Rubidium (Rb) is explored as an alternative cation to use in a novel multication method with the formamidinium/methylammonium/cesium (Cs) system to obtain 1.73 eV bangap perovskite cells with negligible hysteresis and steady state efficiency as high as 17.4%. The study shows the beneficial effect of Rb in improving the crystallinity and suppressing defect migration in the perovskite material. The light stability of the cells examined under continuous illumination of 12 h is improved upon the addition of Cs and Rb. After several cycles of 12 h light–dark, the cell retains 90% of its initial efficiency. In parallel, sputtered transparent conducting oxide thin films are developed to be used as both rear and front transparent contacts on quartz substrate with less than 5% parasitic absorption of near infrared wavelengths. Using these developments, semi‐transparent perovskite cells are fabricated with steady state efficiency of up to 16.0% and excellent average transparency of ≈84% between 720 and 1100 nm. In a tandem configuration using a 23.9% silicon cell, 26.4% efficiency (10.4% from the silicon cell) in a mechanically stacked tandem configuration is demonstrated which is very close to the current record for a single junction silicon cell of 26.6%.

The interdigitated back contact (IBC) solar cells developed at the Australian National University have resulted in an independently confirmed (Fraunhofer Institut für Solare Energiesysteme (ISE) CalLab) designated‐area efficiency of 24.4 ± 0.7%, featuring short‐circuit current density of 41.95 mA/cm2, open‐circuit voltage of 703 mV and 82.7% fill factor. The cell, 2 × 2 cm2 in area, was fabricated on a 230 µm thick 1.5 Ω cm n‐type Czochralski wafer, utilising plasma‐enhanced chemical vapour deposition (CVD) SiNx front‐surface passivation without front‐surface diffusion, rear‐side thermal oxide/low‐pressure CVD Si3N4 passivation stack and evaporated aluminium contacts with a finger‐to‐finger pitch of 500 µm. This paper describes the design and fabrication of lab‐scale high‐efficiency IBC cells. Characterisation of optical and electronic properties of the best produced cell is made, with subsequent incorporation into 3D device modelling used to accurately quantify all losses. Loss analysis demonstrates that bulk and emitter recombination, bulk resistive and optical losses are dominant and suggests a clear route to efficiency values in excess of 25%. Additionally, laser processing is explored as a means to simplify the manufacture of IBC cells, with a confirmed efficiency value of 23.5% recorded for cells fabricated using damage‐free deep UV laser ablation for contact formation. Meanwhile all‐laser‐doped cells, where every doping and patterning step is performed by lasers, are demonstrated with a preliminary result of 19.1% conversion efficiency recorded. Copyright © 2014 John Wiley & Sons, Ltd.

In this study we make a detailed comparison between indium tin oxide (ITO), aluminum-doped zinc oxide (ZnO:Al) and hydrogenated indium oxide (IO:H) when applied on the illuminated side of rear-junction silicon heterojunction (SHJ) solar cells. ITO being the state of the art material for this application, ZnO:Al being an attractive substitute due to its cost effectiveness and IO:H being a transparent conductive oxide (TCO) with high-mobility and excellent optical properties. Through numerical simulations, the optically optimal thicknesses for a double layer anti-reflective coating system, consisting of the respective TCO and amorphous silicon oxide (a-SiO2) capping layers are defined. Through two-dimensional electrical simulations, we present a comparison between front-junction and rear-junction devices to show the behavior of series resistance (Rs) in dependence of the TCO sheet resistance (Rsh) and the device effective lifetime (τeff). The study indicates that there is a τeff dependent critical TCO Rsh value, above which, the rear-junction device will become advantageous over the front-junction design in terms of Rs. Solar cells with the respective layers are analyzed. We show that a thinner TCO optimized layer will result in a benefit in cell performance when implementing a double layer anti-reflective coating. We conclude that for a highest efficiency solar cell performance, a high mobility TCO, like IO:H, is required as the device simulations show. However, the rear-junction solar cell design permits the implementation of a lower conductive TCO in the example of the cost-effective ZnO:Al with comparable performance to the ITO, opening the possibility for substitution in mass production.

We report the fabrication and characterization of TiO2 sol–gel diffraction gratings on silicon substrates by using nanoimprint lithography. The gratings are homogeneous and free of defects and cover an area of 25 cm2. Minority carrier lifetimes of up to 900 µs for imprinted samples under illumination are reported, which Kelvin probe measurements indicate is due to light‐generated negative charge in the films. The structures reported here are very promising as light‐trapping, passivating coatings for solar cells. Copyright © 2011 John Wiley & Sons, Ltd.

In this article, we report on the properties of indium 6 tin oxide (ITO) deposited on thin-film silicon layers designed for the 7 application as carrier selective contacts for silicon heterojunction 8 (SHJ) solar cells. We find that ITO deposited on hydrogenated 9 nanocrystalline silicon (nc-Si:H) layers presents a significant drop 10 on electron mobility µ e in comparison to layers deposited on 11 hydrogenated amorphous silicon films (a-Si:H). The nc-Si:H layers 12 are not only found to exhibit a larger crystallinity than a-Si:H, 13 but are also characterized by a considerably increased surface rms 14 roughness. As we can see from transmission electron microscopy, 15 this promotes the growth of smaller and fractured features in the 16 initial stages of ITO growth. Furthermore, secondary ion mass 17 spectrometry profiles show different penetration depths of hydro-18 gen from the thin film silicon layers into the ITO, which might both 19 influence ITO and device passivation properties. Comparing ITO to 20 aluminum doped zinc oxide (AZO), we find that AZO can actually 21 exhibit superior properties on nc-Si:H layers. We assess the impact 22 of the modified ITO R sh on the series resistance R s of SHJ solar 23 cells with >23% efficiency for optimized devices. This behavior 24 should be considered when designing solar cells with amorphous 25 or nanocrystalline layers as carrier selective contacts. 26 Index Terms-Aluminum doped zinc oxide (AZO), indium tin 27 oxide (ITO), secondary ion mass spectrometry (SIMS), series 28 resistance, silicon heterojunction (SHJ), transmission electron 29 microscopy (TEM), transparent conductive oxide (TCO).