An Electrode Design Rule for Organic Photovoltaics Elucidated Using a Low Surface Area Electrode

Abstract

It is widely considered that charge carrier extraction in bulk‐heterojunction organic photovoltaics (BHJ OPVs) is most efficient when the area of contact between the semiconductor layers and the electrodes is maximized and the electrodes are electrically homogeneous. Herein, it is shown that ≈99% of the electrode surface can in fact be insulating without degrading the efficiency of charge carrier extraction, provided the spacing of the conducting areas is less than or equal to twice the optimal thickness of the BHJ layer. This striking result is demonstrated for BHJ OPVs with both conventional and inverted device architectures using two different types of BHJ OPVs, namely, PCDTBT:PC70BM and the ternary blend PBDB‐T:ITIC‐m:PC70BM. This finding opens the door to the use of a large pallet of materials for optical spacers and charge transport layers, based on a low density of conducting particles embedded in a wide bandgap insulating matrix.

Inverted organic photovoltaics with a solution-processed ZnO/MgO electron transport bilayer

“…The question arises as to whether the relatively limited extent of the electrode's area that is effective for charge extraction might reduce the overall device performance. Interestingly, and as shown by Dabera et al 47 , it is possible for ∼ 99% of the surface of an ETL to be electrically insulating without eroding the efficiency of charge carrier extraction given that sufficient pathways for conduction remain. Our ultrathin and non-uniform MgO interlayer appears to provide a general suppression of the leakage current (e.g.…”

Recent Progress of Organic Solar Cells with Insulating Polymers

“…Recently, Hatton and coworkers inserted the gold nanoparticle (AuNPs)‐embedded PMMA layer at the interface of ITO/MoO 3 and reported a positive effect of low‐density embedding on OSCs ( Figure ). [ 69 ] The carrier dynamics were obtained from time‐resolved PL. AuNPs accelerated the decay of PL and thus induced effective excitons in the corresponding film.…”