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Qimu Yuan
D.Phil. Candidate
Clarendon Laboratory Room 246
Phone (office): +44 (0) 1865 272278
Phone (lab): +44 (0) 1865 282649
Email:
qimu.yuan@physics.ox.ac.uk
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Research interests
Vapour Depostion of Perovskite Solar Cells and Charge Transport Layers
Publications
- A templating approach to controlling the growth of coevaporated halide perovskites,
SY Yan, JB Patel, JE Lee, KA Elmestekawy, SR Ratnasingham, QM Yuan, LM Herz, NK Noel, MB Johnston
ACS Energy Lett., 8:4008–4015 (2023)
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pdf | doi:10.1021/acsenergylett.3c01368 ]
Metal halide perovskite semiconductors have shown significant potential for use in photovoltaic (PV) devices. While fabrication of perovskite thin films can be achieved through a variety of techniques, thermal vapor deposition is particularly promising, allowing for high-throughput fabrication. However, the ability to control the nucleation and growth of these materials, particularly at the charge transport layer/perovskite interface, is critical to unlocking the full potential of vapor-deposited perovskite PV. In this study, we explore the use of a templating layer to control the growth of coevaporated perovskite films and find that such templating leads to highly oriented films with identical morphology, crystal structure, and optoelectronic properties independent of the underlying layers. Solar cells incorporating templated FA(0.9)Cs(0.1)PbI(3-x)Cl(x) show marked improvements with steady-state power conversion efficiency over 19.8%. Our findings provide a straightforward and reproducible method of controlling the charge-transport layer/coevaporated perovskite interface, further clearing the path toward large-scale fabrication of efficient PV devices. - Thermally stable perovskite solar cells by all-vacuum deposition,
QM Yuan, KB Lohmann, RDJ Oliver, AJ Ramadan, SY Yan, JM Ball, MG Christoforo, NK Noel, HJ Snaith, LM Herz, MB Johnston
ACS Appl. Mater. Interfaces, 15:772-781 (2023)
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pdf | doi:10.1021/acsami.2c14658 ]
Vacuum deposition is a solvent-free method suitable for growing thin films of metal halide perovskite (MHP) semiconductors. However, most reports of high-efficiency solar cells based on such vacuum-deposited MHP films incorporate solution-processed hole transport layers (HTLs), thereby complicating prospects of industrial upscaling and potentially affecting the overall device stability. In this work, we investigate organometallic copper phthalocyanine (CuPc) and zinc phthalocyanine (ZnPc) as alternative, low-cost, and durable HTLs in all-vacuum-deposited solvent-free formamidinium-cesium lead triodide [CH(NH2)2]0.83Cs0.17PbI3 (FACsPbI3) perovskite solar cells. We elucidate that the CuPc HTL, when employed in an "inverted" p-i-n solar cell configuration, attains a solar-to-electrical power conversion efficiency of up to 13.9%. Importantly, unencapsulated devices as large as 1 cm2 exhibited excellent longterm stability, demonstrating no observable degradation in efficiency after more than 5000 h in storage and 3700 h under 85 degrees C thermal stressing in N2 atmosphere. - Solvent-Free Method for Defect Reduction and Improved Performance of {p-i-n} Vapor-Deposited Perovskite Solar Cells,
KB Lohmann, SG Motti, RDJ Oliver, AJ Ramadan, HC Sansom, QM Yuan, KA Elmestekawy, JB Patel, JM Ball, LM Herz, HJ Snaith, MB Johnston
ACS Energy Lett., 7:1903-1911 (2022)
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pdf | doi:10.1021/acsenergylett.2c00865 ]
As perovskite-based photovoltaics near commercialization, it is imperative to develop industrial-scale defect-passivation techniques. Vapor deposition is a solvent-free fabrication technique that is widely implemented in industry and can be used to fabricate metal-halide perovskite thin films. We demonstrate markably improved growth and optoelectronic properties for vapor-deposited [CH(NH2)2]0.83Cs0.17PbI3 perovskite solar cells by partially substituting PbI2 for PbCl2 as the inorganic precursor. We find the partial substitution of PbI2 for PbCl2 enhances photoluminescence lifetimes from 5.6 ns to over 100 ns, photoluminescence quantum yields by more than an order of magnitude, and charge-carrier mobility from 46 cm2/(V s) to 56 cm2/(V s). This results in improved solar-cell power conversion efficiency, from 16.4% to 19.3% for the devices employing perovskite films deposited with 20% substitution of PbI2 for PbCl2. Our method presents a scalable, dry, and solvent-free route to reducing nonradiative recombination centers and hence improving the performance of vapor-deposited metal-halide perovskite solar cells.
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