High efficiency inverted polymeric bulk-heterojunction solar cells with hydrophilic conjugated polymers as cathode interlayer on ITO

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• 作者：Yongxiang Zhu ; Xiaofeng Xu ; Lianjie Zhang ; Junwu Chen ; ^{psjwchen@scut.edu.cn} ; Yong Cao
• 关键词：Inverted solar cell ; Hydrophilic conjugated polymer ; Cathode interlayer polymer ; Interface modification ; Low band gap polycarbazole
• 刊名：Solar Energy Materials and Solar Cells
• 出版年：2012
• 出版时间：February, 2012
• 年：2012
• 卷：97
• 期：Complete
• 页码：83-88
• 全文大小：438 K

文摘

In this work, alcohol-soluble 2,7-carbazole-1,4-phenylene copolymers PCP-NOH and PCP-EP, comprising surfactant-like diethanolamino and phosphonate end groups on the side chains, respectively, were utilized as cathode interlayer on ITO to construct inverted solar cells based on a low band gap poly(2,7-carbazole) (PCDTBT) as the polymer donor and [6,6]-phenyl C₇₁-butyric acid methyl ester (PC₇₁BM) as the acceptor. The work functions of ITO were shifted to ?.2 and ?.3 eV by PCP-NOH and PCP-EP, respectively, which can well match the LUMO level of PC₇₁BM for good electron extraction. The power conversion efficiency (PCE) of the inverted solar cells without the cathode interlayer was only 1.63 % , because of very low open-circuit voltage (V_oc, 0.48 V) and fill factor (FF, 36.9 % ). Using PCP-NOH and PCP-EP as cathode interlayers significantly improved V_oc to 0.88 V and FF to ?8 % , giving PCEs of 5.39 % and 5.48 % , respectively. The increasing extents of PCEs by the interlayers are over 230 % . The PCEs achieved by PCP-NOH and PCP-EP belong to the top device performances so far reported for the inverted PVCs with an organic cathode interlayer. Our results suggest that hydrophilic conjugated polymers are promising candidates as a cathode interlayer in high efficiency inverted solar cells through the modification of interface contacts.