The performance of state-of-the-art perovskite solar cells is currently limited by defectinduced recombination at interfaces between the perovskite and the electron and hole transport layers. These defects, most likely under-coordinated Pb and halide ions, must either be removed or passivated if cell efficiencies are to approach their theoretical limit. In this work, we introduce a universal double-side polymer passivation approach using ultrathin poly(methyl methacrylate) (PMMA) films. We demonstrate very high-efficiency (~20.8%) perovskite cells with some of the highest open circuit voltages (1.22 V) reported for the same 1.6 eV bandgap. Photoluminescence imaging and transient spectroscopic measurements confirm a significant reduction in non-radiative recombination in the passivated cells, consistent with the voltage increase. Analysis of the molecular interactions between Received: ((will be filled in by the editorial staff)) Revised: ((will be filled in by the editorial staff))

Polymer passivation layers can improve the open-circuit voltage of perovskite solar cells when inserted at the perovskite–charge transport layer interfaces. Unfortunately, many such layers are poor conductors, leading to a trade-off between passivation quality (voltage) and series resistance (fill factor, FF). Here, we introduce a nanopatterned electron transport layer that overcomes this trade-off by modifying the spatial distribution of the passivation layer to form nanoscale localized charge transport pathways through an otherwise passivated interface, thereby providing both effective passivation and excellent charge extraction. By combining the nanopatterned electron transport layer with a dopant-free hole transport layer, we achieved a certified power conversion efficiency of 21.6% for a 1-square-centimeter cell with FF of 0.839, and demonstrate an encapsulated cell that retains ~91.7% of its initial efficiency after 1000 hours of damp heat exposure.

Rapid development of both efficiency 1 and stability 2 mean that perovskite solar cells are at the forefront of emerging photovoltaic technologies. State-of-the-art cells exhibit voltage losses 3-8 approaching the theoretical minimum and near-unity internal quantum efficiency 9-13 , but conversion efficiencies are limited by the fill-factor (FF < 83%, below the Shockley-Queisser limit of ~90%). This limitation results from non-ideal charge transport between the perovskite absorber and the cell's electrodes 5,8,13-16 . Reducing the electrical series resistance of charge transport layers is therefore crucial for improving efficiency. Here we introduce a reverse-doping process to fabricate nitrogen-doped titanium oxide electron transport layers with outstanding charge transport performance. By incorporating this charge transport material into perovskite solar cells, we demonstrate 1cm 2 cells with FFs >86%, and an average FF ~ 85.3%. We also report a certified steady-state efficiency record of 22.6% for a 1cm 2 cell (23.33% ± 0.58% from reverse current-voltage scan).Nitrogen-doped titanium oxide (titanium oxynitride, TiO x N y ) has been widely investigated for photocatalysis 17,18 , but rarely in perovskite solar cells (PSCs). PSCs incorporating solution-processed TiO x N y have been reported, but device performances have

Parasitic absorption in transparent electrodes is one of the main roadblocks to enable power conversion efficiencies (PCEs) for perovskite-based tandem solar cells beyond 30%. To reduce such losses and maximize light coupling, the broadband transparency of such electrodes should be improved, especially at the front of the device. Here, we show the excellent properties of Zr-doped indium oxide (IZRO) transparent electrodes for such applications, with improved near-infrared (NIR) response, compared to conventional In-doped tin oxide (ITO) electrodes. Optimized IZRO films feature a very high electron mobility (up to ~77 cm 2 /V•s), enabling highly infrared transparent films with very low sheet resistance (~18 for annealed 100 nm films). For devices, this translates in a parasitic absorption of only ~5% for IZRO within the solar spectrum (250-2500 nm range), to be compared with ~10% for commercial ITO. Fundamentally, we find that the high conductivity of annealed IZRO films is directly linked to promoted crystallinity of the indium oxide (In2O3) films due to Zr-doping. Overall, on four-terminal perovskite/silicon tandem device level, we obtained an absolute 3.5

Minimizing carrier recombination at contact regions by using carrier‐selective contact materials, instead of heavily doping the silicon, has attracted considerable attention for high‐efficiency, low‐cost crystalline silicon (c‐Si) solar cells. A novel electron‐selective, passivating contact for c‐Si solar cells is presented. Tantalum nitride (TaN x ) thin films deposited by atomic layer deposition are demonstrated to provide excellent electron‐transporting and hole‐blocking properties to the silicon surface, due to their small conduction band offset and large valence band offset. Thin TaNx interlayers provide moderate passivation of the silicon surfaces while simultaneously allowing a low contact resistivity to n‐type silicon. A power conversion efficiency (PCE) of over 20% is demonstrated with c‐Si solar cells featuring a simple full‐area electron‐selective TaNx contact, which significantly improves the fill factor and the open circuit voltage (Voc) and hence provides the higher PCE. The work opens up the possibility of using metal nitrides, instead of metal oxides, as carrier‐selective contacts or electron transport layers for photovoltaic devices.