Nature study reports one‑year outdoor stability of perovskite–silicon tandem mini‑modules

A team led by Helmholtz‑Zentrum Berlin reports in Nature today that perovskite–silicon tandem mini‑modules maintained performance over a full year of outdoor operation and passed standard accelerated reliability tests. The work, conducted with Oxford PV and the US National Renewable Energy Laboratory, addresses the durability hurdle that has limited commercial deployment.

The most immediate impact is on bankability assessments. Lenders and developers rely on IEC 61215 style tests, so third‑party data that tandems can clear those protocols, and hold up in the field, is a prerequisite for project financing.

The study, led by Steve Albrecht at Helmholtz‑Zentrum Berlin, evaluated fully encapsulated tandem mini‑modules with areas near 100 square centimeters. Devices started near 26 percent efficiency, then underwent damp heat, thermal cycling, ultraviolet preconditioning, and mechanical load tests that mirror IEC procedures, followed by 12 months outdoors at sites with cold continental, temperate, and hot desert climates.

Researchers report less than five percent relative degradation after the lab sequence and after the outdoor exposure, with continuous monitoring of maximum power point and periodic flash testing by NREL. The team used polyisobutylene edge seals, low permeability glass, and an additional thin‑film barrier to limit moisture ingress, and they logged leakage currents and series resistance drift to isolate failure modes.

The paper shows tandems can survive standardized stress and a year of field conditions when packaging is robust. It does not demonstrate a 25 year lifetime, and it does not establish yield or reliability at full module scale near 2 square meters. The authors note that encapsulant selection, ion migration under reverse bias, and long term ultraviolet stability of the perovskite remain active risks.

Oxford PV co‑founder Henry Snaith, who co‑authored the work with Albrecht and collaborators at NREL, Fraunhofer ISE, and EPFL, said the outdoor data complements existing cell level stability reports. NREL reliability expert Michael Kempe, a co‑author, emphasized that consistent pass or fail criteria aligned to IEC test sequences will be needed before independent engineering firms can issue bankability opinions.

For manufacturers, the results support pilot deployments and utility‑scale demonstrations in 2027 contract cycles, potentially with performance guarantees tied to encapsulation stack choices. The findings raise the bar for competing silicon TOPCon and heterojunction lines, and they put focus on glass, barrier films, and laser interconnect tooling as near term supply chain pinch points.