Nanoporous submicron TiO 2 spheres of diameters around 200 nm are synthesized by a hydrothermal process and used as a scaffold layer for improving light absorption, charge transportation, as well as photovoltaic performance in holetransport-layer free perovskite solar cells employing carbon counter electrodes. The TiO 2 submicron spheres show a porous feature with high specific surface area, which is essential for perovskite infiltration, charge extraction, and transportation in mesoscopic perovskite solar cells. Furthermore, big spheres exhibit better light scattering property compared to traditional TiO 2 nanoparticles, thus enhancing light absorption in corresponding devices. The present perovskite solar cells employ a TiO 2 scaffold layer of optimized thickness of about 600 nm and show an average power conversion efficiency of 13.46 ± 0.41%, which is 18.4% higher than that of counterparts based on TiO 2 nanoparticle (11.37 ± 0.40%). The champion cell exhibits an impressive efficiency of 14.3%, which is very competitive in perovskite solar cells without a hole transport layer using a carbon electrode. Moreover, our carbon based perovskite solar cell shows excellent long-term stability against moisture and heat with negligible degradation for 210 days of storage under ambient conditions. KEYWORDS: TiO 2 nanoporous sphere, HTM-free perovskite solar cells, TiO 2 scaffold layer, CH 3 NH 3 PbI 3 , carbon counter electrodes, long-term stability

The construction of silicone elastomers crosslinked by a natural crosslinker under a catalyst-free method is highly desirable. Herein we present catalyst-free silicone elastomers (SEs) by simply introducing tannic acid (TA) as a natural crosslinker when using poly (aminopropylmethylsiloxane-co-dimethylsiloxane) (PAPMS) as the base polymer. The crosslinked bonding of these SEs can be easily changed from hydrogen bonding to covalent bonding by altering the curing reaction from room temperature to heating condition. The formability and mechanical properties of the SEs can be tuned by altering various factors, including processing technique, the amount of TA and aminopropyl-terminated polydimethylsiloxane, the molecular weight and -NH2 content of PAPMS, and the amount of reinforcing filler. The hydrogen bonding was proved by the reversible crosslinking of the elastomers, which can be gradually dissolved in tetrahydrofuran and re-formed after removing the solvent. The covalent bonding was proved by a model reaction of catechol and n-decylamine and occurred through a combination of hydroxylamine reaction and Michael addition reaction. These elastomers exhibit good thermal stability and excellent hydrophobic property and can bond iron sheets to hold the weight of 500 g, indicating their promising as adhesives. These results reveal that TA as a natural product is a suitable “green” crosslinker for the construction of catalyst-free silicone elastomers by a simple crosslinking strategy. Under this strategy, TA and more natural polyphenols could be certainly utilized as crosslinkers to fabricate more organic elastomers by selecting amine-containing polymers and further explore their extensive applications in adhesives, sealants, insulators, sensors, and so forth.

In this work, we have demonstrated a facile approach to synthesize donut-shaped LiMn2O4 comprising interpenetrating nanograins, and this material demonstrates excellent high-rate cycling reversibility.

Cs containing triple cation HTM-free carbon based PSCs were fabricated out of a glovebox showing the best performance over 15%.

No abstract