Synergistic regulation of defects, charge carriers, and ions via bimolecular engineering in carbon-based perovskite photovoltaics

Printable carbon-based perovskite solar cells (C-PSCs) offer a pathway to scalable, low-cost solar energy production, thanks to their built-in stability and fully printable fabrication that avoids expensive metals and vacuum processes. However, their commercial potential is limited by high levels of nonradiative recombination at the perovskite/hole transport layer (HTL) interface, which sharply lowers device efficiency. Traditional two-dimensional (2D) passivators, like octylammonium iodide (OAI), reduce surface defects by forming protective layers, but the large alkylammonium groups create steric barriers that block efficient vertical hole transport and increase charge accumulation. To address this trade-off, we introduce a bimolecular interlayer combining OAI and (2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl)phosphonic acid (MeO-2PACz). OAI forms 2D layers to fill ionic vacancies, while MeO-2PACz binds to exposed Pb 2+ sites, passivating multi-site defects and strengthening the crystal structure. The resulting self-assembled OAI/MeO-2PACz (OMZ) layer creates energy gradients and aligns Fermi levels, enhancing hole extraction and suppressing recombination losses. This strategy achieves a record 23.15% efficiency in low-temperature-printed C-PSCs and enables semitransparent modules (10 cm 2 ) with 18.77% efficiency. Encapsulated devices retain 95% of initial performance after 1,000 h of maximum power point tracking, with outdoor tests confirming long-term stability under real-world conditions. By balancing defect passivation, charge transport, and ion management through simple molecular engineering, this work paves the way for robust, printable C-PSC at industrial scale, advancing affordable and reliable solar power for widespread adoption. • Synergistic defect management by OAI and MeO-2PACz suppresses nonradiative loss • MeO-2PACz counteracts OAI-induced n-type shift via dipole engineering • Iodide diffusion barrier raised to Δ E > 1.1 eV for superior stability • Record efficiencies of 23.15% (cell) and 18.77% (semitransparent module) achieved Synergistic defect management by OAI and MeO-2PACz suppresses nonradiative loss MeO-2PACz counteracts OAI-induced n-type shift via dipole engineering Iodide diffusion barrier raised to Δ E > 1.1 eV for superior stability Record efficiencies of 23.15% (cell) and 18.77% (semitransparent module) achieved Low-temperature-printed carbon-based perovskite solar cells (C-PSCs) hold great promise for commercialization, yet their power conversion efficiency (PCE) remains constrained by interfacial nonradiative recombination. Conventional two-dimensional (2D) passivation partially mitigates defects but sterically hinders vertical charge transport. Here, we developed a bimolecular interlayer integrating octylammonium iodide (OAI) and (2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl) phosphonic acid (MeO-2PACz) to synergistically manage defects, carriers, and ions. OAI-derived 2D perovskites heal A-/X-site vacancies, while MeO-2PACz forms Pb-O-P bonds to passivate B-site defects, enhancing hole-selective contacts and inducing upward band bending. The architecture also elevates the ion diffusion barrier to 1.12 eV, effectively suppressing ion migration. This approach achieves a record PCE of 23.15% for n-i-p C-PSCs and 18.77% per active area for 10 cm 2 semitransparent (35.8% visible light transmittance) carbon-based perovskite solar modules (C-PSMs). Remarkably, C-PSMs retain 95% of initial PCE after 1,000 h of maximum power point tracking, with outdoor tests confirming silicon-comparable performance.