Prof Henry Snaith FRS

Abstract:

This 6th annual Emerging PV Report surveys peer‐reviewed advances since August 2024 across perovskite, organic, kesterite, matildite, antimony seleno‐sulfide, selenium, and tandem solar cell architectures. Updated graphs, tables, and analyses compile the best‐performing devices from the emerging‐pv.org database, benchmarking power conversion efficiency (PCE), flexible photovoltaic fatigue factor (F), light‐utilization efficiency (LUE), and stability‐test energy yield (STEY) against detailed‐balance efficiency limits as functions of photovoltaic bandgap, and average visible transmittance (AVT) for (semi‐)transparent devices. Beyond efficiency, operational stability is assessed via degradation rates (DR) and t95 lifetimes. Highlights include single‐junction perovskite cells with efficiencies above 27%, organics surpassing 20%, and new Si/perovskite tandems exceeding 34%. Although multiple record efficiencies have been achieved this year, advances in mechanical robustness and operational stability remain inconsistent, especially in complex tandem stacks, emphasizing the urgent need for standardized protocols, improved large‐area homogeneity, and database‐driven benchmarks to accelerate the transition from laboratory demonstrations to scalable, real‐world deployment.

Abstract:

Colloidal quantum dots (CQDs) are promising materials for constructing ‘second-window’ near-infrared (1000–1700 nm) light-emitting diodes (NIR-II LEDs), but their practical application has been hampered by low film external quantum efficiency (EQE). Here, we report a chemical strategy that incorporates photoactive fluorophores—spanning fluorescence, phosphorescence and thermally activated delayed fluorescence—into CQD films to boost NIR-II emission. Energy transfer from fluorophores (via both singlet and triplet pathways) raises the photoluminescence quantum efficiency of CQD to 85% beyond 1000 nm. As a result, these composite films power NIR-II LEDs with a record EQE of 25.3% for emission of >1000 nm, the highest among all LEDs with emission of >1000 nm. We further demonstrate the scalability of the approach by fabricating large-area (30 mm × 30 mm) NIR-II LEDs with uniform high performance.

Abstract:

Molecular piezoelectrics are a potentially disruptive technology, enabling a new generation of self-powered electronics that are flexible, high performing, and inherently low in toxicity. Although significant efforts have been made toward understanding their structural design by targeted manipulation of phase transition behavior, the resulting achievable piezoresponse has remained limited. In this work, we use a low-symmetry, zero-dimensional (0D) inorganic framework alongside a carefully selected ‘quasi-spherical’ organic cation to manipulate organic–inorganic interactions and thus form the hybrid, piezoelectric material [(CH3)3NCH2I]3Bi2I9. Using variable–temperature single crystal X-ray diffraction and solid-state nuclear magnetic resonance spectroscopy, we demonstrate that this material simultaneously exhibits an order–disorder and displacive symmetry-breaking phase transition. This phase transition is mediated by halogen bonding between the organic and inorganic frameworks and results in a large piezoelectric response, d 33 = 161.5 pm/V. This value represents a 4-fold improvement on previously reported halobismuthate piezoelectrics and is comparable to those of commercial inorganic piezoelectrics, thus offering a new pathway toward low-cost, low-toxicity mechanical energy harvesting and actuating devices.

Abstract:

Perovskite solar cells represent a promising technology in the photovoltaic industry due to their high power conversion efficiency, potential for cost-effective manufacturing and versatile applications. The most stable and efficient perovskites to date rely on lead (Pb), raising concerns about leaching into the environment; however Pb release so far has only been quantified under laboratory conditions, and no field-based assessment under real outdoor expsosure has yet evaluated this risk. The present study quantified Pb leaching from various metal-halide perovskite compositions, device stacks and encapsulation approaches in a rooftop installation for up to 9 months. Pb leaching was low across all tested configurations, even in intentionally damaged materials. Glass–glass encapsulated tandem devices shattered by hail and plastic-encapsulated samples damaged by 100 µm pinholes released only 0.07% ± 0.01% and 0.15% ± 0.14% of their initial Pb, respectively, likely due to the slow diffusion of Pb cations in water. The highest leaching (4.81% ± 0.02%) occurred in unlaminated laboratory devices, demonstrating the importance of proper lamination. A self-developed freeware web tool was used to calculate predicted soil concentrations and evaluate potential impacts. Even for unlaminated devices, concentrations would only slightly exceed natural background levels (5.6 mg kg−1 increase), with negligible effects on soil fertility. A hypothetical worst-case scenario assuming a 1000 nm thick perovskite layer and complete Pb leaching onto a narrow strip of soil predicted a negative impact on soil fertility; however remediation would still not be required under Swiss environmental regulations. Overall, current industry-standard encapsulation limits Pb leaching to levels that almost completely mitigate negative impacts on soil health.