The realization of very high efficiency, stable perovskite solar cells fabricated on a large scale at low cost, has the potential to further lower the cost of photovoltaics. This necessitates an understanding of the properties required of the perovskite material, including the carrier mobility. Perovskite cells also feature mobile ionic species, and the impact of these ions on cell performance – and in particular, to what extent and under what circumstances they may limit device performance – is not well understood. Here, we employ an advanced numerical model that allows for the presence of mobile ionic species to probe the relationship between carrier mobility, the presence of ionic species as well as different possible recombination mechanisms within the cell. We show that a high electron and hole conductivity throughout the device is key to avoiding transport losses. For devices operating significantly below their radiative limit, achieving a sufficiently high conductivity requires high carrier mobilities of at least 10cm<sup>2</sup>/V-s. It is shown that the presence of a single mobile ionic species can lead to effective doping of the perovskite bulk, which is detrimental to cell performance by lowering the conductivity of one type of carrier. The results also indicate that increasing cell VOC closer to its radiative limit is also beneficial for reducing transport losses and pushing cell performance closer to its theoretical limit.
With commercial silicon solar cells approaching both practical and theoretical efficiency limits, there is growing research effort to develop new low-cost technologies capable of reaching efficiencies of 30% and beyond. Silicon-based tandems that combine current industrial technology with emerging thin-film PV materials are considered the most cost-effective option for achieving this, with the latest edition of the International Technology Roadmap for Photovoltaics (ITRPV) predicting Si-based tandems to appear in mass production after 2019. The rapid rise of perovskite solar cell performance in the past few years has made perovskites the material of choice as a top cell for such tandems due to their high efficiency and simple, low-cost fabrication.
Optimization of tandems requires detailed knowledge and characterization of the optical and electrical properties of every layer, as well as practical constraints imposed by processing sequences and chemical incompatibilities. This presentation will review the latest progress in perovskite-silicon tandems, including our recent demonstration of a 26.4% 4-terminal tandem, and a 22.8% monolithic tandem based on a diffused-junction silicon homojunction cell. Key challenges and potential pathways for reaching efficiencies of 30% and beyond will be identified and discussed.
Scattering from metal nanoparticles via excitation of surface plasmon (SP) resonances has the potential to dramatically increase the emission of light-emitting devices. A further redshift in the plasmon resonance is possible by overcoating the metal nanoparticles with a high refractive index medium. In this paper we report a red shift in the emission enhancement peak from Silicon on Insulator (SOI) light emitting diodes (LEDs) by overcoating the metal particles with ZnS, as determined by the electroluminescence (EL) spectra. We demonstrate a 7 fold increase in the electroluminescence at 970nm with an evident redshift from 900nm for the uncoated case.
Localized surface plasmons on metallic nanoparticles can be surprisingly efficient at coupling light into or out of a silicon waveguide. We have previously reported a factor of 7 times enhancement in the electroluminescence from a silicon-on-insulator light-emitting diode with silver nanoparticles at a wavelength of 930nm. In this paper we model the scattering enhancement for metal particles on a silicon-on-insulator substrate and show that the shape of the spectrum is well predicted using the scattering cross-section and angular dependence of emission of an ideal dipole on a layered
substrate. This indicates that the scattering and absorption enhancement at long wavelengths is mainly a single-particle effect, in contrast to previous suggestions that it is a waveguide-mediated multi-particle effect. In particular we show that the particle-waveguide interaction leads to a dramatic enhancement of scattered light at long wavelengths compared with the light scattered by metal islands on glass.
Conference Committee Involvement (7)
Physics, Simulation, and Photonic Engineering of Photovoltaic Devices IX
4 February 2020 | San Francisco, California, United States
Physics, Simulation, and Photonic Engineering of Photovoltaic Devices VIII
5 February 2019 | San Francisco, California, United States
Physics, Simulation, and Photonic Engineering of Photovoltaic Devices VII
31 January 2018 | San Francisco, California, United States
Physics, Simulation, and Photonic Engineering of Photovoltaic Devices VI
30 January 2017 | San Francisco, California, United States
Physics, Simulation, and Photonic Engineering of Photovoltaic Devices V
15 February 2016 | San Francisco, California, United States
Physics, Simulation, and Photonic Engineering of Photovoltaic Devices IV
10 February 2015 | San Francisco, California, United States
Physics, Simulation, and Photonic Engineering of Photovoltaic Devices III
3 February 2014 | San Francisco, California, United States