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The purpose of this paper is to develop a computational model for the simulation of heterojunction organic photovoltaic devices with a specific application to a light harvesting capacitor (LHC) consisting of a double layer of organic materials connected in series with two insulating layers and an external resistive load.

The model is based on a coupled system of nonlinear partial and ordinary differential equations describing current flow throughout the external resistive load as the result of exciton generation in the bulk, exciton dissociation into bonded pairs at the acceptor-donor material interface, and electron/hole charge generation and drift-diffusion transport in the two device materials.

Numerical simulation results are shown to be in good agreement with measured on-off transient currents and allow for novel insight on the microscopical phenomena which affect the external LHC performance, in particular, the widely different time scales at which such phenomena occur and their relation to the overall device dynamics.

The LHC demonstrates the viability of a novel approach for converting light energy into an electric current without a steady state flow of free charge carriers through the semiconducting layers. The new insight about the microscopic working principles that determine the macroscopically observed behavior of the LHC obtained via the model proposed in this paper are expected to serve as a basis for studying techniques for exploiting the full potential of the LHC.

The latest information from the magazine chemist is extremely valuable. He has dealt with milk‐adulteration and how it is done. His advice, if followed, might, however, speedily bring the manipulating dealer before a magistrate, since the learned writer's recipe is to take a milk having a specific gravity of 1030, and skim it until the gravity is raised to 1036; then add 20 per cent. of water, so that the gravity may be reduced to 1030, and the thing is done. The advice to serve as “fresh from the cow,” preferably in a well‐battered milk‐measure, might perhaps have been added to this analytical gem.

There are very few individuals who have studied the question of weights and measures who do not most strongly favour the decimal system. The disadvantages of the weights and measures at present in use in the United Kingdom are indeed manifold. At the very commencement of life the schoolboy is expected to commit to memory the conglomerate mass of facts and figures which he usually refers to as “Tables,” and in this way the greater part of twelve months is absorbed. And when he has so learned them, what is the result? Immediately he leaves school he forgets the whole of them, unless he happens to enter a business‐house in which some of them are still in use; and it ought to be plain that the case would be very different were all our weights and measures divided or multiplied decimally. Instead of wasting twelve months, the pupil would almost be taught to understand the decimal system in two or three lessons, and so simple is the explanation that he would never be likely to forget it. There is perhaps no more interesting, ingenious and useful example of the decimal system than that in use in France. There the standard of length is the metre, the standard of capacity the cubic decimetre or the litre, while one cubic centimetre of distilled water weighs exactly one gramme, the standard of weight. Thus the measures of length, capacity and weight are most closely and usefully related. In the present English system there is absolutely no relationship between these weights and measures. Frequently a weight or measure bearing the same name has a different value for different bodies. Take, for instance, the stone; for dead meat its value is 8 pounds, for live meat 14 pounds; and other instances will occur to anyone who happens to remember his “Tables.” How much simpler for the business man to reckon in multiples of ten for everything than in the present confusing jumble. Mental arithmetic in matters of buying and selling would become much easier, undoubtedly more accurate, and the possibility of petty fraud be far more remote, because even the most dense could rapidly calculate by using the decimal system.