Unlocking the Bottlenecks for Solution-Processed Narrow Bandgap Solar Cells with Less or No Lead – NBG_SolarCells

Solar radiation is a promising renewable energy source to combat the global energy crisis and climate change. Towards large-scale applications, photovoltaic (PV) technologies with a lower energy payback time is desirable. Nevertheless, there are persistent challenges in developing solution-processed narrow bandgap (NBG) solar cells capable of harvesting near-infrared (NIR) photons, a critical aspect limiting the development of all-solution-processed tandem PV technologies. Aside from material stability issues, a significant hurdle lies in the limited carrier diffusion length of many NIR-absorbing solution-processed PV materials, which constrains absorber thickness and photocurrent generation. "NBG_SolarCells" is dedicated to developing solution-processed NIR-absorbing solar cells by employing a combination of material and optical strategies to address the following objectives: (1) Develop narrow bandgap (Eg) solution-processed solar cells capable to harvest photons in the NIR spectrum, with reduced or lead (Pb)-free compositions; Here, two PV systems are selected based on (a) Sn-Pb perovskites and (b) AgBiS2 colloidal quantum dots (QDs); (2) Achieve fundamental understandings on the material bottlenecks of these two PV systems and to propose mitigating approaches to reduce carrier loss channels and to prevent oxidation; (3) Unlock their full potential by developing innovative light-management approaches based on nanophotonics and plasmonics to boost the solar cell performances.
Toward these objectives, a team containing three CNRS laboratories with highly complementary skills is formed. Within the 48-month tight collaborative research proposed here, by a holistic approach to improve both materials and optical properties, we aim at obtaining breakthroughs on the photovoltaic performance of the two above-mentioned solution-processed NIR-absorbing solar cell systems with less-lead and lead-free compositions by surpassing the photocurrent limits currently constrained by their short carrier diffusion lengths. By the end of the project, we endeavor to achieve a single-junction PCE > 23% and > 10% on Sn-Pb perovskite and AgBiS2 QD solar cells, respectively, with prolonged ambient stability and application outlooks for all-solution-processed tandem solar cells as the NBG subcell.