Development of bifacial inverted polymer solar cells using a conductivity-controlled transparent PEDOT:PSS and a striped Au electrode on the hole collection side

Abstract

An inverted bifacial polymer solar cell was developed using a conductivity-controlled transparent PEDOT:PSS as a hole collection layer and a striped Au electrode with a large open aperture ratio (Rap) as a hole collection electrode. We investigated the performance of the device by varying the inter-electrode distance of the striped Au electrode and the sheet resistance of the PEDOT:PSS film.The device using Clevios P (PEDOT:PSS) showed a maximum electric output (P w ) in the R ap range of 50 to 65 %. When alcohol-treated Clevios P (Clevios P+) with a lower electrical resistance was used, the maximum P w increased by 40 % compared with that of the device using Clevios P. The maximum P w was obtained in the R ap range of 84 % as the hole collection efficiency of the striped Au electrode improved with the decreased sheet resistance of the PEDOT:PSS.

Factors Affecting the Performance of Bifacial Inverted Polymer Solar Cells with a Thick Photoactive Layer

“…When the bifacial inverted polymer solar cell with a 200 nm thick PCBM:P3HT layer was irradiated from the ITO side, it showed a short-circuit photocurrent ( I sc ) of 7.75 mA, open-circuit voltage ( V oc ) of 0.55 V, FF of 0.54, and maximum electric output ( P w ) of 2.29 mW. In contrast, a monofacial inverted polymer solar cell using an Au plate electrode showed I sc = 7.67 mA, V oc = 0.57 V, FF = 0.61, and P w = 2.67 mW . That is, when irradiated from the front ITO electrode, the bifacial cell containing PEDOT:PSS (Clevios P) with a sheet resistance of (1.5 ± 0.5) × 10 5 Ω sq – 1 showed a slightly lower P w compared with that of the monofacial cell.…”

“…That is, when irradiated from the front ITO electrode, the bifacial cell containing PEDOT:PSS (Clevios P) with a sheet resistance of (1.5 ± 0.5) × 10 5 Ω sq – 1 showed a slightly lower P w compared with that of the monofacial cell. Thus, the PEDOT:PSS acted as a hole collection layer because the photoproduced holes were efficiently collected even by the striped Au electrodes . This implies that the built-in potential formed in the thickness direction of the PCBM:P3HT layer originates from the difference of Fermi levels of ZnO and PEDOT:PSS sandwiching the BHJ layer.…”

“…Bifacial inverted polymer solar cells with the structure ITO/ ZnO/PCBM:P3HT/PEDOT:PSS/Au containing a PCBM:P3HT layer with a thickness of 150 to 500 nm were fabricated in air by the method we described previously. 29 The glass-ITO electrodes (sheet resistance: 10 Ω sq −1 ) were cleaned by sonication in 2-propanol, washed in boiling 2-propanol, and then dried in air. The fabrication was carried out in air, controlling the relative humidity to less than 35%.…”

“…High conductivity PEDOT:PSS film, , Ag nanowire, − graphene, and metal-grid electrodes − have been applied to novel window electrodes. We recently reported the bifacial polymer solar cells using striped Au electrode …”

“…We recently reported the bifacial polymer solar cells using striped Au electrode. 29 In this work, we obtain the profile of an electric field across a photoactive layer using bifacial inverted polymer solar cells with a thick (∼500 nm) photoactive BHJ layer composed of P3HT as a donor and PCBM as an acceptor. The thick active layers have some problems such as transfer-limit of electron and hole due to the charge carrier mobility, concentration distribution of donor and acceptor, electric field distribution across the layer, and degree of microphase separation.…”