDTBT/PC71BM blends to extract the carrier-density dependence of the recombination lifetime in our samples, and we find that the device TPV and CE data are in good agreement with the intensity and frequency dependence observed via SKPM. Finally, we demonstrate the capability of intensity-modulated SKPM to probe local recombination rates due to buried interfaces in organic photovoltaics (OPVs). We measure the differences in photovoltage decay lifetimes over regions of an OPV cell fabricated on an indium tin oxide electrode patterned with two different phosphonic acid monolayers known to affect carrier lifetime. %I ACS Publications