10.1021/acsami.6b15436.s001 Pengzhi Guo Pengzhi Guo Guoping Luo Guoping Luo Qiang Su Qiang Su Jianfeng Li Jianfeng Li Peng Zhang Peng Zhang Junfeng Tong Junfeng Tong Chunyan Yang Chunyan Yang Yangjun Xia Yangjun Xia Hongbin Wu Hongbin Wu Boosting Up Performance of Inverted Photovoltaic Cells from Bis(alkylthien-2-yl)dithieno[2,3‑<i>d</i>:2′,3′‑<i>d</i>′]benzo[1,2‑<i>b</i>:4′,5′‑<i>b</i>′]di thiophene-Based Copolymers by Advantageous Vertical Phase Separation American Chemical Society 2017 XPS PDTBDT-FBT devices configuration Inverted Photovoltaic Cells power conversion efficiencies PCE polymers cathode modification layers light harvesting characteristics PC 71 BM Advantageous Vertical Phase Separation PDTBDT-BT electron acceptor moieties phase separation ITO electron donor moieties cathode modification interlayer AM X-ray photoelectron spectroscopy PFN 2017-03-09 00:00:00 Journal contribution https://acs.figshare.com/articles/journal_contribution/Boosting_Up_Performance_of_Inverted_Photovoltaic_Cells_from_Bis_alkylthien-2-yl_dithieno_2_3_i_d_i_2_3_i_d_i_benzo_1_2_i_b_i_4_5_i_b_i_di_thiophene-Based_Copolymers_by_Advantageous_Vertical_Phase_Separation/4765690 The photovoltaic cells (PVCs) from conjugated copolymers of PDTBDT-BT and PDTBDT-FBT with 5,10-bis­(4,5-didecylthien-2-yl)­dithieno­[2,3-<i>d</i>:2′,3′-<i>d</i>′]­benzo­[1,2-<i>b</i>:4,5-<i>b</i>′]­dithiophene as electron donor moieties and benzo­thiadiazole and/or 5,6-difluorobenzo­thiadiazole as electron acceptor moieties are optimized by employing alcohol-soluble PFN (poly­(9,9-bis­(3′-(<i>N</i>,<i>N</i>-dimethyl­amino)­propyl)-2,7-fluorene)-<i>alt</i>-2,7-(9,9-dioctyl­fluorene)) as cathode modification interlayer. The power conversion efficiencies (PCEs) of inverted PVCs (<i>i-</i>PVCs) from PDTBDT-BT and PDTBDT-FBT with devices configuration as ITO/PFN/active layer/MoO<sub>3</sub>/Ag are increased from 4.97% to 8.54% and 5.92% to 8.74%, in contrast to those for the regular PVCs (<i>r-</i>PVCs) with devices configuration as ITO/PEDOT:PSS/active layer/Ca/Al under 100 mW/cm<sup>2</sup> AM 1.5 illumination. The optical modeling calculations and X-ray photoelectron spectroscopy (XPS) investigations reveal that the <i>r-</i>PVCs and <i>i-</i>PVCs from the copolymers exhibit similar light harvesting characteristics, and the enhancements of the PCEs of the <i>i-</i>PVCs from the copolymers are mainly contributed to the favorable vertical phase separation as the strongly polymer-enriched top surface layers and slightly PC<sub>71</sub>BM (phenyl-C<sub>71</sub>-butyric acid methyl ester)-enriched bottom surface layers are correspondingly connected to the anodes and cathodes of the <i>i-</i>PVCs, while they are opposite in the <i>r-</i>PVCs. As we known, it is the first time to experimentally verify that the <i>i-</i>PVCs with alcohol-soluble conjugated polymers cathode modification layers enjoy favorable vertical phase separation.