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We present monolithic copper–indium–gallium–diselenide (Cu(In,Ga)Se _2 , CIGSe)-perovskite tandem solar cells with air- or N _2 -transferred NiO _x :Cu with or without self-assembled monolayer (SAM) as a hole-transporting layer (HTL). A champion efficiency of 23.2%, open-circuit voltage (V $_\mathrm{oc}$ ) of 1.69 V, and a fill factor (FF) of 78.3% are achieved for the tandem with N _2 -transferred NiO _x :Cu + SAM. The samples with air-transferred NiO _x :Cu + SAM have V $_\mathrm{oc}$ and FF losses, while those without SAM are heavily shunted. We find via x-ray and UV photoelectron spectroscopy that the air exposure leads to non-negligible loss in the Ni ^2+ species and changes in the NiO _x :Cu’s work function and valence band maxima, both of which can negatively impact the V $_\mathrm{oc}$ and the FF of the tandems. Furthermore, by performing dark lock-in thermography, photoluminescence (PL), and scanning electron microscopy studies, we are able to detect various morphological defects in the tandems with poor performance, such as ohmic shunts originating from defects in the bottom CIGSe cell, or from cracking/delaminating of the perovskite top cell. Finally, by correlating the detected shunts in the tandems with PL-probed bottom device, we can conclude that not all defects in the bottom device induce ohmic shunts in the tandems since the NiO _x :Cu + SAM HTL bi-layer can decouple the growth of the top device from the rough, defect-rich and defect-tolerant bottom device and enable high-performing devices.

We present an experimental study on the influence of annealing temperature on morphological changes of colloidal silver nanoparticles (Ag NPs) and their optical response. Monodisperse colloidal Ag NPs with diameter of 164 nm ± 15 nm have been fabricated by a facile two-step synthesis approach. The annealing effects on the Ag NPs have been investigated by means of optical measurements, scanning electron microscopy, x-ray photoelectron spectroscopy and x-ray diffraction. By annealing up to 440 °C morphology and chemical compositions of the Ag NPs changed. These changes affect the particle size and distribution, surface morphology, crystallinity and, most importantly, the oxidation state of the surface layer. The removal of an oxide layer leads to stronger light scattering from the nanoparticles and decreases parasitic light absorption at wavelengths above 400 nm. Strong light trapping has been observed for a silicon thin film with embedded annealed Ag NPs. This study demonstrates that colloidal Ag NPs for plasmonic solar cells need to be carefully processed and that they can potentially achieve high scatter efficiencies. [ABSTRACT FROM AUTHOR]