Printing a 30% solar cell
Perovskite-silicon tandem solar cells are the leading candidate to push panels past the limits of silicon alone, but many record cells are made with lab-scale methods that do not translate easily to factories. According to TaiyangNews, researchers at Germany’s Karlsruhe Institute of Technology (KIT) have now demonstrated a perovskite-silicon tandem cell with 30.2% efficiency using a process built around inkjet printing, which they describe as the first time such a cell has passed 30% with an inkjet-based perovskite absorber.
How the cell is made
The route is a hybrid, two-step one. First, a self-assembled monolayer that serves as the hole-transport layer is applied by dip-coating: 2PACz on the substrate for perovskite-only cells, and Ph4PACz on the silicon surface for tandems. The perovskite absorber is then formed in two stages. Inorganic precursors are deposited by thermal evaporation, and the organic precursors are inkjet printed on top. A passivation layer is finally added by dip-coating.
These processes were combined with textured silicon heterojunction bottom cells to build monolithic tandems, using a wide-bandgap perovskite top cell. Texturing the silicon is how commercial cells trap light, so working on a textured surface is a step toward industrial relevance.
The results
The champion tandem reached a power-conversion efficiency of 30.2%, with an open-circuit voltage of 1.94 V, a short-circuit current density of 20.4 mA/cm2 and a fill factor of 75.8%. It held above 30% during 10 minutes of maximum power point tracking, a short test that shows stability only over minutes, not years.
To probe scaling, the team also made a single-junction perovskite mini-module with a 12.96 cm2 active area, nine series-connected stripes of 1.44 cm2 each formed by laser scribing. It reached 17.8% efficiency. Compared with the median of the smaller cells, the loss was 0.53 percentage points per decade of area scaling, a useful number for judging how well a process survives larger sizes.
What is still unfinished
The fill factor of 75.8% is modest. The researchers attribute it to a tandem architecture that is not yet optimized on textured silicon. Better laser-scribing precision and tighter process control, they say, will matter for turning the laboratory process into a manufacturing route. No commercial timeline appears in the source, and the page reports no long-term stability or outdoor data.
Practical takeaways
- Inkjet printing plus dip-coating is a scalable-looking route to high-efficiency tandems.
- 30.2% is a small-cell result; the 17.8% mini-module shows the gap that scale-up must close.
- Fill factor is the clearest room for improvement.
- Ten minutes of tracking is not a durability result.
Bottom line
KIT’s result is less about a new efficiency record and more about method: showing that printing-based deposition can reach the 30% club. If scaling losses stay as low as the 0.53-point-per-decade figure suggests, manufacturers get a credible path from lab cell to production line.