Layered All‐Polymer Solar Cells with Efficiency of 18.34% by Employing Alloyed Polymer Donors

Abstract A series of layered all‐polymer solar cells (LA‐PSCs) with the normal or inverted structure are prepared by employing a sequential spin‐coating method with PBQx‐TCl, PM1 as polymer donor, and PY‐DT as polymer acceptor. The power conversion efficiency (PCE) of normal LA‐PSCs can be improved from 17.20% to 18.34% by incorporating 30 wt.% PM1 into the PBQx‐TCl layer, resulting from simultaneously increased J SC of 25.35 mA cm −2 , V OC of 0.971 V and FF of 74.49%. The PCE improvement of inverted LA‐PSCs can also be achieved by employing PBQx‐TCl:PM1 as donor layers. The mixed PBQx‐TCl and PM1 prefer to form the alloyed states in the LA‐PSCs, which can be confirmed by the gradually increased V OC s of LA‐PSCs with more PM1 content in donor layers. Meanwhile, the photogenerated excitons in donor layers can also be dissociated at the interface between PBQx‐TCl and PM1, especially for the excitons located near the ITO electrode. The exciton dissociation between PBQx‐TCl and PM1 can provide an additional channel for improving the exciton utilization efficiency, as confirmed by the positive external quantum efficiency spectral difference (∆EQE) values for the normal and inverted LA‐PSCs with PBQx‐TCl:PM1 or PBQx‐TCl as donor layers. Over 6.6% PCE improvement of LA‐PSCs can be realized by using alloyed PBQx‐TCl:PM1 as the donor layer.