Study On Hybrid Solar Cells Based On One-dimensional ZnO Nanomaterial Arrays

In this paper, well aligned one-dimensional ZnO nanotube arrays and nanorode arrayswere fabricated on ITO substrate by two-step electrochemical method and hydrothermalmethod, respectively. A suitable thickness of CdTe nanodendrite was electrodeposited onZnO nanotube array, and a CdTe@ZnO nanotube array shell-core structure was obtained.Then a thin P3HT layer was spin-coated onto the CdTe@ZnO nanotube array shell-corestructure, and a three-component P3HT@CdTe@ZnO composite film was obtained. Asuitable thickness of CdSe nanoparticle was electrodeposited on ZnO nanorode array, anda CdSe@ZnO nanorode array shell-core structure was obtained. And then a thin P3HTlayer or PCPDTBT layer was spin-coated onto the CdSe@ZnO nanorode array shell-corestructure, and a three-component P3HT@CdSe@ZnO or PCPDTBT@CdSe@ZnOcomposite film was obtained, subsequently a hole transporting layer of PEDOT:PSS wasspin-coated onto the three-component composite film. The composition、morphology andstructure of electrode materials were determined and analyzed by means of SEM、XRD、HRTEM、EDS and UV-visible absorption spectrum. Photovoltaic properties of solar cellsbased on different electrode materials were also studied.Electrodes such as ZnO nanotube、 CdTe@ZnO and P3HT@CdTe@ZnO wereassembled respectively with platinized FTO counter electrodes to fabricate different kindsof semiconductor-sensitized solar cells. Studies showed that a hexagonal wurtzite structureof ZnO with a wall thickness of50nm and an inner diameter of200nm and a zinc blendestructure of CdTe with a lattice spacing of0.37nm were preparaed. Different CdTenanodendrite shell thickness could be obtained by adjusting the total charge quantityapplied during deposition, and the best deposition charge was1.5C. CdTe nanocrystallinehas a good light absorption capability and has broadened the absorption spectra of ZnO to840nm. The solar cell based on the CdTe(1.5C)@ZnO electrode displayed the bestphotovoltaic property among devices based on CdTe(0.5C、1.0C、1.5C、2.0C)@ZnOelectrodes, and its power conversion efficiency reached1.0%. When P3HT wasspin-coated onto CdTe@ZnO electrode, photovoltaic properties of solar cells based onP3HT@CdTe(1.5C)@ZnO electrode was improved greatly. The energy conversionefficiency of the solar cell based on the P3HT@CdTe(1.5C)@ZnO electrode reached1.38%, which was the highest among all the devices. The significant improvement on photovoltaic property was attributed to the p-n heterojunction which was formed betweenthe interface of CdTe and P3HT. The p-n heterojunction could facilitate the transportationand separation of photogenerated charge.Electrodes such as P3HT@ZnO、P3HT@CdSe(﹣0.6V、﹣0.8V、﹣1.0V)@ZnO、PCPDTBT@ZnO、PCPDTBT@CdSe(﹣0.6V、﹣0.8V、﹣1.0V)@ZnO were assembledrespectively with gold-plated copper to fabricate different kinds of organic-inorganichybrid solar cells. Studies showed that a hexagonal wurtzite structure of ZnO waspreparaed by hydrothermal method and different diameters could be obtained by changedthe reaction solution concentration, the best condition was0.05M solution of Zn (NO3)2and HTM. A wurtzite structure of CdSe was preparaed, different nanoparticle sizes ofCdSe could be obtained by adjusting the deposition voltage, and a suitable shell thicknesswith uniform CdSe nanoparticle of20nm was obtained when the deposition voltage was﹣1.0V. CdSe nanocrystalline has a good light absorption capability and has broadenedthe absorption spectra of ZnO above to700nm. The hybrid solar cells based on theP3HT@CdSe(﹣1.0V)@ZnO and PCPDTBT@CdSe(﹣1.0V)@ZnO electrodesdisplayed the best photovoltaic property among devices based on the above electrodeswith power conversion efficiency0.48%and0.50%, respectively. The significantimprovement on photovoltaic property was attributed to the p-n heterojunction which wasformed between the interface of CdSe and P3HT or CdSe and PCPDTBT. The p-nheterojunction could facilitate the transportation and separation of photogenerated charge.