Characterizations of some materials used in the third generation solar cells

Abstract

The materials for the third generation thin film solar cells range from inorganic, metal-organic to organic materials. We choose the typical ones for research. Cu₂ZnSnS₄ (CZTS) thin film solar cells for inorganic ones, perovskite is the typical hybrid metal-organic material for solar cells, and polymer:fullerene blends is effective composite for high efficiency polymer solar cells. Temperature-dependent Quantum Efficiency (QE) spectra and wavelength-dependent current-voltage (I-V) curves for selenium-free CZTS thin film solar cells are measured. The experimental results show that there exist many defects in the interface of buffer layer and absorption layer, and the defects intra and inter layers lead a drop in the open-circuit voltage (V_OC). A relative thicker absorption layer is good for the absorption of longer wavelength light, while increasing the transmission of shorter wavelength light enhances its light-to-electricity conversion efficiency. Due to the good photoluminescent property, nanostructured perovskite nanowires (NWs) are used in the application for image sensors and LEDs. For the MAPbBr₃ perovskite NWs dedicated for image sensors, the carrier lifetime of 14.3 ns makes it the promising material for the application. As for the MAPbCl₃ NWs used for LEDs, NWs with a larger diameter show stronger PL intensity and possess longer carrier lifetime. For the PffBT4T-2OD:PC₇₁BM blends, ITO/blends/Al sandwich structure devices are annealed at different temperatures. We obtain the exciton diffusion lengths from the biased voltage dependent photocurrent spectra of the sandwich structure devices and find that there is no obvious difference among different temperature annealed samples. It shows that the higher annealing temperature which enhances the efficiency of the solar devices does not result in the obvious exciton diffusion length change of the blends, so the enhancement of efficiency is not due to the enhanced exciton diffusion length.

Date of Award	2016
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology