About event
Global installed photovoltaic capacity reached one terawatt and starts to be important component of the energy mix we are using. The market is dominated by silicon wafer-based solar cells. The price per watt-peak decreases drastically and the thin film alternatives suffers from the higher system cost due to lower conversion efficiencies. Is there still a place for silicon thin films or other thin film technologies?
The answer is yes and surprisingly a lot! The so called interdigitated back contacted silicon heterojunction solar cell (IBC SHJ), combining both the thin film and wafer based technology, is the conversion efficiency world record holder with 26.7%. The record IBC SHJ cell is fabricated by many photolithography steps, not compatible with mass production. Thus straightforward shadow mask technology is developing. In order to check the profiles of ~10 nm thin passivating IBC prepared by shadow masks on rough substrates, Raman spectroscopy based thickness measurement with resolution bellow 0.2 nm was introduced [1]. Raman in combination with AFM tomography is moreover suitable for characterisation of mixed phase amorphous/nanocrystalline ultrathin films. 3D visualisations of high temperature top selective contacts (TOPCON) will be used as an example.
But since the silicon wafer based technology approaches the practical efficiency limit (the theoretical is at ~29%), the only way how to go beyond 30% is combination of two cells in a so called tandem. By doing that the theoretical limit is shifted to over 40%. Suitable candidates for the second cell accompanying well mastered IBC SHJ cell are halide perovskites. We will discuss the extraordinary properties of this material family [2]. Finally, we introduce a simple semiconductor property dictating the maximal open circuit voltage obtainable with the given material [3]. In this way we can rapidly preselect suitable candidates for top tandem cell.
References
[1] M. Ledinský, B. Paviet-Salomon, A. Vetushka, J. Geissbühler, A. Tomasi, M. Despeisse, S. De Wolf , C. Ballif and A. Fejfar: Sci. Rep. 6, 37859 (2016).
[2] De Wolf, S.; Holovsky, J.; Moon, S.-J.; Loeper, P.; Niesen, B.; Ledinsky, M.; Haug, F.-J.; Yum, J.-H.; Ballif, C. J. Phys. Chem. Lett., 5, 1035–1039 (2014).
[3] Ledinsky, M.; Schönfeldová, T.; Holovský, J.; Aydin, E.; Hájková, Z.; Landová, L.; Neyková, N.; Fejfar, A.; De Wolf, S. Temperature Dependence of the Urbach Energy in Lead Iodide Perovskites. J. Phys. Chem. Lett., 10, 1368–1373 (2019).
