CsPbI₂Br-based perovskite solar cells (PSCs) have attracted much attention because of their excellent phase stability and appropriate bandgap. However, numerous defects of undercoordinated ions or mobile species are the sites of carrier nonradiative recombination, causing a low power conversion efficiency (PCE). In this work, NaCl and nitrogen-doped graphene quantum dots (N-GQDs) as binary additives are introduced into perovskite precursor to obtain high-quality photoactive films. Chloride ion (Cl⁻) is incorporated into perovskite due to the same physical and chemical properties as bromine (Br⁻), that align the energy level of CsPbI₂Br, decrease the energy barrier between perovskite and P3HT to promote carrier transport and extraction, hence result in the reduced energy loss. Meanwhile, because of its good conductivity, N-GQDs at grain boundaries can rapidly conduct photogenerated electrons to SnO₂, suppressing carrier recombination at grain boundaries. Furthermore, the trap state density of the CsPbI₂Br film with binary additives is reduced, which could prolong the carrier lifetime, and improve surface morphology. As a result, a PCE of 15.37% for CsPbI₂Br PSCs with binary additives is obtained，which shows ∼22.76% relative increment compare with the pristine PSCs. Therefore, a simple and convenient optimization strategy of binary additives for PSCs is proposed in this work.

Introducing additives into perovskite layers is an effective method to enhance the power conversion efficiency (PCE) and operation stability of perovskite solar cells (PSCs). Herein, we reported an addition of carbon nanodots (CNDs) into the CsPbI₂Br photoactive layer to boost performance of the related PSCs. It is found that the trap density can be notably suppressed, and the crystallinity can be enhanced after introducing CNDs with an optimal quantity. The PSC with 1.0 wt% addition of CNDs delivers a notable improved average PCE of 13.77% (the highest PCE: 14.69%) from that of 12.14% for the control device without CND addition. Moreover, the CND-added CsPbI₂Br PSCs exhibit superior stability, i.e., ∼86 % retention of the initial PCE after 160 h aging in air with the humidity of 20%–30%, to the control device.