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Random terpolymerization is an effective approach to achieving highly efficient and outdoor-stable terpolymer photovoltaics. However, the working principle behind this remains unclear. Herein, we report spectroscopic, morphological, and computational results and conclude the previous work on terpolymer research to unveil their structure–property relations and elucidate key rules for high-efficiency and outdoor-stable terpolymer photovoltaics. More specifically, introducing a strong electron-deficient or electron-rich third moiety is suggested to enable broadened absorption with minimized non-radiative voltage losses. Besides, the third component should manipulate the D/A miscibility towards a thermodynamically more stable morphology. However, the content of the third component should be small to maintain molecular orientation and exciton diffusion length in conjunction with optimized phase-separation and crystallinity, in turn reducing bimolecular carrier recombination. Obeying these rules, terpolymer solar cells based on the parent donors D18 and PM6 with enhanced power conversion efficiency (PCE) and excellent outdoor stability are demonstrated. Our findings provide a rationale for explaining and achieving high-performance and outdoor-stable terpolymer photovoltaics, paving the path to commercialization.

Non-fullerene acceptor (NFA)-based ternary bulk heterojunction solar cells (TSC) are the most efficient organic solar cells (OSCs) today due to their broader absorption and quantum efficiencies (QE) often surpassing those of corresponding binary blends. We study how the energetics driving charge transfer at the electron donor:electron acceptor (D/A) interfaces impact the QE in blends of PBDB-T-2F donor with several pairs of lower bandgap NFAs. As in binary blends, the ionization energy offset between donor and acceptor ({\Delta}IE) controls the QE and maximizes for {\Delta}IE > 0.5 eV. However, {\Delta}IE is not controlled by the individual NFAs IEs but by their average, weighted for their blending ratio. Using this property, we improved the QE of a PBDB-T-2F:IEICO binary blend that had an insufficient {\Delta}IE for charge generation by adding a deep IE third component: IT-4F. Combining two NFAs enables to optimize the D/A energy alignment and cells' QE without molecular engineering., Comment: S Karuthedath and S H K Paleti contributed equally. MS: 35 pages, 9 figures. SI: 21 pages, 23 figures - updates: added a model scheme as Fig1, updated T1 EQE and blends PL in Fig 2 (former 1). Added Figure (5): charge generation upon acceptor excitation. Corrected {\Delta}IEs in fig7 and 9 (a few tens of meV off). Added more blends to show generality (2 groups, 10 blends compositions)

Solution-processed metal halide perovskite (MHP) single crystals (SCs) are in high demand for a growing number of printed electronic applications due to their superior optoelectronic properties compared to polycrystalline thin films. There is an urgent need to make SC fabrication facile, scalable, and compatible with the printed electronic manufacturing infrastructure. Here, a universal cosolvent evaporation (CSE) strategy is presented by which perovskite SCs and arrays are produced directly on substrates via printing and coating methods within minutes at room temperature from drying droplets. The CSE strategy successfully guides the supersaturation via controlled drying of droplets to suppress all crystallization pathways but one, and is shown to produce SCs of a wide variety of 3D, 2D, and mixed-cation/halide perovskites with consistency. This approach works with commonly used precursors and solvents, making it universal. Importantly, the SC consumes the precursor in the droplet, which enables the large-scale fabrication of SC arrays with minimal residue. Direct on-chip fabrication of 3D and 2D perovskite photodetector devices with outstanding performance is demonstrated. The approach shows that any MHP SC can now be manufactured on substrates using precision printing and scalable, high-throughput coating methods.

This work was supported by the Australian Government through the Australian Renewable Energy Agency (ARENA) and the Australian Research Council. Responsibility for the views, information or advice expressed herein is not accepted by the Australian Government. J.P. acknowledges the funding support from Australian Nanotechnology Network (ANN) and Department of Innovation, Industry, Science and Research (DIISR). The research reported in this publication was supported by funding from King Abdullah University of Science and Technology (KAUST). The authors thank Xavier Pita, scientific illustrator at King Abdullah University of Science and Technology (KAUST), for producing Figure 1a in this paper. J.P. conceived the idea, designed the overall experiments, and led the project. J.P., T.D., H.S., and Y.W. prepared and characterized the perovskite cell devices. J.I.K. and E.U. performed the TA and TRPL measurements and data analysis. F.L. supervised the TA and TRPL measurements and analysis. W.L., X.Y., and J. P. conducted the FTIR measurements and analysis. W.L. performed the DFT calculation. T.D., H.S., and Y.W. conducted the PL imaging measurements. H.D. conducted the XRD and SEM measurements. K.W. conducted the NMR measurements and analysis. E.A. conducted the EQE measurements. J.P., J.I.K., K.J.W., K.R.C., F.L., S.D.W., and T.P.W. contributed to the results analysis and interpretation. T.P.W. and S.D.W. supervised the project. J.P. wrote the manuscript. All authors contributed to the discussion of the results and revision of the manuscript.