Strategically Manipulated Polymer Solar Cells to Incorporate Plasmonically Enhanced Spectral Upconversion Backplane

• Published in: Advanced optical materials 2020-08, Vol.8 (16), p.n/a
• Main Authors: Cho, Ha‐Eun, Lee, Na‐Kyung, Song, Young Jin, Hong, Jinwook, Kang, Hyelim, Lim, Soo Yeong, Lee, Jaegab, Kim, Hyung Min, Lee, Nohyun, Cho, Seok Ho, Lee, Sung‐Min
• Format: Article
• Language: English
• Subjects: Backplanes; Efficiency; Energy gap; Erbium; Materials science; metal/dielectric multilayer; Multilayers; Nanoparticles; Optics; Performance degradation; Photoelectric effect; Photoelectric emission; Photon absorption; Photons; Photovoltaic cells; plasmonic nanostructures; polymer solar cells; Polymers; selectively transparent electrode; Solar cells; spectral upconversion; Upconversion; Ytterbium
• ISSN: 2195-1071; 2195-1071
• DOI: 10.1002/adom.202000466

Spectral upconversion systems placed underneath solar cells have the considerable potential for enhancement of the photovoltaic performance as they allow additional absorption for the solar photons with energy below the bandgap of active materials. However, their application to a type of ultrathin solar cells for achieving the meaningful benefit of the efficiency improvement is challenging, because a pre‐existing rear‐side reflector that substantially increases the photon absorption needs to be eliminated for photonic interaction between photovoltaic active layer and upconversion medium, and hence a level of cell efficiency becomes limited. Herein a facile strategy is presented that can circumvent the issue of performance deterioration arising from the expelled reflector for integrating plasmonically enhanced upconversion systems with ultrathin nonfullerene‐based polymer solar cells. By employing a wavelength‐selectively reflective rear electrode of metal/dielectric multilayer that enables the photon penetration only at excitation and emission wavelengths of the upconversion process, the effect of photocurrent improvement with uncompromising efficiency levels can be expected from the plasmonic upconversion backplane comprising NaYF4:Yb3+,Er3+ core‐shell nanoparticles and metallic nanostructure. Systematic studies of optical process and resulting device performance in both experiments and numerical modeling provide the optimal design scheme for high‐performance polymer solar cells assisted with upconversion systems. A strategic design of polymer solar cells that can incorporate the plasmonically enhanced upconversion backplane is presented by employing wavelength‐selectively transparent rear‐side electrodes. The selectively transparent rear electrodes can allow the photon transmission only at excitation and emission wavelengths of the upconversion process, thereby enabling additional absorption for sub‐bandgap photons without compromise of pre‐existing levels of the photovoltaic performance.