Search

Heterojunction perovskite solar cells combine the stability of 2D perovskites and the high efficiency of 3D perovskites, making them an excellent photovoltaic candidate. While heterojunctions with intermixed or gradient perovskites can reduce surface recombination, the aggregation and phase distribution of 2D perovskite induce transport losses, thereby limiting device fill factors. Accordingly, a bulk in situ reconstruction (BISR) strategy is proposed to induce the reconstruction of 3D perovskites on a minim self‐assembled 2D crystal seed, forming heterojunction perovskite that runs through the entire active layer. This facilitates charge extraction, relieves tensile stress, and avoids the decomposition of perovskite on grain boundaries. As a result, the best‐performing heterojunction perovskite solar cells show a high‐power conversion efficiency (PCE) of 24.06% with 82.9% FF for the small‐area device (0.105 cm2) and a superior PCE of 19.2% for the large‐area module (5 × 5 cm2). Importantly, the unencapsulated device shows dramatically improved operational stability, maintaining 87% of its initial efficiency after 8000 h of storage under ambient atmosphere at room temperature. This work provides an effective and simple approach to establish heterojunction perovskite to simultaneously boost the efficiency and stability of PSCs. [ABSTRACT FROM AUTHOR]

Y6 and its derivatives have greatly improved the power conversion efficiency (PCE) of organic photovoltaics (OPVs). Further developing high‐performance Y6 derivative acceptor materials through the relationship between the chemical structures and properties of these materials will help accelerate the development of OPV. Here, machine learning and quantum chemistry are used to understand the structure–property relationships and develop new OPV acceptor materials. By encoding the molecules with an improved one‐hot code, the trained machine learning model shows good predictive performance, and 22 new acceptors with predicted PCE values greater than 17% within the virtual chemical space are screened out. Trends associated with the discovered high‐performing molecules suggest that Y6 derivatives with medium‐length side chains have higher performance. Further quantum chemistry calculations reveal that the end acceptor units mainly affect the frontier molecular orbital energy levels and the electrostatic potential on molecular surface, which in turn influence the performance of OPV devices. A series of promising Y6 derivative candidates is screened out and a rational design guide for developing high‐performance OPV acceptors is provided. The approach in this work can be extended to other material systems for rapid materials discovery and can provide a framework for designing novel and promising OPV materials. [ABSTRACT FROM AUTHOR]

Different facets in perovskite crystals exhibit distinct atomic arrangements, influencing their electronic, physical, and chemical properties. Perovskite films incorporating tin oxide (SnO 2 ) as the electron transport layer face challenges in facet regulation. This study reveals that tea saponin (TS), a natural compound serves as a SnO 2 modifier, facilitates optimal growth of perovskite crystals on the (111) facet. The modification promotes preferential crystal orientation through hydrogen bond and Lewis coordination. TS forms a chelate with SnO 2 , resulting in a smoother film and n-type doping, leading to improved carrier extraction and reduced defects. The TS-modified perovskite solar cells achieve a champion efficiency of 24.2%, leveraging from an obvious enhancement of open-circuit voltage (V oc ) of 1.18 V and fill factor (FF) of 82.8%. The devices also demonstrate enhanced humidity tolerance and storage stability, ensuring improved stability without encapsulation., (© 2024 Wiley‐VCH GmbH.)

Utilizing first-principles calculations, charge transfer doping process of single layer tin selenide (SL-SnSe) via the surface adsorption of various organic molecules was investigated. Effective p-type SnSe, with carrier concentration exceeding 3.59 × 10 13  cm -2 , was obtained upon adsorption of tetracyanoquinodimethane or 2,3,5,6-tetrafluoro-7,7,8,8-tetracyano-quinodimethane on SL-SnSe due to their lowest unoccupied molecular orbitals acting as shallow acceptor states. While we could not obtain effective n-type SnSe through adsorption of tetrathiafulvalene (TTF) or 1,4,5,8-tetrathianaphthalene on pristine SnSe due to their highest occupied molecular orbitals (HOMO) being far from the conduction band edge of SnSe, this disadvantageous situation can be amended by the introduction of an external electric field perpendicular to the monolayer surface. It is found that Sn vac will facilitate charge transfer from TTF to SnSe through introducing an unoccupied gap state just above the HOMO of TTF, thereby partially compensating for the p-type doping effect of Sn vac . Our results show that both effective p-type and n-type SnSe can be obtained and tuned by charge transfer doping, which is necessary to promote its applications in nanoelectronics, thermoelectrics and optoelectronics., (© 2021 IOP Publishing Ltd.)