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Bifacial monolithic perovskite/silicon tandem solar cells exploit albedo—the diffuse reflected light from the environment—to increase their performance above that of monofacial perovskite/silicon tandems. Here we report bifacial tandems with certified power conversion efficiencies >25% under monofacial AM1.5G 1 sun illumination that reach power-generation densities as high as ~26 mW cm–2 under outdoor testing. We investigated the perovskite bandgap required to attain optimized current matching under a variety of realistic illumination and albedo conditions. We then compared the properties of these bifacial tandems exposed to different albedos and provide energy yield calculations for two locations with different environmental conditions. Finally, we present a comparison of outdoor test fields of monofacial and bifacial perovskite/silicon tandems to demonstrate the added value of tandem bifaciality for locations with albedos of practical relevance. Bifacial solar cells can outperform monofacial cells by exploiting sunlight reflected off the ground surface. De Bastiani et al. show that bifacial perovskite/silicon tandem with an optimized bandgap can deliver a power density of 26 mW cm–2 and compare its performance to monofacial cells under outdoor conditions.

Parasitic absorption in transparent electrodes is one of the main roadblocks to enabling power conversion efficiencies (PCEs) for perovskite‐based tandem solar cells beyond 30%. To reduce such losses and maximize light coupling, the broadband transparency of such electrodes should be improved, especially at the front of the device. Here, the excellent properties of Zr‐doped indium oxide (IZRO) transparent electrodes for such applications, with improved near‐infrared (NIR) response, compared to conventional tin‐doped indium oxide (ITO) electrodes, are shown. Optimized IZRO films feature a very high electron mobility (up to ≈77 cm2 V−1 s−1), enabling highly infrared transparent films with a very low sheet resistance (≈18 Ω □−1 for annealed 100 nm films). For devices, this translates in a parasitic absorption of only ≈5% for IZRO within the solar spectrum (250–2500 nm range), to be compared with ≈10% for commercial ITO. Fundamentally, it is found that the high conductivity of annealed IZRO films is directly linked to promoted crystallinity of the indium oxide (In2O3) films due to Zr‐doping. Overall, on a four‐terminal perovskite/silicon tandem device level, an absolute 3.5 mA cm−2 short‐circuit current improvement in silicon bottom cells is obtained by replacing commercial ITO electrodes with IZRO, resulting in improving the PCE from 23.3% to 26.2%.

Ion implantation and laser processing technologies are very attractive for the fabrication of industrially feasible interdigitated back-contact (IBC) solar cells. In this work, p + emitters were fabricated by boron implantation and laser annealing, and the electrical properties of emitters were investigated. An emitter sheet resistance ( R sh ) in the range of 30-200 Ω/□ could be achieved by varying the implanted dose. The saturation current density ( J oe ) of the passivated p + emitter with R sh of ∼125 Ω/□ reached 95 fA/cm 2 , and the contact resistivity was determined to be as low as 5×10 -6 Ω·cm 2 . Such localized p + emitters can be applied to n-type IBC solar cells, which could avoid the high temperature thermal annealing step and related problems.

Laser doping of crystalline silicon has been the subject of intense research over the past decade, due to its potential to enable the fabrication of high efficiency and low-cost crystalline silicon solar cells. Information regarding the doping profile created by the process is critical for process optimisation, however is generally difficult to obtain. In this paper, a relatively new technique for characterising laser doping cross-sections — Secondary Electron Microscopy Dopant Contrast Image (SEMDCI) — is compared with the widely used Electron Beam Induced Current (EBIC) method. A good agreement between the two techniques regarding the p-n junction profile is demonstrated. The differences between the methods are attributed to the difference of the sensitivity. The comparison demonstrates the reliability and usefulness of the SEMDCI as a characterisation method for laser doping, which shows both the p-n junction outline and dopant distribution within the doped regions. The differences between the methods and the challenges associated with the application of the SEMDCI method are also discussed.

In this paper, the impact of the N2 anneal on laser processed silicon was investigated using photoluminescence (PL) imaging through comparing the PL signal of laser processed samples before and after N2 anneal. The samples capped with different dielectrics or without any dielectric (bare surface) prior to the laser processing were used, enabling the evaluation of the influence of the N2 anneal on the defects caused both by laser thermal effect and by the existence of dielectrics. Generally, it was found that N2 anneal is an effective way to reduce both the laser and dielectric induced defects.