Reducing the Excitonic Loss at Donor/Acceptor Heterojunction with Negligible Exciton Dissociation Driving Force

A breakthrough for non-fullerene acceptors (NFAs) is their efficient photocharge generation and low nonradiative voltage loss (ΔV_nrad) in a condition of negligible energy offset (ΔG_S1,CT) between the lowest singlet state (S₁) and the relaxed charge transfer (CT) state. This inspires the idea of viewing the donor/acceptor (D/A) binary blend as a single component in organic solar cells (OSCs) and attracts tremendous studies on the D/A pairs with negligible ΔG_S1,CT. Unfortunately, an arbitrarily chosen material combination usually results in severe photovoltaic performance loss. To solve this problem, we present a diffused heterojunction (DHJ) doping strategy at the D/A heterojunction with small ΔG_S1,CT. The electronic doping alleviates the performance loss by accelerating the exciton dissociation rate and reducing the ΔV_nrad. After examining the DHJ doping strategy in other six NFA material combinations, we are confident to point out that our work opens an avenue for pursuing intrinsic high OSC performance comparing with other single-component photovoltaic technologies.