Design And Performance Of Composite Light Management Structures For Organic Solar Cells

Nowadays,human society is developing at a high speed.Energy and environment problems are becoming more and more prominent.To help achieve the double carbon targets,the green transformation of energy has been the general trend.Among them,solar energy has become a hotspot for research owing to its wide coverage,small regional restrictions,and environmental friendliness.Energy conversion devices,as the conversion of solar energy and other types of energy,the importance of their research is self-evident.Among them,organic solar cells with low manufacturing cost,simple process,good flexibility,large-scale roll-to-roll production,and other advantages have attracted much attention.At present,the photovoltaic conversion efficiency（PCE）of single-junction organic solar cells has exceeded 18%.However,due to the short exciton diffusion length and low carrier transport efficiency,the thickness of the active layer is limited to an extremely thin range,and thus the light absorption ability is weak.To solve the above problems,this research improves the light absorption ability of organic solar cells by designing the composite light management structure to confine more light into the photoactive layer.The main research is as follows:（1）Based on the ITO/PEDOT:PSS/P3HT:PC₆₁BM/ZnO/Al normal device structure,the composite light management structure of ITO nanocylinder arrays on the front surface and Al nanosquare arrays on the back surface was designed to synergistically enhance the light trapping ability of the photoactive layer.The effects of different diameter-to-period ratios（D/P）and heights（H₁）of ITO nanocylinders and the edge lengths（L）of Al square arrays on the optical performance of organic solar cells were investigated.The results show that the device performance is optimized when the ITO nanocylinder parameters P=300 nm,D/P=0.667,H₁=80 nm,and L=220 nm.The short-circuit current density(J_sc)is 12.47 m A/cm~2,which is 36.58%higher than that of 9.13 m A/cm~2delivered by the planar control device.Electrical calculations also show that the PCE of the device with the introduction of the composite light management structure can be enhanced by 38.52%,from 5.40%to7.48%.In addition,oblique incidence data demonstrates that the device with introducing the composite light management structure exhibits excellent omnidirectional light trapping ability.Moreover,light absorption is still significantly improved under other two different photoactive-layer systems,PTB7:PC₇₁BM and PBDB-T:ITIC,which verifies the universality of the proposed composite light management structure for various photoactive-layer systems of organic solar cells.（2）Based on the ITO/ZnO/PTB7:PC₇₁BM/MoO₃/Ag inverted normal device structure,the composite light management structure with ITO hemisphere arrays on the front surface and Ag nanodisk particles embedded inside the photoactive layer was designed.The effects of different radii（R）of the ITO hemisphere and periods（P）,heights（H）and diameters（D）of Ag nanodisk particles on the optical performance of the organic solar cell were investigated.The results show that the device performance is optimized when the parameters of ITO hemisphere arrays R=140 nm and the Ag nanodisk particles P=300 nm,H=30 nm,D=160 nm.Light absorption is enhanced in different degrees in the ultra-wide wavelength range of 300-800 nm.The J_scis19.67 m A/cm~2,which is 43.58%higher than that of 13.70 m A/cm~2delivered by the planar control device.Electrical calculations also show that the PCE of the device with the introduction of the composite light management structure can be enhanced by46.57%,from 6.80%to 9.96%.Simulation results also show the improvement of light absorption in the photoactive layer when Ag nanodisk particles are embedded in different positions.In addition,oblique incidence data shows that the device exhibits excellent omnidirectional light trapping ability,which is feasible for practical applications.（3）On the basis of the above work,breaking the traditional structure of electrodes for organic solar cells,the composite light management structure of interdigitated back contact Ag nanograting electrodes inside the photoactive layer and PMMA nano-half-cylinder arrays on front surface was designed.The effects of periods（P）,widths（W）and heights（H）of Ag nanograting electrodes,thicknesses（T）of the planar PMMA layers and different radii（R）of PMMA nano-half-cylinders on the optical performance of organic solar cells were investigated.The results show that the optimal light absorption improvement of the photoactive layer is achieved when R=100 nm,P=300 nm,H=100 nm,T=100 nm,W=120 nm,and the J_scis 18.81m A/cm~2,which is 40.69%higher than that of 13.37 m A/cm~2delivered by the planar control device.Electrical calculations show that the PCE of the device with the composite light management structure is improved by 43.07%compared with the control device.Similarly,the oblique incidence conditions are investigated and the results show that the device has an excellent light management ability in a broad angle range.