Microlens array induced light absorption enhancement in polymer solar cells

Abstract

Over the last decade, polymer solar cells (PSCs) have attracted a lot of attention and highest power conversion efficiencies (PCE) are now close to 10%. Here we employ an optical structure - the microlens array (MLA) - to increase light absorption inside the active layer, and PCE of PSCs increased even for optimized devices. Normal incident light rays are refracted at the MLA and travel longer optical paths inside the active layers. Two PSC systems - poly(3-hexylthiophene-2,5-diyl):(6,6)-phenyl C61 butyric acid methyl ester (P3HT:PCBM) and poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]:(6,6)-phenyl C71 butyric acid methyl ester (PCDTBT:PC70BM) - were investigated. In the P3HT:PCBM system, MLA increased the absorption, absolute external quantum efficiency, and the PCE of an optimized device by ∼4.3%. In the PCDTBT:PC70BM system, MLA increased the absorption, absolute external quantum efficiency, and PCE by more than 10%. In addition, simulations incorporating optical parameters of all structural layers were performed and they support the enhancement of absorption in the active layer with the assistance of MLA. Our results show that utilizing MLA is an effective strategy to further increase light absorption in PSCs, in which optical losses account for ∼40% of total losses. MLA also does not pose materials processing challenges to the active layers since it is on the other side of the transparent substrate.

From Nanodroplets by the Ouzo Effect to Interfacial Nanolenses

“…1,2 Nanostructures with lens shapes such as micro and nano-lenses provide a unique way to tailor surface optical properties, enabling suitability of the substrate to potential applications in the areas of bioimaging, solar cells, optical nano-sensing, surface antireflective coatings, and optical lithography. [3][4][5][6] In particular, nanolenses are able to overcome the diffraction limit in optical imaging and achieve high resolutions at low light intensities using the nearfield imaging technique. 5,7,8 Individual submicrometer lenses with different sizes and morphologies have been prepared by several methods including chemical growth, 5 chemical reflow, 9 and polymer bread.…”

Strain tunable optics of elastomeric microlens array

“…Optical microlens arrays (MLAs) have been playing important roles in many fields, such as photolithography [1], optical communication [2], organic light emitting diodes (OLEDs) [3], thin film organic photovoltaic cells [4,5], and biomimetic artificial compound eye cameras [6,7]. Some recent advancement in photonics and optoelectronics [8][9][10][11][12][13][14] requires tunability of the optics of MLAs, and therefore, a lot of research has been invested to realize tunable MLAs.…”

Organic Solar Cells: Degradation Processes and Approaches to Enhance Performance

“…The diffracted light has a longer path length in the active layer and most of it undergoes total internal reflection at the ITO anode leading to trapping of light in the active layer. Use of microlens on the incident side has been shown to improve the PCE of OSCs [41,59]. Fig.…”

“…These approaches include using textured substrates [42], gold and silver nanoparticles in the hole transport layer (HTL) and/or active layer [55][56][57][58] and microlens on the light incident side of OSCs [41,59] as shown in Fig. 10.…”