From Carrier Generation to Collection: Unraveling the Origin of Composition Tolerance Differences in Polymer/NFA and All‐Polymer Solar Cells

Abstract A systematic study is conducted to compare the differences in charge dynamics and photovoltaic performances of organic photovoltaics fabricated with different donor:acceptor (D:A) blend ratios, employing a polymer donor, PBDB‐T, in combination with two distinct types of non‐fullerene acceptors Y6 and N2200. Device performance characterization reveals that the PBDB‐T:Y6 devices retain 3.32% and 45.10%, and the PBDB‐T:N2200 devices retain 38.17% and 23.24% of their respective peak efficiencies at extreme D:A ratios of 15:1 and 1:15, respectively, relative to the optimal 1:1 condition. Relevant results indicate that the PBDB‐T:Y6 system exhibits superior tolerance at high acceptor loadings, while the PBDB‐T:N2200 system demonstrates better tolerance under both donor‐rich and acceptor‐rich conditions. Additionally, relevant experiments show that the compositional tolerance is primarily determined by exciton dissociation and charge generation efficiency, rather than charge mobility and carrier recombination, highlighting that exciton dissociation and charge generation efficiency are closely related to the donor–acceptor interfacial area and govern device efficiency. Overall, this work fills a critical knowledge gap in understanding compositional tolerance mechanisms and provides theoretical guidance to promote the practical application of organic photovoltaics.