Publication date: 18th August 2023
Hybrid perovskite solar cells (PSCs) are one of the most promising technologies for new-generation photovoltaics due to outstanding semiconductor properties and low-cost solution processing methods for the fabrication. Indeed, PSCs dominated the PV scientific research in the last decade, by developing efficient and stable devices, produced by employing scalable and low-cost printing techniques, easily embedded in roll2roll or sheet2sheet production lines. Moreover, perovskite (PSK) PV has been recently demonstrate to work in synergy with the silicon solar cells by achieving astonishing power conversion efficiency (PCE) above 33% on small area perovskite/silicon (PSK/Si) tandem solar cells, making such new PV technology appealing for the market.[1] However, PSK/Si tandem technology still requires to demonstrate the transfer from lab to fab, pushing the scientific community in finding brilliant solutions for drawing a feasible and reliable route toward its commercialization. In this scenario, the scaling of device dimensions still requires efforts for the perovskite scientific community, since, as soon as the device active area increases, PCE undergoes a not-negligible drop due to i) the not-trivial control of the perovskite crystal quality over large area substrate, ii) the increasing impact of non-radiative charge recombination mechanisms at the interfaces, iii) the not optimized layout for the semi-transparent perovskite top device, iv) a not-proper choice of the final architecture for the large area PSK/Si panel. Moreover, without an ad-hoc developed encapsulation and lamination procedure, tandem device cannot overcome the stability tests established for a marketable PV technology. In this scenario, the use of interface engineering [2] based on bi-dimensional (2D) materials is here proposed as an efficient tool for trap passivation and energy level alignment in perovskite top devices, by mitigating the performance losses induced by the scaling-up process.[3] In particular, in this work, the successful application of 2D materials, i.e., graphene in the electron transporting layer (ETL),[4,5] MXenes [6,7] in perovskite absorber and a 2D perovskite over-layer, together with a careful optimization of the module layout, allowed to achieve PCE overcoming 16% on 90 cm2 (substrate area) semi-transparent perovskite module. Several characterization techniques have been employed to elucidate the role of each 2D material in the final device optimization, such as photoluminescence (PL) spectroscopy,[8] transient PL (both at room temperature or at 11 K),[9] ultraviolet photoemission spectroscopy (UPS),[10] transient absorbtion spectroscopy (TAS) [11] etc. The as-optimized PSK modules have been coupled with wafer sized (15.7x15.7 cm2) silicon heterojunction (Si-HJT) bifacial cells produced by 3 Sun company, in a novel panel architecture called two-terminal (2T) voltage-matched (VM) architecture.
Following this approach, on one side the perovskite solar modules can be independently optimized, realized and stacked atop the commercial Si-HJT cells employing an ad-hoc developed lamination process. On the other side, the as-proposed panel architecture does not require any modification in the Si production lines, making the tandem technology appealing for the already exiting Si cell producers. Moreover, among the advantages of the VM architecture, the much less sensitivity toward spectral variations allowed to employ bifacial Si-HJT bottom cell, gaining extra power output exploiting the radiation reflected by the ground (albedo).[12]