We present a systematic experimental study on the impact of disorder in advanced nanophotonic light-trapping concepts of thin-film solar cells. Thin-film solar cells made of hydrogenated amorphous silicon were prepared on imprint-textured glass superstrates. For periodically textured superstrates of periods below 500nm, the nanophotonic light-trapping effect is already superior to state-of-the-art randomly textured front contacts. The nanophotonic light-trapping effect can be associated to light coupling to leaky waveguide modes causing resonances in the external quantum efficiency of only a few nanometer widths for wavelengths longer than 500nm. With increasing disorder of the nanotextured front contact, these resonances broaden and their relative altitude decreases. Moreover, overall the external quantum efficiency, i.e., the light-trapping effect, increases incrementally with increasing disorder. Thereby, our study is a systematic experimental proof that disorder is conceptually an advantage for nanophotonic light-trapping concepts employing grating couplers in thin-film solar cells. The result is relevant for the large field of research on nanophotonic light trapping in thin-film solar cells which currently investigates and prototypes a number of new concepts including disordered periodic and quasi periodic textures

This work demonstrates a performance improvement of state‐of‐the‐art silicon solar cells by cloaking their metal contact fingers. The cloaking free‐form surfaces are fabricated on silicon heterojunction solar cells using direct laser writing of polymers and subsequent soft imprinting. Cloaking performance is determined experimentally by measuring spatially resolved and angle‐resolved current generation and the spectral response of the cell. The short‐circuit current density of the cell increases by 7.3%; its power‐conversion efficiency is enhanced by 9.3%. Overcompensation of the shadowing loss is found to be caused by improved light‐gathering and light‐trapping in the polymer layer. The experimental findings are in good agreement to ray‐tracing simulations.

In this work, we have improved the absorption properties of thin film solar cells by introducing light trapping reflectors deposited onto self-assembled nanostructures. The latter consist of a disordered array of nanopillars and are fabricated by polymer blend lithography. Their broadband light scattering properties are exploited to enhance the photocurrent density of thin film devices, here based on hydrogenated amorphous silicon active layers. We demonstrate that these light scattering nanopillars yield a short-circuit current density increase of +33%rel with respect to equivalent solar cells processed on a planar reflector. Moreover, we experimentally show that they outperform randomly textured substrates that are commonly used for achieving efficient light trapping. Complementary optical simulations are conducted on an accurate 3D model to analyze the superior light harvesting properties of the nanopillar array and to derive general design rules. Our approach allows one to easily tune the morphology of the self-assembled nanostructures, is up-scalable and operated at room temperature, and is applicable to other photovoltaic technologies.

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Cellulose substrates for PV applications present a fibrous surface texture that is not suitable for the uniform deposition of thin‐film solar cells causing poor device performance. However, uniform thin‐film deposition and efficient light management for solar cells can be achieved on cellulose substrates by transferring well‐known surface textures that provide an adequate surface for thin film solar cell deposition and also, provide light scattering properties into the cellulose surface. In this work, we study the properties of crater‐like textures transferred onto cellulose substrates by nanoimprint lithography and the corresponding effect on the J–V and EQE characteristics of amorphous silicon thin‐film solar cells. The prototype solar cells are deposited on cellulose substrates and the results are compared with the results of such solar cells deposited on flat glass substrates. The results show that the J–V characteristics of solar cells deposited on planar as well as textured glass substrates are well reproduced. Due to the process routine, the solar cells on the cellulose substrate with nanoimprinted textures show an increase in the short circuit current density and power conversion efficiency over previous results in our laboratory.