Chinese researchers have developed high-entropy molecular contacts that enabled inverted perovskite solar cells to achieve a certified steady-state efficiency of 27.31%. The approach also improves thermal stability by preventing molecular contact degradation.
Improving power conversion efficiency and long-term operational stability remains a key challenge for perovskite solar cells, partly due to the thermal instability of conventional molecular contacts. Under thermal stress, single-component molecular contacts can lose their ordered molecular packing, compromising hole transport and accelerating device degradation. To address this issue, researchers in China have developed high-entropy molecular contacts (HE-MCs) designed to improve both device efficiency and operational stability.
“Developing high-entropy packing in hole-selective self-assembled molecule (HSM) systems to prevent molecular contact (MC) collapse remains unexplored,” the researchers said. “The key challenge is balancing ordered HSM self-assembly with high-entropy structural complexity while maintaining efficient hole transport.”
The researchers said their approach involves blending several specially designed HSMs with similar chemical structures but non-centrosymmetric units to promote complex molecular stacking. Mixing the molecules increases configurational disorder and enables the formation of HE-MCs at the hole-selective interface.
The group fabricated inverted perovskite solar cells using a molecular contact consisting of three related carbazole-based molecules: CbzNaph, CbzNaphBF and CbzNaphBT. The latter two incorporate oxygen- and sulfur-containing units, respectively, resulting in different intermolecular interactions and packing arrangements.
The researchers mixed the molecules at a 1:1:1 molar ratio, spin-coated the solution onto cleaned fluorine-doped tin oxide (FTO) glass substrates, and annealed it at 100 C for 10 minutes to form the hole-selective contact.
They then deposited a perovskite absorber with a bandgap of 1.55 eV using a two-step spin-coating process with chlorobenzene as an antisolvent, followed by annealing at 100 C for 30 minutes. After surface passivation, they deposited a 30 nm fullerene (C60) layer by thermal evaporation, a 40 nm tin oxide (SnO2) layer by atomic layer deposition, and a 100 nm copper rear electrode by thermal evaporation.
The researchers also applied a 120 nm magnesium fluoride coating to the back of the glass substrate to reduce reflection losses. The resulting cell featured an FTO/HE-MCs/perovskite/C60/SnO2/Cu architecture.
The team used molecular dynamics simulations, density functional theory calculations, and structural and spectroscopic measurements to investigate molecular packing and charge transport before and after thermal aging. It also evaluated the completed devices through efficiency measurements, prolonged exposure to 85 C, thermal cycling between room temperature and 85 C, and maximum power point tracking under continuous one-sun illumination at 85 C.
“The HE-MC-based devices showed improved average power conversion efficiency (PCE) from 26.37% to 27.29% compared with the CbzNaph-based device, accompanied by the enhanced open-circuit voltage (VOC) and fill factor (FF), which could be attributed to the enhanced hole-selectivity and interfacial passivation,” the researchers said.
The champion device achieved a power conversion efficiency of 27.50% under reverse-scan conditions, with an open-circuit voltage of 1.202 V, a short-circuit current density of 26.40 mA/cm2, and a fill factor of 86.67%. The researchers reported negligible hysteresis under forward-scan conditions.
The device also achieved an integrated short-circuit current density of 25.72 mA/cm2 based on external quantum efficiency measurements, in good agreement with the current density obtained from current-voltage measurements. The Tianjin Institute of Metrological Supervision and Testing independently certified a steady-state efficiency of 27.31% for one of the fabricated cells.
The certified result is slightly below the 27.41% efficiency reported in May 2026 for an inverted perovskite solar cell fabricated by researchers led by Shaanxi Normal University in China, in collaboration with Linköping University in Sweden and other institutions. The earlier result, published in nature, was certified under reverse-scan conditions.
The researchers presented their findings in “High-entropy molecular contacts enable high-efficiency and stable perovskite solar cells,” published in Nature Photonics. The research team included scientists from China’s City University of Hong Kong, Jilin University, and Sun Yat-sen University.
This content is protected by copyright and may not be reused. If you want to cooperate with us and would like to reuse some of our content, please contact: [email protected].