Performance enhancement in organic solar cells and photodetectors enabled by donor phase optimization at the surface of hole transport layer

Abstract

The domain purity, material crystallinity and distribution at the interface between the active layer and the transport layer have an important impact on the performance of organic solar cells (OSCs) and organic photodetectors (OPDs), while this focal issue has received less attention in previous studies. From this perspective, a new method to simultaneously enhance the performance of OSC and OPD is proposed, namely, using a sequential deposition method to first construct a compact stacking structure of dual-donor (D18-Cl:PTO2) eutectic in the donor layer, and then induce the ordered deposition of the acceptor (Y6). Compared with the conventional bulk heterojunction (BHJ), the active layer realized by this method not only improves the crystallinity and stacking order of the constituent material on the surface of the transport layer, but also regulates a good vertical distribution, which is conducive to improving the charge transport and extraction efficiency, reducing the leakage current, and enhancing the stability of the device. As a result, the OSC device based on the D18-Cl:PTO2/Y6 structure achieves a power conversion efficiency of up to 17.65% and good light-degradation stability, which is much better than that of BHJ-based OSC (PCE of 16.37%). For the OPD, the dark current at reverse bias is reduced by more than an order of magnitude, and the maximum responsivity is improved to 0.52 A/W through the optimization of the donor phase at the interface. Moreover, the strategy does not require additional post-processing compared to the BHJ preparation, which reduces the device construction cost and process complexity, providing an effective way for developing high-performance organic optoelectronic devices.