Inverted perovskite solar cells (PSCs) can deliver enhanced operating stability compared to their 'normal'-structure counterparts. To improve efficiency further, it is vital to combine effective light management with low interfacial losses. Now, scientists at Northwestern University, University of Kentucky, North Carolina State University, University of Toronto, Ecole Polytechnique Fédérale de Lausanne (EPFL) and Peking University have developed a conformal self-assembled monolayer (SAM) as the hole-selective contact on light-managing textured substrates.
The team reported that molecular dynamics simulations indicate cluster formation during phosphonic acid adsorption leads to incomplete SAM coverage. They devised a co-adsorbent strategy that disassembles high-order clusters, thus homogenizing the distribution of phosphonic acid molecules, thereby minimizing interfacial recombination and improving electronic structures.
The team reported a lab-measured power-conversion efficiency (PCE) of 25.3% and a certified quasi-steady-state PCE of 24.8% for inverted PSCs, with a photocurrent approaching 95% of the Shockley-Queisser maximum.
An encapsulated device with a PCE of 24.6% at room temperature retained 95% of its peak performance when stressed at 65°C and 50% relative humidity following >1000 hours of maximum power point tracking under 1-sun illumination.
This was said to represent one of the most stable PSCs subjected to accelerated ageing – achieved with a PCE surpassing 24%.
The engineering of phosphonic acid adsorption on textured substrates offers a promising avenue for efficient and stable PSCs. It is also anticipated to benefit other optoelectronic devices that require light management.
