Research Progress of Layer-by-layer Deposited Organic Solar Cells

In the recent 30 years, donor and acceptor materials mixed bulk heterojunction (BHJ) are considered to be the most ideal device structure of organic photovoltaics (OPVs). The efficiency of exciton dissociation and charge transport can be improved by optimizing the donor-acceptor interpenetrating network structure in the active layer, which should be an effective way to improve the performance of BHJ OPVs. The layer-by-layer (LbL) OPVs are constructed by sequentially depositing donor and acceptor, which have been developed rapidly in recent years. The power conversion efficiency (PCE) of LbL OPVs can be comparable with that of BHJ OPVs, indicating that many scientific issues need to be further studied in OPVs. This review summarizes the representative achievements of LbL OPVs from the working mechanism, optimization strategy and large-area production potential. The key roles of additives, annealing treatment and multi-component strategy in improving device performance are emphasized. The problems existing in LbL OPVs are discussed, and the future prospects of LbL OPVs are outlooked.