| AVS 64th International Symposium & Exhibition | |
| Thin Films Division | Wednesday Sessions |
| Session TF-WeM |
| Session: | Thin Film for Photovoltaics |
| Presenter: | Mariadriana Creatore, Eindhoven University of Technology, Netherlands |
| Authors: | Y. Kuang, Eindhoven University of Technology, Netherlands V. Zardetto, Solliance Solar Research, Netherlands R.J. van Gils, Eindhoven University of Technology, Netherlands F. di Giacomo, Solliance Solar Research, Netherlands G. Lucarelli, University of Rome Tor Vergata, Italy W.M.M. Kessels, Eindhoven University of Technology, Netherlands T.M. Brown, University of Rome Tor Vergata, Italy M. Creatore, Eindhoven University of Technology, Netherlands |
| Correspondent: | Click to Email |
Within the class of emerging photovoltaic technologies, perovskite solar cells have exhibited a sky-rocketing conversion efficiency above 20% in just a few years. In this contribution we will address the opportunities which atomic layer deposition (ALD) offers to perovskite solar cells [1] by highlighting the following merits: control on charge carrier transport and recombination processes at complex interfaces [2,3] and compatibility with low-temperature processing [3]. Specifically, two case studies will be presented:
· Plasma-assisted ALD amorphous TiO2 (cycles consisting of Ti(CpMe)(NMe2)3 and O2 plasma exposure steps) has been adopted in MeNH3PbI3 perovskite solar cells in a mesoscopic configuration [2], with the purpose of suppressing charge recombination processes at the ITO/mesoscopic scaffold/perovskite interface. The superior performance of 10 nm thick ALD TiO2 layers (i.e. up to 16% cell efficiency under 1000/m2 illumination and 24% under indoor illumination) with respect to conventionally adopted spray pyrolysis TiO2, is explained by a lower reverse dark current measured for ALD TiO2. This result points out the superior blocking character of the ALD TiO2 layer toward electron-hole recombination, which is also confirmed by the evaluation of the electron lifetime from open circuit voltage decay analysis. Since ALD TiO2 is carried out at temperatures below 150°C, flexible perovskite solar cells built on PET/iTO substrates are also tested, exhibiting a conversion efficiency of 10.8% under indoor illumination, comparable to the one of flexible dye-sensitized solar cells and exceeding the one of flexible a-Si:H solar cells.
· Ultra-thin (15 nm) plasma-assisted ALD amorphous SnO2 (cycles consisting of Sn(NMe2)4 and O2 plasma exposure steps) is adopted as electron transport layer in a Csx(MAyFA1-y)1-xPb(Iz,Br1-z)3 perovskite solar cell in an n-i-p thin film configuration. The solar cell efficiency reaches the value of 15.9±0.5%, while the same solar cell configuration with an electron-beam deposited TiO2 electron transport layer reaches an efficiency of just 10 ±0.5%. UPS analysis shows that the higher efficiency achieved by SnO2 (with respect to TiO2) is due to a better energy level alignment between the SnO2 and perovskite conduction bands, promoting electron transport. Hole transport, instead, is efficiently blocked because of the misalignment between the SnO2 and perovskite valence bands.
References
[1] V. Zardetto et al., Sustainable Energy and Fuels 1,30 (2017)
[2] F. Di Giacomo et al., Nano Energy 30, 460 (2016)
[3] V. Zardetto et al., Solar Energy, accepted (2017)