For years, the race to make better perovskite solar cells was a race about the light-absorbing layer itself: tweak the crystal, widen the bandgap, add a passivating additive. A new paper suggests the decisive frontier has moved to something almost absurdly thin: a single molecular carpet, roughly a thousandth of the wavelength of visible light, that sits between the perovskite and the electrode. Engineering that carpet lifted certified efficiency above 27 percent and, more strikingly, transformed how long the cells hold up under continuous illumination. The work, published in Nature Communications, comes from a team led by Chongqing University, with collaborators in Japan and Hong Kong.
Perovskite solar cells are built like sandwiches: a light-absorbing perovskite crystal between an electron-collecting layer and a hole-collecting layer. The fastest-improving configuration, called inverted or p-i-n, collects holes at the bottom electrode, and it is prized for its durability and its compatibility with tandem cells, in which a perovskite sits atop a silicon cell. Its hole-transport layer is increasingly made of self-assembled monolayers, SAMs: small molecules with three parts, a phosphonic acid anchor that bonds to the metal-oxide surface, a linker, and a terminal group that sets the energy landscape and touches the perovskite. SAMs are cheap, thin, and transparent, but they have a known weakness. They tend to clump together, they wet surfaces unevenly, and their interaction with the perovskite is often weak, which creates energy losses at the buried interface, the boundary where the perovskite meets the transport layer. Those losses cost voltage, and voltage is where modern cells win or lose.
The team, with Yi Pan, Lei Liu, Haoxuan Guo, and Changqin Lin as co-first authors and Kuan Sun, Qiang Liao, and colleagues as corresponding authors, started from the workhorse molecule 2PACz, a carbazole-based SAM, and added a 3,5-dimethoxyphenyl group to its terminal end, producing a new molecule they call DMPA. The addition is small in scale and large in effect. The two methoxy groups carry electron-rich oxygen atoms that bond chemically to the perovskite above and strengthen anchoring to the nickel oxide surface below. Calculations showed DMPA has the strongest adsorption energy of the molecules tested, -2.67 electron volts on the oxide, and molecular dynamics simulations showed it suppresses its own clumping, packing more densely (6.8 x 10^13 molecules per square centimeter versus 4.5 x 10^13 for the standard layer) and nearly doubling hole mobility.
The electrical payoff is a champion power conversion efficiency of 27.59 percent, independently certified at 27.2 percent by China’s National Institute of Measurement and Testing Technology, with reduced nonradiative recombination at the interface (the light-intensity slope fell from 1.66 to 1.21 kT/q). But the durability numbers are arguably the bigger story. Under the ISOS-L-2 protocol, encapsulated cells held at 65 °C under one-sun white-LED illumination with maximum power point tracking retained 94.5 percent of their initial efficiency after 1,600 hours. The standard 2PACz control retained 66.9 percent; the non-methoxy analog BCPA retained 86.4 percent. Even unencapsulated storage in nitrogen showed the pattern: 95.9 percent retention after 2,000 hours for DMPA, versus 72.7 percent for the control.
The contrast with the control is the clearest demonstration that the interface, not the absorber, is where stability is being won. SAM-based devices were long suspected of failing at the buried interface, where weak molecular contact lets defects and strain accumulate. A molecule that chemically bridges both sides of that boundary addresses the failure directly.
Context matters for reading the numbers. The certified 27.2 percent places DMPA-based cells among the top single-junction inverted devices, a category that has climbed rapidly in the past two years; tandem cells, which stack two absorbers, have already reached certified efficiencies above 31 percent, including a large-area evaporated perovskite-silicon tandem reported earlier this month. The significance of this paper is the toolkit, not the headline: a terminal-group design rule (add electron-rich groups that bond the interface) that other groups can apply to their own molecules.
The caveats are standard for the field and worth stating. The champion cells are laboratory-scale, not modules. The stability tests run under nitrogen with encapsulation, a controlled condition that does not replicate outdoor weather, and 65 °C is warm but below the 85 °C automotive durability standard some applications demand. Certification came from a single institution. And the manuscript is an early-access version, published in unedited form before final copyediting.
Still, the direction of the field is visible in this work: as the absorber approaches its theoretical limits, the volts are leaking at the seams, the molecular seams between layers. The team’s answer, a molecule that holds hands with both sides of the interface, is a reminder that at the nanometer scale, chemistry is the ultimate engineering material.
Sources: Pan, Y., Liu, L., Guo, H. et al. Self-assembled multilayers reduce interfacial energy loss in perovskite solar cells. Nature Communications (2026). DOI: 10.1038/s41467-026-76497-1.