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Organic photovoltaics based on non-fullerene acceptors (NFAs) show record efficiency of 16 to 17% and increased photovoltage owing to the low driving force for interfacial charge-transfer. However, the low driving force potentially slows down charge generation, leading to a tradeoff between voltage and current. Here, we disentangle the intrinsic charge-transfer rates from morphology-dependent exciton diffusion for a series of polymer:NFA systems. Moreover, we establish the influence of the interfacial energetics on the electron and hole transfer rates separately. We demonstrate that charge-transfer timescales remain at a few hundred femtoseconds even at near-zero driving force, which is consistent with the rates predicted by Marcus theory in the normal region, at moderate electronic coupling and at low re-organization energy. Thus, in the design of highly efficient devices, the energy offset at the donor:acceptor interface can be minimized without jeopardizing the charge-transfer rate and without concerns about a current-voltage tradeoff.
Comparative literature on institutional reforms in multi-level systems proceeds from a global trend towards the decentralization of state functions. However, there is only scarce knowledge about the impact that decentralization has had, in particular, upon the sub-central governments involved. How does it affect regional and local governments? Do these reforms also have unintended outcomes on the sub-central level and how can this be explained? This article aims to develop a conceptual framework to assess the impacts of decentralization on the sub-central level from a comparative and policyoriented perspective. This framework is intended to outline the major patterns and models of decentralization and the theoretical assumptions regarding de-/re-centralization impacts, as well as pertinent cross-country approaches meant to evaluate and compare institutional reforms. It will also serve as an analytical guideline and a structural basis for all the country-related articles in this Special Issue.