Charge Transport Layers in Inverted Non‐Fullerene Organic Solar Cells: Current Challenges and Future Prospects

The non‐fullerene acceptors (NFAs)‐based organic solar cells (OSCs) with a conventional structure have reached an excellent device efficiency of 21%. However, the best efficiency of inverted OSCs, despite their better operational stability, remains limited to ∼20% only. One of the root causes stems from the charge transport materials, which greatly affect the charge extraction/collection, electrode interface recombination, vertical donor/acceptor phase separation, etc. This Perspective focuses on the charge transport layers for inverted NFA‐based OSCs, aiming to narrow the efficiency gap with conventional OSCs and even surpass it. First, we summarized recent advances in modifying typically used metal oxide electron transport layers, particularly zinc oxide (ZnO) and tin oxide (SnO 2 ). Then, the progress in alternative electron transport materials and currently used hole transport materials for the inverted structure was also highlighted. Finally, we suggested some promising research directions to guide the future development of highly efficient and stable inverted NFA‐based OSCs.