Annual energy yield of mono- and bifacial silicon heterojunction solar modules with high-index dielectric nanodisk arrays as anti-reflective and light trapping structures.

While various nanophotonic structures applicable to relatively thin crystalline silicon-based solar cells were proposed to ensure effective light in-coupling and light trapping in the absorber, it is of great importance to evaluate their performance on the solar module level under realistic irradiation conditions. Here, we analyze the annual energy yield of relatively thin (crystalline silicon (c-Si) wafer thickness between 5 µm and 80 µm) heterojunction (HJT) solar module architectures when optimized anti-reflective and light trapping titanium dioxide (TiO2) nanodisk square arrays are applied on the front and rear cell interfaces, respectively. Our numerical study shows that upon reducing c-Si wafer thickness down to 5 µm, the relative increase of the annual energy yield can go up to 23.3 %rel and 43.0 %rel for mono- and bifacial solar modules, respectively, when compared to the reference modules with flat optimized anti-reflective coatings of HJT solar cells.

Liquid Glass for Photovoltaics: Multifunctional Front Cover Glass for Solar Modules.

Advanced optical concepts, making use of tailored microstructured front cover glasses, promise to reduce the losses encountered with encapsulated solar modules. However, implementing optical concepts into the conventional architecture of encapsulated solar modules and simultaneously maintaining high durability represent a severe technological challenge. The liquid glass technique offers a route to meet this challenge by enabling the implementation of these optical concepts directly into the durable front cover glass of solar modules. In this work, we demonstrate for the first time two showcases of texturing fused silica front cover glass, using the facile liquid glass technique: (I) multifunctional microcone textures that reduce front-side reflection losses by ∼80% compared to a planar reference, which correlates to an increase in short-circuit current density of encapsulated planar monocrystalline silicon heterojunction solar cells by 2.9 mA cm-2, and exhibit strong hydrophilic behavior facilitating self-cleaning and (II) embedded freeform surface cloaks that redirect incident light away from the metallic contact grids of the solar cell and demonstrate a cloaking efficiency of ∼88%.

Methodology of energy yield modelling of perovskite-based multi-junction photovoltaics.

Energy yield (EY) modelling is an indispensable tool to minimize payback time of emerging perovskite-based multi-junction photovoltaics (PV) but it relies on many assumptions about device architecture and environmental conditions. Here, we propose a comprehensive framework that enables rapid simulation of complex architectures of perovskite-based multi-junction PV and detailed calculation of their power output under realistic irradiation conditions in various climatic zones. Applying the framework to perovskite/silicon multi-junction solar modules, we showcase the impact of tracking on energy losses arising from spectral variations. Moreover, we demonstrate the strong dependency of the EY of bifacial multi-junction solar modules on the albedo.

Light Management: A Key Concept in High-Efficiency Perovskite/Silicon Tandem Photovoltaics.

The remarkable recent progress in perovskite photovoltaics affords a novel opportunity to advance the power conversion efficiency of market-dominating crystalline silicon (c-Si) solar cells. A severe limiting factor in the development of perovskite/c-Si tandems to date has been their inferior light-harvesting ability compared to single-junction c-Si solar cells, but recent innovations have made impressive headway on this front. Here, we provide a quantitative perspective on future steps to advance perovskite/c-Si tandem photovoltaics from a light-management point of view, addressing key challenges and available strategies relevant to both the 2-terminal and 4-terminal perovskite/c-Si tandem architectures. In particular, we discuss the challenge of achieving low optical reflection in 2-terminal cells, optical shortcomings in state-of-the-art devices, the impact of transparent electrode performance, and a variety of factors which influence the optimal bandgap for perovskite top-cells. Focused attention in each of these areas will be required to make the most of the tandem opportunity.

Exposure-dependent refractive index of Nanoscribe IP-Dip photoresist layers.

The refractive indices of photoresists used for direct laser writing (DLW) have been determined after exposure to ultraviolet (UV) light. However, it was anticipated that the refractive index will differ when applying a two-photon polymerization (TPP) process. In this Letter, we demonstrate that this is indeed the case. Making use of a guided mode coupling approach, we measure the dispersive real part of the refractive index (n) of a commercial photoresist (IP-Dip, Nanoscribe) at very high accuracy. Additionally, the imaginary part of the refractive index (k) is determined from absorption measurements for wavelengths in the range 300 to 1700 nm. TPP layers exhibit a significantly lower refractive index than their UV exposed bulk counterparts (Δn up to 0.01). Furthermore, when fabricating a TPP shell and UV exposing the interior, the refractive index of the shell will not change. This is an important consideration for optical component design and opens the possibility for low refractive index difference wave guiding.