In-situ self-organized anode interlayer enables organic solar cells with simultaneously simplified processing and greatly improved efficiency to 17.8%

Highly efficient organic solar cells (OSCs) are often obtained with a multilayer structure, in which active layer is sandwiched between anode and cathode interlayer. Here we present a simple strategy to simultaneously obtain anode interlayer and boost performances of OSCs by directly adding a tiny small molecule [2-(9H-carbazol-9-yl)ethyl] phosphonic acid (2PACz) into the active layer. It is found that 2PACz with high surface energy prefers to self-organize at the bottom of PM6:Y6-BO bulk heterojunction (BHJ) blend and in-situ form anode interlayer during the film formation. Encouragingly, green solvent o-xylene processed OSCs with substantial improvement of photovoltaic performances are observed in self-organized 2PACz device with best power conversion efficiency (PCE) reaching 17.8%, notably higher than that of control device based on independently spin-coated 2PACz with a PCE of 16.8%. In-depth studies indicate the in-situ self-organized 2PACz underneath BHJ is beneficial to enhance build-in potential, suppress surface trap-assisted recombination, and induce ordered molecule stacking. Moreover, this self-organization method is implanted in a large-area OSC with 1 cm2 device area and an outstanding PCE of 15.8% is achieved. These results above highlight the great potential of in-situ self-organization method in simplifying device processing as well as improving efficiency, which make it an ideal strategy for large-area OSCs manufacture.