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Triarylamine-based polymers with different functional groups were synthetized as hole-transport materials (HTMs) for perovskite solar cells (PSCs). The novel materials enabled efficient PSCs without the use of chemical doping (or additives) to enhance charge transport. Devices employing poly(triarylamine) with methylphenylethenyl functional groups (V873) showed a power conversion efficiency of 12.3 %, whereas widely used additive-free poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) demonstrated 10.8 %. Notably, devices with V873 enabled stable PSCs under 1 sun illumination at maximum power point tracking for approximately 40 h at room temperature, and in the dark under elevated temperature (85 °C) for more than 140 h. This is in stark contrast to additive-containing devices, which degrade significantly within the same time frame. The results present remarkable progress towards stable PSC under real working conditions and industrial stress tests. [ABSTRACT FROM AUTHOR]

Star-shaped charge-transporting materials with a triphenylamine (TPA) core and various phenylethenyl side arm(s) were obtained in a one-step synthetic procedure from commercially available and relatively inexpensive starting materials. Crystallinity, glass-transition temperature, size of the π-conjugated system, energy levels, and the way molecules pack in the solid state can be significantly influenced by variation of the structure of these side arm(s). An increase in the number of phenylethenyl side arms was found to hinder intramolecular motions of the TPA core, and thereby provide significant enhancement of the fluorescence quantum yield of the TPA derivatives in solution. On the other hand, a larger number of side arms facilitated exciton migration through the dense side-arm network formed in the solid state and, thus, considerably reduces fluorescence efficiency by migration-assisted nonradiative relaxation. This dense network enables charges to move more rapidly through the hole-transport material layer, which results in very good charge drift mobility ( μ up to 0.017 cm2 V −1 s−1). [ABSTRACT FROM AUTHOR]

The Inside Back Cover picture shows a perovskite solar cell in a multilayer architecture containing a fluorine‐doped tin oxide substrate, mesoporous TiO2 and triple‐cation perovskite active layer, new dopant/additive‐free triarylamine polymeric hole‐transport material, and gold electrode. Despite the absence of dopants/additives, the use of this new hole‐transport material (pink layer) yields highly efficient perovskite solar cells enabling stable devices even at elevated temperatures (85°C). More details can be found in the Communication by Matsui et al. on page 2567 in Issue 18, 2016 (DOI: 10.1002/cssc.201600762). [ABSTRACT FROM AUTHOR]