Perovskite solar cells have emerged as the next-generation high-efficiency solar cell, but their absorption is mostly limited to the visible (vis) range. One possible solution is to integrate near-infrared (NIR)-to-vis photon upconversion (UC). Herein, we show the first example of endowing perovskite solar cells with NIR sensitivity by using solid films showing NIR-to-vis UC based on triplet-triplet annihilation (TTA). A high TTA-UC efficiency of 4.1 � 0.3 % at an excitation intensity of 125 W/cm 2 is achieved by sensitizing a rubrene (acceptor) triplet with an osmium (Os) complex donor having singlet-to-triplet (SÀ T) absorption in the NIR range, and by increasing the fluorescence quantum yield through energy harvesting to a highly fluorescent collector. In particular, our spectroscopic studies indicate that the upconverted acceptor singlet energy is almost selectively transferred to the collector rather than being quenched by the donor. By attaching the TTA-UC film behind a semi-transparent perovskite solar cell, a photocurrent generation is observed under excitation at 938 nm.

The present research reports on the effect of initial mixture temperature on the experimentally measured detonation cell size for hydrogen-air-steam mixtures. Experimental and theoretical research related to combustion phenomena in hydrogen-air-steam mixtures has been ongoing for many years. However, detonation cell size data currently exists for hydrogen-air-steam mixtures up to a temperature of only 400K. Severe accident scenarios have been identified for light water reactors (LWRs) where hydrogen-air mixture temperatures in excess of 400K could be generated within containment. The experiments in this report focus on extending the cell size data base for initial mixture temperatures in excess of 400K. The experiments were carried out in a 10-cm inner-diameter, 6.1-m long heated detonation tube with a maximum operating temperature of 700K and spatial temperature uniformity of _14K. Detonation cell size measurements provide clear evidence that the effect of hydrogen-air initial gas mixture temperature, in the range 300K-650K, is to decrease cell size and, hence, to increase the sensitivity of the mixture to undergo detonations. The effect of steam content, at any given temperature, is to increase the cell size and, thereby, to decrease the sensitivity of stoichiometric hydrogen-air mixtures. The hydrogen-air detonability limits for the 10-cm inside-diameter test vessel, based upon the onset of single-head spin, decreased from 15 percent hydrogen at 300K down to about 9 percent hydrogen at 650K. The one-dimensional ZND model does a very good job at predicting the overall trends in the cell size data over the range of hydrogen-air-steam mixture compositions and temperature studied in the experiments.

Triplet‐triplet annihilation‐based photon upconversion (TTA‐UC) of near‐infrared (NIR) light to visible light in the solid‐state remains as a great challenge due to the sensitizer aggregation that impedes the efficient triplet energy transfer. Herein, we successfully introduce a molecular sensitizer exhibiting direct singlet‐to‐triplet (S–T) absorption into a new emitter‐based metal‐organic framework (MOF) to achieve an efficient triplet sensitization and a NIR‐to‐visible TTA‐UC in the solid‐state.

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