Kylie Catchpole1

1, Australian National University, Acton, Australian Capital Territory, Australia

Combining perovskites with silicon is a particularly attractive option for producing cheap, high efficiency and high voltage solar cells. Perovskite-on-silicon tandem solar cells can potentially achieve over 30% tandem efficiency, which greatly surpasses the current record of 25.6% for the single silicon cell.

We demonstrate a 4-terminal tandem configuration in which the efficiency is as high as 26%, which is the highest efficiency that has been achieved with a potentially low cost process [1]. We also demonstrate a two-terminal monolithic tandem device with a perovskite top subcell and a high-temperature tolerant homojunction c-Si bottom subcell, with an efficiency of over 22% [2]. Several developments have been instrumental in achieving these high efficiencies. The first is development of a combined grid/transparent conducting oxide back contact for the top subcell of 4-terminal tandems, which allows over 80% of long wavelength light to pass through to the silicon solar cell underneath [3]. Incorporation of rubidium in a multi-cation perovskite improves both efficiency and stability [4]. Doping the compact TiO2 layer with indium also improves conductivity and band alignment [5]. Finally we have also found that a combination of PMMA and PCBM can provide effective interface passivation for perovskite solar cells [6]. These results show the clear potential of perovskites in practical high efficiency tandem devices.

[1] The Duong et al, Rubidium Multication Perovskite with Optimized Bandgap for Perovskite-Silicon Tandem with over 26% Efficiency, Advanced Energy Materials, 7, 14, 1700228 (2017).
[2] Yiliang Wu et al., Monolithic perovskite/silicon-homojunction tandem solar cell with over 22% efficiency, Energy and Environmental Science, in press (2017).
[3] The Duong et al, Semi-transparent perovskite solar cell with sputtered front and rear electrodes for a four-terminal tandem, IEEE Journal of Photovoltaics 6 (3), 679-687 (2016).
[4] The Duong et al, Structural engineering using rubidium iodide as a dopant under excess lead iodide conditions for high efficiency and stable perovskites, Nano Energy, 30, 330 (2016).
[4] Jun Peng et al, Interface engineering of high performance perovskite solar cells and perovskite-silicon tandems, Advanced Energy Materials, 10.1002/aenm.201601768 (2016).
[6] Jun Peng et al, Interface passivation using ultrathin polymer-fullerene films for high-efficiency perovskite solar cells with negligible hysteresis, Energy and Environmental Science, DOI: 10.1039/C7EE01096F (2017).