Electromagnetic absorbers have drawn increasing attention in many areas. A series of plasmonic and metamaterial structures can work as efficient narrowband absorbers due to the excitation of plasmonic or photonic resonances, providing a great potential for applications in designing selective thermal emitters, biosensing, etc. In other applications such as solar-energy harvesting and photonic detection, the bandwidth of light absorbers is required to be quite broad. Under such a background, a variety of mechanisms of broadband/multiband absorption have been proposed, such as mixing multiple resonances together, exciting phase resonances, slowing down light by anisotropic metamaterials, employing high loss materials and so on.

Three-dimensional (3-D) structures have triggered tremendous interest for thin-film solar cells since they can dramatically reduce the material usage and incident light reflection. However, the high aspect ratio feature of some 3-D structures leads to deterioration of internal electric field and carrier collection capability, which reduces device power conversion efficiency (PCE). Here, we report high performance flexible thin-film amorphous silicon solar cells with a unique and effective light trapping scheme. In this device structure, a polymer nanopillar membrane is attached on top of a device, which benefits broadband and omnidirectional performances, and a 3-D nanostructure with shallow dent arrays underneath serves as a back reflector on flexible titanium (Ti) foil resulting in an increased optical path length by exciting hybrid optical modes. The efficient light management results in 42.7% and 41.7% remarkable improvements of short-circuit current density and overall efficiency, respectively. Meanwhile, an excellent flexibility has been achieved as PCE remains 97.6% of the initial efficiency even after 10 000 bending cycles. This unique device structure can also be duplicated for other flexible photovoltaic devices based on different active materials such as CdTe, Cu(In,Ga)Se2 (CIGS), organohalide lead perovskites, and so forth.

Molybdenum trioxide (MoOX, X < 3), with a large work function, can induce upward band bending in crystalline silicon (c‐Si) when constructing a heterojunction, which makes it an attractive candidate for hole‐selective contact in c‐Si solar cells. Herein, the passivation property and hole selectivity of MoOX thin films are investigated on p‐type c‐Si wafers using MoOX/aluminum (Al) as rear contacts. To elevate the performance from the aspect of light management, silver (Ag) and copper (Cu) are further used as back electrodes instead of Al. Solar cells with Ag electrodes deliver the best performance with a power conversion efficiency of 18.74%, followed by Cu (17.61%) and Al (16.36%) electrodes, attributing to the better reflectivity of Ag and Cu. It is also noted that solar cells with MoOX/Ag and MoOX/Cu contacts show significant degradation under room temperature storage. The interfacial evolutions are then carefully studied as a function of elevated temperature that accelerate the thermodynamic process. The degradation mechanism involves redox reaction and metal diffusion at the MoOX/metal interfaces. This work points out the importance of selecting the adjacent layers of MoOX and regulating the interfaces to stabilize the MoOX‐based c‐Si solar cells.