Realizing High Performance Inverted Organic Solar Cells via a Nonconjugated Electrolyte Cathode Interlayer

Organic electrolyte interlayer has been widely used in organic solar cells (OSCs). However, previous reports mainly focused on conventional OSCs despite with poor stability. In more stable inverted OSCs, the application of organic electrolyte interlayer is rarely reported and the device efficiency is low. Here, a simple nonconjugated small molecule electrolyte (SME), ethylene diamine tetraacetic acid tetrasodium (EDTA-4Na), is successfully introduced into inverted OSCs as a cathode interlayer, leading to a high efficiency of 9.69%. Besides efficiency, the device stability is also improved and almost 85% of the efficiency can be maintained even after storage of 46 days. More importantly, EDTA-4Na tremendously alleviates the hysteresis phenomenon happening in organic optoelectronic devices based on ionized interlayer. As a result, stabilized power output of similar to 9.5% is obtained in OSCs with EDTA-4Na. These inspiring results prove that electrolytes with simple structure can also achieve excellent performance and that nonconjugated SME is also a competitive candidate as cathode interlayer, especially in inverted OSCs.