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Mitul A.F.,Center for Advanced Photovoltaics | Mohammad L.,Center for Advanced Photovoltaics | Vaagensmith B.,Center for Advanced Photovoltaics | Dubey A.,Center for Advanced Photovoltaics | And 2 more authors.
IEEE Journal of Photovoltaics | Year: 2015

In solution-processed tandem polymer solar cells, one of the most challenging parts is the optimization of interconnecting layers (ICLs) between subcells. In this study, ICLs were optimized for double- and triple-junction polymer solar cells. We investigated the robustness of PEDOT:PSS/AZO/PEIE ICL for tandem polymer solar cells. Solvent testing for ICL robustness showed a uniform coverage of the PEDOT:PSS layer when prepared without adding DMSO and IPA in PEDOT:PSS and with no use of additional filters. The performance of tandem polymer solar cells was investigated on different temperatures of interfacial layer. The PEDOT:PSS annealing temperature can be used from 120 °C to 130 °C, while aluminum-doped zinc oxide (AZO) temperature can be used from 120 °C to 150 °C. Lowering the annealing temperature in ICLs might help to fabricate triple-junction solar cells because they require more layers, and some low-bandgap polymers cannot sustain high temperature. However, reduction in annealing temperature in PEDOT:PSS, AZO, and PEIE led to lower FF and Jsc. A double-junction device Voc of 1.05 V and a triple-junction Voc of 1.4 V indicated that the ICLs worked effectively. © 2011-2012 IEEE.

Mohammad L.,Center for Advanced Photovoltaics | Farzan Mitul A.,Center for Advanced Photovoltaics | Sigdel S.,Center for Advanced Photovoltaics | Dubey A.,Center for Advanced Photovoltaics | And 4 more authors.
IEEE Journal of Photovoltaics | Year: 2015

In this paper, we demonstrate that low-temperature-processed aluminum-doped zinc oxide (AZO)/ethoxylated polyethylenimine (PEIE) electron transport layer (ETL) significantly improves the performance of poly[(4,4′-bis(2- ethylhexyl) dithieno[3,2-b:2′,3′-d]silole)-2,6-diyl-alt-(2,1,3 benzothiadiazole)-4,7-diyl] (PSBTBT)-based inverted organic solar cells. Different metal oxides, including zinc oxide (ZnO), AZO, ZnO/PEIE, and AZO/PEIE, were used as ETL. The optical and morphological properties of ZnO, AZO, PEIE, and their combination layers were investigated in order to find the favorable ETLs for inverted structure PSBTBT:PC70BM solar cells. Transient photocurrent, photoinduced charge extraction by linearly increasing voltage, and atomic force microscopy were performed to understand the effects of charge transport, recombination, and morphological changes on device performance. Among the various layers, including ZnO, AZO, ZnO/PEIE, and AZO/PEIE, the low-temperature-processed AZO/PEIE combination ETL was the best performing interface layer that achieved the highest device fill factor and energy conversion efficiency. © 2011-2012 IEEE.

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