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Organic–inorganic hybrid perovskites play an important role in improving the efficiency of solid-state dye-sensitized solar cells. In this paper, we systematically explore the efficiency-enhancing mechanism of ABX3 (A = CH3NH3; B = Sn, Pb; X = Cl, Br, I) and provide the best absorber among ABX3 when the organic framework A is CH3NH3 by first-principles calculations. The results reveal that the valence band maximum (VBM) of the ABX3 is mainly composed of anion X p states and that conduction band minimum (CBM) of the ABX3 is primarily composed of cation B p states. The bandgap of the ABX3 decreases and the absorptive capacities of different wavelengths of light expand when reducing the size of the organic framework A, changing the B atom from Pb to Sn, and changing the X atom from Cl to Br to I. Finally, based on our calculations, it is discovered that CH3NH3SnI3 has the best optical properties and its light-adsorption range is the widest among all the ABX3 compounds when A is CH3NH3. All these results indicate that the electronegativity difference between X and B plays a fundamental role in changing the energy gap and optical properties among ABX3 compounds when A remains the same and that CH3NH3SnI3 is a promising perovskite absorber in the high efficiency solar batteries among all the CH3NH3BX3 compounds. [ABSTRACT FROM AUTHOR]

We questioned 75 patients after inpatient oral and maxillofacial operations to find out how satisfied they were with the extent to which their pain had been controlled. Seventy (93%) had had postoperative pain. In 33 (47%), it was moderate and in 24 (34%), severe. Analgesic drugs were not given immediately to 6 of the 24 patients who requested them. Seventeen (24%) reported that the pain was worse than they had expected, but 74 of the 75 patients were satisfied with the pain control they received. We conclude that patients' expectations of pain control are low and that questions about satisfaction should not be used in isolation., (Copyright 2000 The British Association of Oral and Maxillofacial Surgeons.)