Search

Perovskite/silicon tandem solar cells (TSCs) are promising candidates for commercialization due to their outstanding power conversion efficiencies (PCEs). However, controlling the crystallization process and alleviating the phases/composition inhomogeneity represent a considerable challenge for perovskite layers grown on rough silicon substrates, ultimately limiting the efficiency and stability of TSC. Here, this study reports a "halide locking" strategy that simultaneously modulates the nucleation and crystal growth process of wide bandgap perovskites by introducing a multifunctional ammonium salt, thioacetylacetamide hydrochloride (TAACl), to bind with all types of cations and anions in the mixed halide perovskite precursor. The approach not only enables excellent compositional uniformity in the wet-film stage but also induces preferred orientation along the (001) plane following nucleation, leading to enhanced homogeneity of the perovskite film in both vertical and horizontal directions over long-length scales. The resulting wide-bandgap perovskite solar cells yield exceptional open-circuit voltage-fill factor products (V OC × FF) of 1.074 and 1.040 in small- (0.0414 cm 2 ) and large-area (1.0208 cm 2 ) devices, respectively. Corresponding large-area tandem solar cells based on the Tunnel Oxide Passivated Contact (TOPCon) silicon subcells achieve a record PCE of 31.32% with a remarkable V OC of 1.931 V and FF of 81.54%., (© 2025 Wiley‐VCH GmbH.)

Perovskite/organic tandem solar cells (POTSCs) have garnered significant attention due to their potential for achieving high photovoltaic (PV) performance. However, the reported power conversion efficiencies (PCEs) and fill factors (FFs) are still subpar due to the challenges associated with charge extraction in the organic bulk-heterojunction (BHJ) and significant energy losses in the interconnecting layers (ICLs). Here, a quaternary organic BHJ blend is developed to enhance the charge extraction in the organic subcell, contributing to an increased FF of ≥78% under 1 sun illumination and even more under lower illumination intensities. Meanwhile, energy losses in the ICLs are reduced via the incorporation of a self-assembly monolayer (SAM), (4-(3,6-Dimethyl-9H-carbazol-9-yl)butyl)phosphonic acid (Me-4PACz), in organic BHJ to form a MoO x /SAM interface and the thorough control of the MoO x thickness to suppress parasitic absorption. The resultant POTSCs achieve a remarkable PCE of 25.56% (certified: 24.65%), with a record FF of 83.62%, which is among the highest PCEs of POTSCs and the highest FF of all types of perovskite-based tandem solar cells (TSCs) till now. This work proves the optimization of charge extraction and ICLs are effective strategies to promote the performance of POTSCs to surpass other solution-processed perovskite-based TSCs in the near future., (© 2024 Wiley‐VCH GmbH.)

All-perovskite tandem solar cells show great potential to enable the highest performance at reasonable costs for a viable market entry in the near future. In particular, wide-bandgap (WBG) perovskites with higher open-circuit voltage (V OC ) are essential to further improve the tandem solar cells' performance. Here, a new 1.8 eV bandgap triple-halide perovskite composition in conjunction with a piperazinium iodide (PI) surface treatment is developed. With structural analysis, it is found that the PI modifies the surface through a reduction of excess lead iodide in the perovskite and additionally penetrates the bulk. Constant light-induced magneto-transport measurements are applied to separately resolve charge carrier properties of electrons and holes. These measurements reveal a reduced deep trap state density, and improved steady-state carrier lifetime (factor 2.6) and diffusion lengths (factor 1.6). As a result, WBG PSCs achieve 1.36 V V OC , reaching 90% of the radiative limit. Combined with a 1.26 eV narrow bandgap (NBG) perovskite with a rubidium iodide additive, this enables a tandem cell with a certified scan efficiency of 27.5%., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

Perovskite photovoltaic (PV) cells have demonstrated power conversion efficiencies (PCE) that are close to those of monocrystalline silicon cells; however, in contrast to silicon PV, perovskites are not limited by Auger recombination under 1-sun illumination. Nevertheless, compared to GaAs and monocrystalline silicon PV, perovskite cells have significantly lower fill factors due to a combination of resistive and non-radiative recombination losses. This necessitates a deeper understanding of the underlying loss mechanisms and in particular the ideality factor of the cell. By measuring the intensity dependence of the external open-circuit voltage and the internal quasi-Fermi level splitting (QFLS), the transport resistance-free efficiency of the complete cell as well as the efficiency potential of any neat perovskite film with or without attached transport layers are quantified. Moreover, intensity-dependent QFLS measurements on different perovskite compositions allows for disentangling of the impact of the interfaces and the perovskite surface on the non-radiative fill factor and open-circuit voltage loss. It is found that potassium-passivated triple cation perovskite films stand out by their exceptionally high implied PCEs > 28%, which could be achieved with ideal transport layers. Finally, strategies are presented to reduce both the ideality factor and transport losses to push the efficiency to the thermodynamic limit., (© 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Organic solar cells are currently experiencing a second golden age thanks to the development of novel non-fullerene acceptors (NFAs). Surprisingly, some of these blends exhibit high efficiencies despite a low energy offset at the heterojunction. Herein, free charge generation in the high-performance blend of the donor polymer PM6 with the NFA Y6 is thoroughly investigated as a function of internal field, temperature and excitation energy. Results show that photocurrent generation is essentially barrierless with near-unity efficiency, regardless of excitation energy. Efficient charge separation is maintained over a wide temperature range, down to 100 K, despite the small driving force for charge generation. Studies on a blend with a low concentration of the NFA, measurements of the energetic disorder, and theoretical modeling suggest that CT state dissociation is assisted by the electrostatic interfacial field which for Y6 is large enough to compensate the Coulomb dissociation barrier., (© 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Perovskite solar cells combine high carrier mobilities with long carrier lifetimes and high radiative efficiencies. Despite this, full devices suffer from significant nonradiative recombination losses, limiting their V OC to values well below the Shockley-Queisser limit. Here, recent advances in understanding nonradiative recombination in perovskite solar cells from picoseconds to steady state are presented, with an emphasis on the interfaces between the perovskite absorber and the charge transport layers. Quantification of the quasi-Fermi level splitting in perovskite films with and without attached transport layers allows to identify the origin of nonradiative recombination, and to explain the V OC of operational devices. These measurements prove that in state-of-the-art solar cells, nonradiative recombination at the interfaces between the perovskite and the transport layers is more important than processes in the bulk or at grain boundaries. Optical pump-probe techniques give complementary access to the interfacial recombination pathways and provide quantitative information on transfer rates and recombination velocities. Promising optimization strategies are also highlighted, in particular in view of the role of energy level alignment and the importance of surface passivation. Recent record perovskite solar cells with low nonradiative losses are presented where interfacial recombination is effectively overcome-paving the way to the thermodynamic efficiency limit., (© 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

2D Ruddlesden-Popper perovskite (RPP) solar cells have excellent environmental stability. However, the power conversion efficiency (PCE) of RPP cells remains inferior to 3D perovskite-based cells. Herein, 2D (CH 3 (CH 2 ) 3 NH 3 ) 2 (CH 3 NH 3 ) n -1 Pb n I 3 n +1 perovskite cells with different numbers of [PbI 6 ] 4- sheets (n = 2-4) are analyzed. Photoluminescence quantum yield (PLQY) measurements show that nonradiative open-circuit voltage (V OC ) losses outweigh radiative losses in materials with n > 2. The n = 3 and n = 4 films exhibit a higher PLQY than the standard 3D methylammonium lead iodide perovskite although this is accompanied by increased interfacial recombination at the top perovskite/C 60 interface. This tradeoff results in a similar PLQY in all devices, including the n = 2 system where the perovskite bulk dominates the recombination properties of the cell. In most cases the quasi-Fermi level splitting matches the device V OC within 20 meV, which indicates minimal recombination losses at the metal contacts. The results show that poor charge transport rather than exciton dissociation is the primary reason for the reduction in fill factor of the RPP devices. Optimized n = 4 RPP solar cells had PCEs of 13% with significant potential for further improvements., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)