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Ferroelectric coupling effects on the energy-band structure of hybrid heterojunctions are investigated using hybrid photovoltaic devices with poly(3-hexylthiophene-2,5-diyl) (P3HT)/ZnO and poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)). The self-organized P(VDF-TrFE):P3HT photoactive layer forms a novel architecture consisting of P3HT domains in a P(VDF-TrFE) matrix. The energy-band structure at the interface of the p-n heterojunction is tuned by artificial control of the ferroelectric polarization of the P(VDF-TrFE) material, consequently modulating the photovoltaic performance of the hybrid photovoltaic devices.

ABSTRACT:We investigated the influence of the Ga doping in the ZnO interlayer as an electron transport layer (ZnO ETL) on the nanoscale phase separation in the bulk heterjunction (BHJ) layer coated on the ETL as well as the morphological and electrical properties of a low temperature sol−gel-derived pristine ZnO ETL (P-ETL) and Ga-doped ZnO ETL (G-ETL), which affect the performance of inverted organic solar cells (IOSCs). X-ray photoelectron spectroscopy (XPS) confirms the successful incorporation of the element Ga in the ZnO ETL. The short circuit current densities (J SC ) of IOSCs fabricated using a G-ETL were significantly improved from those of IOSCs fabricated with a P-ETL. The maximum J SC was obtained at 2 at. % Ga doping. The IOSCs fabricated with a 2 at. % G-ETL demonstrated power conversion efficiencies of 3.51% (P3HT:PC 60 BM) and 5.43% (PCDTBT:PC 70 BM), which were higher than the power conversion efficiencies of 2.88% (P3HT:PC 60 BM) and 4.90% (PCDTBT:PC 70 BM) of the IOSCs fabricated with a P-ETL under simulated air mass 1.5 global full-sun illumination. The better performance was attributed to the improved electrical properties of the G-ETL and the enhanced nanoscale phase separation in the BHJ active layer.

Wurtzite nanomaterials, such as ZnO, GaN, and InN, have become a subject of great scientific and technological interest as they simultaneously have piezoelectric and semiconductor properties. In particular, the piezoelectric potential (piezopotential) created by dynamic straining in the nanowires drives a transient flow of current in the external load, converting mechanical energy into electricity. Further, the piezopotential can be used to control the carrier generation, transport, separation, and/or recombination at the metalsemiconductor junction or p-n junction, which is called the piezophototronic effect. This paper reviews the recent advances on the piezophototronic effect to better use the piezophototronic effect to control the carrier generation, transport, separation and/or recombination for improving the performance of optoelectronic devices, such as photon detectors, solar cells and LEDs. This paper also discusses several research and design studies that have improved the output performance of optoelectronic devices.