Study On Enhancing Light Absorption Of Polymer-based Organic Thin Film Solar Cells By Employing Micro-nano Structure

Organic thin film solar cells(OSCs)have attracted a lot of attention from researchers,because of their advantages such as thinness,low cost,and flexibility.However,the power conversion efficiency(PCE)of organic thin film solar cells is still low,which greatly limits its development.Therefore,how to improve the PCE of OSCs has become the focus of researchers.Through appropriate structural design,the micro-nano structures with various patterns are introduced into the OSCs,which can effectively enhance the light absorption of the OSCs.The main research contents of this paper are mainly divided into the following three aspects: 1.Preparation and characterization of multi-morphological multi-period micro-nano composite structuresIn this work,the micro-nano structures with adjustable morphology and adjustable period are prepared by combining traditional lithography and two-beam interference lithography.For traditional lithography,SU-8 negative photoresist is chosen in this work.By designing masks with different morphologies,micro-structures of various shapes such as strips,rectangular lattices,circular lattices and hexagonal lattices were prepared,thus realizing the preparation of different morphological microstructures;For the laser two-beam interference technique,we prepared the sinusoidal grating structures with a period of 2 μm and 350 nm by adjusting the angles of the two coherent beams,thus realizing the preparation of microstructures with different periods;By combining the two lithography techniques,we have prepared micro-nano structures with adjustable morphology and period by successive two exposures,thus realizing the preparation of multi-morphological multi-period micro-nano composite structures.2.Micron grating structure improves the PCE of OSCsStrip grating structures with a period of 6 μm by conventional photolithography technology are prepared.By controlling the dilution ratio of photoresist to acetone,the grating structures with different heights are obtained.The micro-grating structures with different heights are empolyed into OSCs.Compared with the planar device,the light absorption efficiency of the grating device is improves significantly.Due to the scattering effect,which effectively improves the PCE of the OPV.At the same time,as the height of the grating increases,the PCE is increased.Compared with the planar device,the PCE of the grating device with the dilution ratio of photoresist and acetone of 1:4 was sequentially increased by 9.59 %.The PCE of the grating-based device with photoresist:acetone = 1:2 was increased by 19.18%.The PCE of the grating-based device with photoresist:acetone = 1:0 is increased by 28.77%.3.Study on enhancement of light absorption efficiency of surface plasma-micro cavity excited to top-orange organic thin film solar cellsThrough appropriate design,periodic rectangular grating structure is empolyed into TOSCs.The rigorous coupled wave analysis(RCWA)algorithm and the finite time domain difference(FDTD)algorithm are used to analyze the TOSCs ideal model with grating structure,and analyze the coupling between the surface plasmon(SPPs)mode and microcavity mode in TOSCs.By adjusting the size of the grating period and the thickness of the active layer,the composite SPPs mode,the microcavity mode and the three regions of the intrinsic absorption of the active layer material coincide.Since the composite SPPs mode and the microcavity mode form an anti-cross coupling,the effect becomes surface plasmon-microcavity.The enhancement of the surface plasmon-microcavity local field effectively improves the light absorption efficiency of the active layer in TOSCs.By calculation,the light absorption efficiency in the wavelength range of 470 to 600 nm is improved by nearly 19%.