Next-generation photovoltaics (PV) systems provide key opportunities for manufacture and commercialization. Hybrid lead halide perovskite solar cells (PSCs) represent an attractive system as they combine high efficiency with inexpensive, abundant materials and low-temperature and solution-based processing methods. Among the various perovskite solar cell architectures, the carbon-based, triple-stack perovskite solar cell (C-PSC) is a promising candidate for upscaling and commercialization, employing a fully printable architecture, and allowing manufacture at low capital cost using screen-printing technology.

One of the most attractive aspects of this technology is its inherent better stability against moisture related to the hydrophobic character of the carbon top layer [1]. However, until recently [2] the record efficiency has been much lower that conventional PSCs, specifically due to a much lower open circuit photovoltage and generally lower fill factor. Several reasons include the non-selectivity of the carbon top layer, interface recombination related to the nanostructured morphology, and the complexity of infiltration of optimized perovskite precursors.

In our group, we are performing research on several aspects of materials design, device optimization and scale-up: (i) design and synthesis of new materials based on green chemistry principles to improve sustainability; (ii) enhancing performance by implementation of improvement strategies, included interfacial modifications at both the electron and hole extraction contacts; (iii) advanced characterization methods including impedance spectroscopy and light intensity-modulated photocurrent and photovoltage spectroscopy (IMPS/IMVS), and optimization strategies using machine learning; (iv) up-scaling to mini-module size (200 cm²); and (v) long-term module monitoring under outdoor conditions.

In this presentation, four aspects of recent work will be presented: (i) effect of humidity on the performance of the TiO₂ electron extraction layer using anatase, brookite and rutile-based solar cells [3]; (ii) increase of the solar cell efficiency by incorporating a hole-selective NiCo₂O₄ printed layer between the zirconia and (non-selective) carbon layer [4]; and (iii) analysis of solar module performance under harsh, tropical outdoor conditions as a function of climatological parameters (manuscript submitted).