Over 19.8% efficiency layer-by-layer organic photovoltaics by incorporating a high-mobility crystallinity material into the acceptor layer

Abstract

A series of layer-by-layer organic photovoltaics (LOPVs) were constructed using D18 as the donor and L8-BO, featuring exciton self-dissociation characteristics, as acceptor. A trace amount of high crystallinity, high-hole-mobility polymer P66 was intentionally introduced into the L8-BO layer to enhance the hole transport. The power conversion efficiency (PCE) of the LOPVs improved from 18.97% to 19.81% upon the addition of 0.005 wt.% P66 to the L8-BO layer, originating from the concurrent increases in short-circuit current density from 26.87 to 27.72 mA/cm² and fill factor from 78.61% to 79.39%. The introduction of P66 into the L8-BO layer forms an efficient hole-transport network, promoting the transport of holes generated by exciton self-dissociation in L8-BO. In addition, introducing P66 optimizes molecular packing, thereby enhancing charge extraction and transport within active layers. The universality of incorporating P66 into acceptor layers is further demonstrated in a series of LOPVs with different acceptors. This work indicates that introducing materials with high hole mobility and crystallinity into the acceptor layer is a promising strategy for boosting the performance of LOPVs.

Graphical abstract

Keywords

organic photovoltaics / hole transport / high crystallinity / layer by layer

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