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We investigate polymer bilayer structures that can be utilized effectively for efficient photovoltaic properties. The transport characteristics of photogenerated free charge carriers across the interface of a bilayer consisting of p-type polymer poly(3-octyl thiophene) (P3OT) or poly(2-methoxy, 5-(2-ethylhexoxy)-1, 4-phenylene vinylene) (MEHPPV) and n-type polymer poly(benzamidazobenzo phenanthroline) (BBL) are studied using photocurrent spectral response, intensity modulated photocurrent spectra, current-voltage, and thermally stimulated current measurements. The parameters governing the device efficiency are controlled by the interfacial defect characteristics and electric field redistribution in the device. A clear evidence of these defect states at the polymer–polymer interface is revealed using the time and frequency domain photocurrent measurements. We compare the figure of merits of the P3OT/BBL and MEHPPV/BBL structures and correlate these properties to the interfacial processes.

Packaging of organic photovoltaic (OPV) devices is an important issue which has been rarely addressed in the past. With the recent reports of high efficiency organic photovoltaics (6%), the need to produce materials which can effectively protect the device from degradation due to exposure to oxygen, moisture and radiation is pressing. We report a novel Saran (a co-polymer of vinylidene chloride and acrylonitrile) based polymer nanotube composite, which shows high transparency in the visible region, good barrier properties and thermal stability, for use as an encapsulant for OPV devices. Different loadings of Saran and boron nitride nanotubes were taken and the composites were prepared to optimize the composition of the composite. UV-visible spectroscopy, infra-red spectroscopy and thermal analysis were used to characterize the composite. The barrier properties of the composite were tested on poly(3-hexylthiophene), which is used in high efficiency OPV devices.

Dual properties of photoconduction and electroluminescence (EL) in hybrid devices consisting of a nanocluster semiconductor layer and a polymer are reported. It is observed that the photocurrent spectral response and efficiency in these multilayer devices are similar to that of the semiconductor component, while the EL spectral responses are closer to that of the polymer layer. The results are confirmed using the nanoparticle semiconductor, cadmium sulphide CdS, of different particle sizes and polymers representing a wide spectral range. A general feature of efficient photocurrent spectral response corresponding to nanoparticle and an appreciable EL response corresponding more to the active polymer are observed in all devices and results in wide, separated spectral windows. Current–voltage responses also indicate possibilities of added tunability in these devices.

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