Bilby D, Frieberg B, Kramadhati S, Green P, Kim J. Design considerations for electrode buffer layer materials in polymer solar cells.
ACS Appl Mater Interfaces 2014;
6:14964-14974. [PMID:
25116039 DOI:
10.1021/am502673e]
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Abstract
Electrode buffer layers in polymer-based photovoltaic devices enable highly efficient devices. In the absence of buffer layers, we show that diode rectification is lost in ITO/P3HT:PCBM/Ag (ITO = indium tin oxide; P3HT = poly(3-hexylthiophene); PCBM = phenyl C61-butyric acid methyl ester) devices due to nonselective charge injection through the percolated phase pathways of a bulk heterojunction active layer. Charge-selective injection, and thus rectification and device function, can be regained by placing thin, polymeric buffer layers that break the direct electrode-active layer contact. Additionally, we show that strong active layer-buffer layer interactions lead to unwanted vertical phase separation and a kinked current-voltage curve. Device function is regained, increasing power conversion efficiency from 3.6% to 7.2%, by placing a noninteracting layer between the buffer and active layer. These results guide the design and selection of future polymeric electrode buffer layers for efficient polymer solar cell devices.
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