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Interfaces between the photoactive layers and electrodes play critical roles in controlling the performance of optoelectronic devices. Herein, a novel nonconjugated polymer additive (nPA), poly(2-vinylpyridine) (P2VP), is reported for modifying the interfaces between the bulk-heterojunction (BHJ) and cathode/metal oxide (MO) layers. The P2VP nPA enables remarkably enhanced power conversion efficiencies (PCEs) and ambient stability in different types of polymer solar cells (PSCs). Importantly, interfacial engineering can be achieved during deposition of the P2VP nPA-containing BHJ active layer via simple, one-step solution processing. The P2VP nPA has much higher surface energy than the BHJ active components and stronger interaction with the surface of MO, which affords spontaneous vertical phase separation from the BHJ layer on the MO surface by one-step solution processing. The self-assembled P2VP layer substantially reduces the work function and surface defect density of MO, thereby minimizing the charge-extraction barrier and increasing the PCEs of the PSCs significantly, i.e., PTB7-Th:PC71BM (10.53%→11.14%), PTB7:PC71BM (7.37%→8.67%), and PTB7-Th:P(NDI2HD-T) all-PSCs (5.52%→6.14%). In addition, the lifetimes of the PSCs are greatly improved by the use of the P2VP nPA. [ABSTRACT FROM AUTHOR]

Abstract: A perfluorinated compound, 4-amino-2-(trifluoromethyl)benzonitrile ( ATMB ), was applied as an additive to polymer solar cells (PSCs) with P3HT [poly(3-hexylthiophene)]:PCBM [[6,6]-phenyl-C61-butyric acid methyl ester] blend films. The addition of 6wt% ATMB to a P3HT:PCBM layer led to an increased power conversion efficiency of 5.03% due to the enhanced short circuit current and fill factor when compared with that of the reference cell without an additive. On the other hand, the devices with 4-aminobenzonitrile as an additive, not containing fluorine atoms in the molecule, displayed lower PCEs than that of the reference cell. The UV–visible absorption spectra, X-ray measurements and carrier mobility studies revealed that ATMB facilitated ordering of the P3HT chains, resulting in higher absorbance, larger crystal size of P3HT and enhanced hole mobility. XPS depth profiling measurements also showed that the additive molecules were predominantly positioned in the range of 25nm under the surface of the P3HT:PCBM film, leading to improved fill factor. [Copyright &y& Elsevier]

In article number 1602812, Jung‐Yong Lee, Bumjoon J. Kim, and co‐workers investigate nonconjugated polymer additives (nPAs) for highly efficient and stable polymer solar cells (PSCs). The P2VP nPA self‐assembles vertically on the ZnO surface via a single coating process for the deposition of active materials. The self‐assembled P2VP reduces the work function and surface defect density of ZnO, which leads to efficient and stable PSCs with up to 11.14% efficiency. [ABSTRACT FROM AUTHOR]