Piezo-photovoltaic coupling in CdS-based thin-film photovoltaics

Abstract

We report a summary of our recent study of piezo-and pyroelectricity in CdS-based photovoltaics including CdTe and CuIn͑Ga͒Se 2 absorber devices. The strong pyro-and piezo-effects in CdS significantly affect the electric field distribution and the physics of device operations. We introduce the concept of pyro-photovoltaic coupling where the photovoltaic effect and the CdS polarization strongly depend on each other. Our quantitative modeling shows that the CdS polarization turns out to be beneficial for photovoltaic technology, making it more forgiving. Three experimental setups utilized in our work were aimed at exerting mechanical stresses corresponding to the device squeezing, bending, and flexing; we used the substrate, superstrate, and flexible substrate structures. Our understanding points at previously unexplored venues in thin-film photovoltaic technology.

Increasing bulk photovoltaic current by strain tuning

“…This coupling between piezoelectricity and semiconductor properties is known as the “piezotronic” effect or, when photoexcited electrons are added to the picture, the piezophototronic effect ( 17 , 26 ). This interplay between piezoelectric and PV properties has been described before ( 27 , 28 ). However, in the present case, the measurements did not show a systematic dependence on the electrode material, which should be expected if the effect was based on a variation of Schottky barrier height.…”

Towards understanding junction degradation in cadmium telluride solar cells

“…In addition to specific mechanisms, one can study the effects of alternative band structures such as a light-modulated front barrier 49 or a gull-wing singularity due to the piezoelectric nature of CdS. 50 The latter may be particularly applicable because it naturally provides defect generation in the narrow band of the field singularity at the junction (where nonequilibrium electrons accumulate). Alternative charge transport mechanisms, such as optimum channel hopping, 51 may also have important effects and can be investigated with this simulation tool.…”

Piezoelectric nanogenerator using CdS nanowires

“…The low voltage output is likely to be resulted from the phase transition between ZB and WZ phases along the growth direction of the NW, because WZ phase is piezoactive, while ZB phase is not. 14 The presence of the ZB phase along the growth direction is disadvantageous to the piezoelectronic performance of the CdS NWs.…”