Perovskites have been firmly established as one of the most promising materials for third-generation solar cells. There remain several great and lingering challenges to be addressed regarding device efficiency and stability. The photovoltaic efficiency of perovskite solar cells (PSCs) depends drastically on the charge-carrier dynamics. This complex process includes charge-carrier generation, extraction, transport and collection, each of which needs to be modulated in a favorable manner to achieve high performance. Two-dimensional materials (TDMs) including graphene and its derivatives, transition metal dichalcogenides ( e.g. , MoS 2 , WS 2 ), black phosphorus (BP), metal nanosheets and two-dimensional (2D) perovskite active layers have attracted much attention for application in perovskite solar cells due to their high carrier mobility and tunable work function properties which greatly impact the charge carrier dynamics of PSCs. To date, significant advances have been achieved in the field of TDM-based PSCs. In this review, the recent progress in the development and application of TDMs ( i.e. , graphene, graphdiyne, transition metal dichalcogenides, BP, and others) as electrodes, hole transporting layers, electron transporting layers and buffer layers in PSCs is detailed. 2D perovskites as active absorber materials in PSCs are also summarized. The effect of TDMs and 2D perovskites on the charge carrier dynamics of PSCs is discussed to provide a comprehensive understanding of their optoelectronic processes. The challenges facing the PSC devices are emphasized with corresponding solutions to these problems provided with the overall goal of improving the efficiency and stability of photovoltaic devices.
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Integration of a functionalized graphene nano-network into a planar perovskite absorber for high-efficiency large-area solar cells
Efficient charge collection is critical in large area (quasi-) planar configuration perovskite solar cells (PSCs) as the cell operation relies on the diffusion of photo-generated charge carriers to charge collector layers. Many defects/traps in the polycrystalline perovskite absorber layer strongly affect the charge collection efficiency because the 2D-like top charge collection layer barely penetrates into the 3D grain boundaries in the perovskite layer to efficiently collect the charge carrier. Inspired by blood capillaries for efficient mass exchange, a charge-collection nano-network for efficient charge collection was incorporated into the perovskite absorber using low-cost, stable amino-functionalized graphene (G-NH 2 ). The integration of such an unprecedented structure enables very efficient charge collection, leading to the significant enhancement of the power conversion efficiency of 1 × 1 cm 2 MAPbI 3 PSCs from 14.4 to 18.7% with higher reproducibility, smaller hysteresis and enhanced stability. The physicochemical mechanisms underlying the role of this nano charge-collection nano-network in boosting the charge collection in PSCs are elucidated comprehensively, using a combined experimental and theoretical approach, pointing to a new direction towards up-scaling of high-efficiency PSCs.
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- Award ID(s):
- 1538893
- NSF-PAR ID:
- 10092614
- Date Published:
- Journal Name:
- Materials Horizons
- Volume:
- 5
- Issue:
- 5
- ISSN:
- 2051-6347
- Page Range / eLocation ID:
- 868 to 873
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Flexible perovskite solar cells (
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In a mesoporous hybrid perovskite solar cell (PSC), the mesoporous scaffold plays key roles in controlling the crystallization of the perovskite material and in the charge carrier transport, and hence is critical for developing highly efficient PSCs. Here we report a study on blending micrometer-long TiO 2 nanorods (NRs) into the commonly used nanoparticles (NPs) to optimize the mesoporous structure, with the aim of enhancing the perovskite material loading and connectivity as well as light harvesting. It was found that with 5–10% of NR incorporation, a uniform scaffold can be spin-coated and the PSC performance was improved. In comparison to the pure NP-based device, the power conversion efficiency was increased by about 27% when 10% of the NRs were incorporated, due to enhanced light harvesting and charge collection. However, with more NR blending, a homogeneous scaffold cannot be formed, resulting in PSC performance degradation. These findings contribute to a better design of mesoporous scaffolds for high-performance PSCs.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/C8MH00511G
