Journal Article Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. organic solar cells Inverted organic solar cell efficient light absorption electron transport layer fullerene fullerenes fulleroids interfaces interfacial modification metal oxides micro-cavity effect non-fullerene acceptors organic photovoltaics parallel tandem solar cells recombination self-assembled monolayers semitransparent electrode transient photovoltage two-dimensional p-type polymers