Protonation and ring closure of stereoisomeric alpha-substituted cinnamic acids in superacidic media studied by 13C NMR spectroscopy and computations

Five alpha-substituted cinnamic acids [(E)- and (Z)-2,3-diphenyl-, (E)- and (Z)-3-(2-methoxyphenyl)-2-phenyl- and (E)-2-(2-methoxyphenyl)-3-phenyl-propenoic acids] have been protonated in fluorosulfonic acid at -78 degrees C, Protonation of the carboxylic group and a second protonation on the methoxy group at -78 degrees C or the ring bearing the methoxy group at 0 degrees C have been observed by C-13 NMR spectroscopy Upon protonation (Z)-alpha-phenylcinnamic acid is transformed to a protonated indenol derivative, Dehydrative ring closure begins at -78 degrees C and goes to completion at 0 degrees C, Similar transformations of the other studied Z-acid are suppressed by the deactivating effect of the protonated methoxy group. Only protonation has been observed for the E-acids at -78 degrees C as well as 0 degrees C, Calculations at the HF/3-21G level provide the equilibrium structures of the corresponding cations, Results of IGLO/C-13 NMR shift calculations are in good agreement with the experimental findings

Development of high efficiency (14 percent) solar cell array module

Most effort was concentrated on development of procedures to provide large area (3 in. diameter) high efficiency (16.5 percent AM1, 28 C) P+NN+ solar cells. Intensive tests with 3 in. slices gave consistently lower efficiency (13.5 percent). The problems were identified as incomplete formation of and optimum back surface field (BSF), and interaction of the BSF process and the shallow P+ junction. The problem was shown not to be caused by reduced quality of silicon near the edges of the larger slices

Development of High Efficiency (14%) Solar Cell Array Module

High efficiency solar cells required for the low cost modules was developed. The production tooling for the manufacture of the cells and modules was designed. The tooling consisted of: (1) back contact soldering machine; (2) vacuum pickup; (3) antireflective coating tooling; and (4) test fixture