Locking-In Optimal Nanoscale Structure Induced by Naphthalenediimide-Based Polymeric Additive Enables Efficient and Stable Inverted Polymer Solar Cells

Operational stability and high performance are the most critical issues that must be addressed in order to propel and advance the current polymer solar cell (PSC) technology to the next level, such as manufacturing and mass production. Herein, we report a high power conversion efficiency (PCE) of 11.2%, together with an excellent device stability in PTB7-Th:PC71BM-based PSCs in the inverted structure by introducing the n-type P(NDI2OD-T2) macromolecular additive (>75% PCE retention at high temperature up to 120 degrees C, >97% PCE retention after 6 months in inert conditions, >93% PCE retention after 2 months in air with encapsulation, and >80% PCE retention after 140 h in air without encapsulation). The PCE is the highest value ever reported in the single-junction systems based on the PTB7 family and is also comparable to the previously reported highest PCE of inverted PSCs. These promising results are attributed to the efficient optimization and stabilization of the blend film morphology in the photoactive layer, achieved using the P(NDI2OD-T2) additive. From the perspective of manufacturing, our studies demonstrate a promising pathway for fabricating low-cost PSCs with high efficiency as well as long-term stability.