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Two dopant-free hole transporting materials (HTMs) comprising a planar indacenodithiophene (IDT) core with different alkyl chains (either C4 or C6) and electron-rich methoxytriphenylamine (TPA) side arms were synthesized (namely IDTC4-TPA and IDTC6-TPA, respectively) and successfully employed in CH3NH3PbI3 perovskite solar cells. These HTMs can be obtained from relatively cheap starting materials by adopting a facile preparation procedure that does not use expensive and complicated purification techniques. In the crystal lattice, each of these molecules interacted with either the CH/π or CH/O hydrogen bonds. At the same time, the IDTC6 backbone enables a tight molecular arrangement based on π–π stacking interactions (3.399 Å); this causes the new material to have a higher hole mobility than the standard IDTC4-based HTM. Moreover, the photoluminescence quenching in a perovskite/HTM film structure was shown to be more effective at the perovskite/IDTC6-TPA interface than at the perovskite/IDTC4-TPA interface. Consequently, devices fabricated using IDTC6-TPA show superior photovoltaic properties (exhibiting an optimal performance of 15.43%) compared with IDTC4-TPA-containing devices. [ABSTRACT FROM AUTHOR]

Sulfoxides and cyclic ureas are photochemically deoxygenating solvents in which the oxidative stress could be released and efficient triplet–triplet annihilation photon upconversion (TTA-UC) can operate in air. Such solvents can be practically screened out by harnessing the property of photo-activated phosphorescence. [ABSTRACT FROM AUTHOR]

It is always essential for the design and optimization of devices to discover the interaction mechanism of light with hybrid perovskite materials in air. However, the mechanism is currently still under debate, although there is already a consensus that oxygen gas molecules along with light irradiation contribute predominantly to photoluminescence (PL) enhancements in perovskite crystals. In this work, we measured the light intensity, excitation energy, oxygen environment and depth dependence of the photoluminescence (PL) enhancements in perovskite single crystals by using confocal fluorescence microscopy. The dependence of the PL enhancement on the excitation energy and environment explicitly indicates the indispensable roles of photon-generated carriers and oxygen gas molecules. Moreover, the PL enhancement depth of over 100 μm in an oxygen environment demonstrates that the penetration of oxygen species must be the dominant mechanism, rather than their diffusion. Furthermore, the passivation of the oxygen species occurs in a stable and long-term manner, even in the absence of light, in contrast to that of carriers and neutral species. On the basis of these solid data, we propose that the O2− superoxides yielded from the reaction of O2 with free-moving electrons are responsible for the related PL enhancement effect involved in our work and other literature reports. This paper will definitely deepen our understanding of the interaction mechanism in this field. [ABSTRACT FROM AUTHOR]