Inverted polymer solar cells integrated with small molecular electron collection layer.

Highlights: [•] An efficient inverted polymer solar cell is demonstrated. [•] The electron collection layer consists of a small molecular layer of Cs2CO3:Alq3. [•] Efficient electron extraction is achieved due to favorable energy level alignment. [•] The Cs2CO3:Alq3 layer can act as an optical spacer to modulate the incident light. [ABSTRACT FROM AUTHOR]