Series vs parallel connected organic tandem solar cells: Cell performance and impact on the design and operation of functional modules

Abstract

Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. b s t r a c tTandem solar cells are the best approach to maximize the light harvesting and adjust the overall absorption of the cell to the solar irradiance spectrum. Usually, the front and back subcells are connected in series in two-terminal device (2T) designs which require a current matching between both subcells in order to avoid potential losses. Alternatively, they can also be connected in parallel giving rise to a three terminal connection (3T). In principle, both designs have their assets and drawbacks in terms of device performance, design and materials' characterization. In this letter, we theoretically and experimentally confront both designs with each other (2T and 3T). Theoretical estimations show a maximum PCE of 15% for 2T and about 13% for 3T structures with ideal bandgaps for the front and back cell. However, 3T tandem devices can yield higher efficiencies than 2T for some specific material combinations whose theoretical values are between 10% and 12%. Therefore, other aspects related to the fabrication feasibility are studied in order to analyze the most convenient approach for module development. The need of a conducting interlayer restricts the width of the cell and causes a 3% reduction in the geometrical fill factor of the module in comparison to the 2T approach. The R2R processing of modules with 3T cells would also require an additional laser step. Finally, a couple of existing material combinations have been experimentally implemented into 2T and 3T t...

Performance and Matching Band Structure Analysis of Tandem Organic Solar Cells Using Machine Learning Approaches

“…Based on the aforementioned machine‐learning analysis, wide‐bandgap donor materials and low‐bandgap materials can be used for fabricating for front cells and rear cells, respectively. This finding is consistent with a recently demonstrated study that putting a wide‐bandgap bulk heterojunction over a low bandgap bulk heterojunction can reduce thermalization losses and improve the tandem OSCs efficiency . Recently, Peng and coworkers demonstrated a tandem OSC with a PCE of 14.52%.…”

High‐Efficiency Nonfullerene Organic Solar Cells with a Parallel Tandem Configuration

“…Compared to the series‐connected configuration, photocurrent matching is not strictly required for the parallel tandem structure . The photocurrent of a tandem cell is typically a simple summation of each subcell . The substantial requirement of open‐circuit voltage ( V OC ) matching in the parallel tandem can easily be resolved by using a homojunction (same bulk heterojunction (BHJ) active layer).…”

Polymer:fullerene solar cells: materials, processing issues, and cell layouts to reach power conversion efficiency over 10%, a review

“…The connection among the subcells can be performed either in series (two terminals) or in parallel (three terminals). [125][126][127] The front layer should ideally absorb only most of the light corresponding to wavelengths of its maximum absorption coefficient. On the contrary, the light that is not absorbed by the front cell, belonging to wavelengths of maximum absorption of the second layer, will be more efficiently absorbed by the polymer of the back cell.…”