Dopant-free planar n-i-p perovskite solar cells with steady-state efficiencies exceeding 18%
ACS Energy Letters American Chemical Society 2:3 (2017) 622-628
Abstract:
In this Letter, we demonstrate a planar n–i–p perovskite solar cell design with a steady-state efficiency of up to 18.8% in the absence of any electronic dopants. In the device stack, solution-processed SnO2 is used as an electron-accepting n-type layer. The absorber layer is a perovskite with both mixed organic A-site cations and mixed halides (FA0.83MA0.17Pb(I0.83Br0.17)3). The hole-transporting p-type layer is a double-layer structure of polymer-wrapped single-walled carbon nanotubes and undoped spiro-OMeTAD. We show that this approach can deliver steady-state efficiencies as high as and even higher than those of traditionally doped spiro-OMeTAD, providing a pathway for dopant-free perovskite solar cells crucial for long-term stability.Carbon nanotubes in perovskite solar cells
Advanced Energy Materials Wiley 7:10 (2016) 601839
Abstract:
The remarkable optoelectronic properties of metal halide perovskite absorbers have, in the past years, made the perovskite solar cell one of the most promising emerging photovoltaic technologies. The charge collecting layers are essential parts of this type of solar cell. Carbon nanotubes have emerged as a potential candidate to take on this role. Equipped with a range of highly beneficial properties including excellent charge transport characteristics, chemical inertness, as well as mechanical robustness, carbon nanotubes are able to both efficiently extract photogenerated charges, and improve the resilience and stability of a perovskite solar cell. In this Research News article we give a concise overview of the current state-of-the-art of perovskite solar cells in which carbon nanotubes are incorporated as a charge conduction layer.A low viscosity, low boiling point, clean solvent system for the rapid crystallisation of highly specular perovskite films
Energy and Environmental Science Royal Society of Chemistry 10:1 (2016) 145-152
Abstract:
Perovskite-based photovoltaics have, in recent years, become poised to revolutionise the solar industry. While there have been many approaches taken to the deposition of this material, one-step spin-coating remains the simplest and most widely used method in research laboratories. Although spin-coating is not recognised as the ideal manufacturing methodology, it represents a starting point from which more scalable deposition methods, such as slot-dye coating or ink-jet printing can be developed. Here, we introduce a new, low-boiling point, low viscosity solvent system that enables rapid, room temperature crystallisation of methylammonium lead triiodide perovskite films, without the use of strongly coordinating aprotic solvents. Through the use of this solvent, we produce dense, pinhole free films with uniform coverage, high specularity, and enhanced optoelectronic properties. We fabricate devices and achieve stabilised power conversion efficiencies of over 18% for films which have been annealed at 100 °C, and over 17% for films which have been dried under vacuum and have undergone no thermal processing. This deposition technique allows uniform coating on substrate areas of up to 125 cm2, showing tremendous promise for the fabrication of large area, high efficiency, solution processed devices, and represents a critical step towards industrial upscaling and large area printing of perovskite solar cells.Investigating the role of 4-tert butylpyridine in perovskite solar cells
Advanced Energy Materials Wiley 7:1 (2016) 1601079
Abstract:
The majority of hole‐transporting layers used in n‐i‐p perovskite solar cells contain 4‐tert butylpyridine (tBP). High power‐conversion efficiencies and, in particular, good steady‐state performance appears to be contingent on the inclusion of this additive. On the quest to improve the steady state efficiencies of the carbon nanotube‐based hole‐transporter system, this study has found that the presence of tBP results in an extraordinary improvement in the performance of these devices. By deconstructing a prototypical device and investigating the effect of tBP on each individual layer, the results of this study indicate that this performance enhancement must be due to a direct chemical interaction between tBP and the perovskite material. This study proposes that tBP serves to p‐dope the perovskite layer and investigates this theory with poling and work function measurements.Research update: Strategies for improving the stability of perovskite solar cells
APL Materials AIP Publishing 4:9 (2016) 091503