Unique Hole Transport Layer of PCDTBT Doped with PCPDTBT for Perovskite Solar Cells

Abstract

Perovskite solar cells are a major revolution in the field of photovoltaics. The reported power conversion efficiency of perovskite solar cells was only 3.8% in the year 2009. The highest efficiency to date is 22.1%. One of the factors limiting the efficiency of perovskite solar cells is the performance of the hole transport material which extracts charges from the active layer. In order to get ohmic contact between the perovskite material (methyl ammonium lead iodide) and the anode, hole transport layers such as Spiro-OMETAD (N2,N2,N2′,N2′,N7,N7,N7′,N7′-octakis (4-methoxyphenyl) -9,9′-spirobi[9H-fluorene]-2,2′,7,7′-tetramine) and P3HT(Poly (3-hexyl thiopene -2,5 diyl)) are used. In this article, we discuss about using pristine PCDTBT ([Poly[N-9'-heptadecanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] and PCDTBT doped with PCPDTBT([Poly(4,4-bis(2-ethylhexyl)-cyclopenta-[2,1-b;3,4-b]dithiopene)- 2,6 – diyl - alt-2,1,3-benzothiadiazole-4,7-diyl]) as hole transport layers. A highest efficiency of 5.1% is attained when PCDTBT is doped with 10% PCPDTBT. Characterization techniques such as External quantum efficiency measurement, UV visible absorbance, photoluminescence and field emission electron microscopy confirm the results.