3,5-Dinitrobenzoic Acid Enables Stable and Efficient HTL-Free MAPbI₃ Perovskite Solar Cells

Hybrid perovskite solar cells have gained interest for their high solar energy efficiency and low-temperature solution processing properties. However, severe surface defects at perovskite grain boundaries still hinder improvements in device efficiency and performance. Here, we effectively introduced organic compound 3,5-dinitrobenzoic acid (DNBZ) as an additive to the perovskite solution. The DNBZ additive containing a benzene ring and carboxyl (-COOH) and nitro (-NO₂) functional groups effectively reacts with uncoordinated lead ions (Pb²⁺) to reduce defects/traps in perovskite films, improving their film quality, minimizing nonradiative recombination, and enhancing charge transportation and the efficiency of CPSCs. Furthermore, the hydrophobic properties of the benzene ring limit the perovskite's interaction with water, improving the moisture stability of CPSCs. Interestingly, 1 mg-DNBZ added carbon counter electrode-based HTL-free MAPbI₃ perovskite solar cells (CPSCs) have a power conversion efficiency (PCE) enhanced from 8.36 to 10.11%. Furthermore, after being kept for 22 days, the PCE of CPSCs treated with 1 mg-DNBZ can retain 87% of its initial PCE (under the condition of 30 °C and RH = 50 ± 5%), indicating a significant improvement in long-term durability. Our investigations reveal that the DNBZ additive strategy improves the stability, efficiency, performance, and quality of perovskite films. The present work provides a straightforward method to fabricate inexpensive and highly efficient CPSCs.