Flexible Substrates With Viewing Angle Independent Colors And Their Applications In Organic Solar Cells

Colourful organic solar cells(OSCs)can meet the aesthetic needs of building-integrated photovoltaics(BIPV)and wearable devices.The current colorization schemes for OSCs can be divided into two categories:pigment colour schemes and structural colour schemes.The limitations of pigment colour schemes are that the colours available are limited and have a serious impact on device performance.Structural colour schemes produce angle-dependent colours.To address these issues.this work proposes a structural color scheme using silicon dioxide microsphere(SiO2 NP)arrays with viewing independent colours.In this paper,we first develop substrates with amorphous photonic crystals(APCs)structure.By adjusting the size of the SiO2 NPs,colorful structures with continuously tunable viewing-angle independent olours from blue to red was obtained.By combining APCs substrates with rigid devices,the OSCs with Janus colorful effect are achieved through the synergistic effect of the active layer and the translucent electrode.On the side of the substrate,the devices show adjustable reflection colour affected by APCs,but with blue transmission not affected by APCs,and the colourful devices also achieve impressive device performance.By combining APC with polyimide(PI),flexible OSCs with viewing-angle independent structural colour were obtained.Although the APC scheme achieves viewing-angle independent colourful flexible OSCs,the PI stripping process is complex.Therefore,we further develops a one-step moulding processed spherical photonic crystal(SPC)scheme.The SiO2 NP dispersion is mixed into Polydimethylsiloxane(PDMS)to obtain spherical droplets,which are used as a template for assembly,so that the SiO2 NP self-assembles into SPCs during the low-temperature heating and curing of PDMS to obtain PDMS substrates with viewing-angle independent structural colours.At the same time,tunable reflection colours were achieved by assembling SiO2 NPs of different sizes.Based on this,flexible OSCs based on a transparent front electrode of silver nanowires and a translucent silver film back electrode was prepared,which also achieve Janus colorful effect,while maintaining the device with a considerable efficiency.