ORCID Profile
0000-0001-6618-8403
Current Organisation
University of Potsdam
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Publisher: American Chemical Society (ACS)
Date: 07-01-2021
Publisher: AIP Publishing
Date: 10-2021
DOI: 10.1063/5.0047616
Abstract: Metal halide perovskites are the first solution processed semiconductors that can compete in their functionality with conventional semiconductors, such as silicon. Over the past several years, perovskite semiconductors have reported breakthroughs in various optoelectronic devices, such as solar cells, photodetectors, light emitting and memory devices, and so on. Until now, perovskite semiconductors face challenges regarding their stability, reproducibility, and toxicity. In this Roadmap, we combine the expertise of chemistry, physics, and device engineering from leading experts in the perovskite research community to focus on the fundamental material properties, the fabrication methods, characterization and photophysical properties, perovskite devices, and current challenges in this field. We develop a comprehensive overview of the current state-of-the-art and offer readers an informed perspective of where this field is heading and what challenges we have to overcome to get to successful commercialization.
Publisher: American Chemical Society (ACS)
Date: 15-01-2021
Publisher: Research Square Platform LLC
Date: 20-01-2023
DOI: 10.21203/RS.3.RS-2495973/V1
Abstract: In the last decade, perovskite semiconductors have triggered a revolution in solar cell research. However, critical issues remain concerning the stability of metal-halide perovskites, which need to be overcome to enable a large scale commercialisation of perovskite photovoltaics (PV). While the rather poor environmental stability of these perovskites is usually attributed to their ionic nature rendering them sensitive to moisture and oxygen, the actual contribution of mobile ions to the total degradation loss under different environmental conditions is poorly understood. In this work, we reveal that the initial degradation of perovskite semiconductors is largely the result of mobile ion-induced internal field screening - a phenomenon that has not been previously discussed in relation to the degradation of perovskite solar cells. The increased field screening leads to a decrease in the steady-state power conversion efficiency mainly due to a large reduction in current density, while the efficiency at high scan speeds ( V/s) where the ions are immobilized is much less affected. We also show that interfacial recombination does not increase upon ageing, yet the open-circuit voltage (VOC) decreases as the result of an increase in the mobile ion density upon ageing. Furthermore, similar ionic losses appear under different external stressors, in particular when there are free charges present in the absorber layer. This work reveals a key degradation mechanism, providing new insights into initial device degradation before chemical or extrinsic mechanical device degradation effects manifest, and it highlights the critical role mobile ions play therein.
Publisher: American Chemical Society (ACS)
Date: 22-09-2023
Publisher: AIP Publishing
Date: 06-2023
DOI: 10.1063/5.0151580
Abstract: Understanding the origin of inefficient photocurrent generation in organic solar cells with low energy offset remains key to realizing high-performance donor-acceptor systems. Here, we probe the origin of field-dependent free-charge generation and photoluminescence in non-fullereneacceptor (NFA)-based organic solar cells using the polymer PM6 and the NFA Y5—a non-halogenated sibling to Y6, with a smaller energetic offset to PM6. By performing time-delayed collection field (TDCF) measurements on a variety of s les with different electron transport layers and active layer thickness, we show that the fill factor and photocurrent are limited by field-dependent free charge generation in the bulk of the blend. We also introduce a new method of TDCF called m-TDCF to prove the absence of artifacts from non-geminate recombination of photogenerated and dark charge carriers near the electrodes. We then correlate free charge generation with steady-state photoluminescence intensity and find perfect anticorrelation between these two properties. Through this, we conclude that photocurrent generation in this low-offset system is entirely controlled by the field-dependent dissociation of local excitons into charge-transfer states.
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D1EE02650J
Abstract: We identify the limiting factors of wide bandgap metal halide perovskite solar cells. To overcome these losses, we developed an efficient optimisation strategy and outline the necessary steps for the continued development of these perovskites.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D0EE02216K
Abstract: Tuning the energy levels of halide perovskite by controlling the deposition of dipolar self-assembled monolayers.
Publisher: Royal Society of Chemistry (RSC)
Date: 2022
DOI: 10.1039/D2TC01918C
Abstract: A systematic spectroelectrochemical approach is presented to precisely determine frontier orbital energies of PM6:Y6 blends in device-relevant films and results are discussed regarding their impact on solar cell performance.
Publisher: Wiley
Date: 19-06-2023
Abstract: As a direct‐bandgap transition semiconductor with high carrier mobility, monolayer (ML) transition metal dichalcogenides (TMDCs) have attracted significant attention as a promising class of material for photodetection. It is reported that these layers exhibit a persistent photoconductance (PPC) effect, which is assigned to long‐lasting hole capture by deep traps. Therefore, TMDCs‐based photodetectors show a high photoresponse but also a slow response. Herein, intensity‐modulated photocurrent spectroscopy (IMPS) with steady‐state background illumination is performed to investigate the photoresponse dynamics in a hybrid photodetector based on ML MoS 2 covered with an ultrathin layer of phthalocyanine (H 2 Pc) molecules. The results demonstrate that adding the H 2 Pc layer speeds up the photoresponse of the neat ML‐MoS 2 photodetector by almost two orders of magnitude without deteriorating its responsivity. The origin of these improvements is revealed by applying the Hornbeck–Haynes model to the photocarrier dynamics in the IMPS experiment. It is shown that the improved response speed of the hybrid device arises mostly from a faster detrapping of holes in the presence of the H 2 Pc layer, while the trap densities remain rather unchanged. Meanwhile, the additional absorption of photons in the H 2 Pc layer contributes to photocarrier generation, resulting in an enlarged responsivity of the hybrid device.
Publisher: Springer Science and Business Media LLC
Date: 20-02-2023
DOI: 10.1038/S41467-023-36141-8
Abstract: In this work, we couple theoretical and experimental approaches to understand and reduce the losses of wide bandgap Br-rich perovskite pin devices at open-circuit voltage (V OC ) and short-circuit current (J SC ) conditions. A mismatch between the internal quasi-Fermi level splitting (QFLS) and the external V OC is detrimental for these devices. We demonstrate that modifying the perovskite top-surface with guanidinium-Br and imidazolium-Br forms a low-dimensional perovskite phase at the n -interface, suppressing the QFLS-V OC mismatch, and boosting the V OC . Concurrently, the use of an ionic interlayer or a self-assembled monolayer at the p -interface reduces the inferred field screening induced by mobile ions at J SC , promoting charge extraction and raising the J SC . The combination of the n- and p- type optimizations allows us to approach the thermodynamic potential of the perovskite absorber layer, resulting in 1 cm 2 devices with performance parameters of V OC s up to 1.29 V, fill factors above 80% and J SC s up to 17 mA/cm 2 , in addition to a thermal stability T 80 lifetime of more than 3500 h at 85 °C.
Publisher: American Chemical Society (ACS)
Date: 17-06-2020
Publisher: American Chemical Society (ACS)
Date: 20-02-2019
Publisher: American Chemical Society (ACS)
Date: 17-07-2020
Publisher: Wiley
Date: 08-08-2021
Abstract: Interfaces play a crucial role in determining perovskite solar cells, (PSCs) performance and stability. It is therefore of great importance to constantly work toward improving their design. This study shows the advantages of using a hole‐transport material (HTM) that can anchor to the perovskite surface through halogen bonding (XB). A halo‐functional HTM (PFI) is compared to a reference HTM (PF), identical in optoelectronic properties and chemical structure but lacking the ability to form XB. The interaction between PFI and perovskite is supported by simulations and experiments. XB allows the HTM to create an ordered and homogenous layer on the perovskite surface, thus improving the perovskite/HTM interface and its energy level alignment. Thanks to the compact and ordered interface, PFI displays increased resistance to solvent exposure compared to its not‐interacting counterpart. Moreover, PFI devices show suppressed nonradiative recombination and reduced hysteresis, with a V oc enhancement of ≥20 mV and a remarkable stability, retaining more than 90% efficiency after 550 h of continuous maximum‐power‐point tracking. This work highlights the potential that XB can bring to the context of PSCs, paving the way for a new halo‐functional design strategy for charge‐transport layers, which tackles the challenges of charge transport and interface improvement simultaneously.
No related grants have been discovered for Dieter Neher.