Abstract: Polyvinylidene fluoride (PVDF) films and co-polymers thereof possess the highest values of piezoelectric and pyroelectric constants of any known polymer. These films, up to present, have been first subjected to stretching and then to a high electric field (or corona charge) at an elevated temperature to provide a maximum piezoelectric constants (d.sub.31) of about 30-35 pC/N and a maximum pyroelectric constants (p) of about 3.5 nC/cm.sup.2 K. It has now been found that the piezoelectric constant d.sub.31 and pyroelectric constant p of these films can be increased up to about 60 pC/N and 6 nC/cm.sup.2 K respectively when they are subjected to simultaneously stretching and corona poling with a poling field E.sub.p =0.55MV/cm, a stretching ratio S.R.=4.5X and a poling temperature T.sub.p =80.degree. C.

Abstract: An induced junction solar cell includes a silicon semiconductor wafer with an aluminum ohmic contact layer on one surface, a thin oxide layer on the other surface, a grid-type aluminum contact on the oxide layer and an electret, i.e. charged outer polymer layer covering the grid-type contact and exposed oxide layer. The electric field of trapped charges in the electret penetrate the semiconductor and separate photogenerated carriers. Minority carriers are extracted through a rectifying grid-type contact to permit a build-up of potential and a barrier for majority carriers.