Inverted Organic Photovoltaics with Wide Bandgap Donors: Outperforming Noninverted Structures for Indoor Application

With their low-cost, flexibility, and lightweight nature, organic photovoltaics (OPVs) could serve as a better substitute to the conventional silicon-based solar cells. This research aims at improving OPV performance with emphasis on indoor environment where light intensity is reduced and spectral properties vary from 1-sun condition. Noninverted OPVs based on poly(3,4-ethylenedioxythiophene) polystyrenesulfonate as a hole transport layer (HTL), have been studied before but suffer from HTL stability and energy level alignment issues with respect to donor. In contrast, inverted OPVs use electron transport layers (ETLs) like zinc oxide (ZnO). They offer better stability and energy alignment. We compare inverted and noninverted OPV structures based on the wide bandgap donor material PBDB-T and the fullerene acceptor PC70BM under indoor light. With Al-doped ZnO ETLs, the inverted OPVs show better performance, reaching a maximum efficiency of 16.40%. This improvement comes from better charge extraction efficiency and less recombination loss due to accurate energy level alignment. Our findings highlight the potential of inverted OPV designs to maximize power conversion efficiency indoors. This makes them a good fit for next-generation sustainable energy solutions. Further refinement of inverted OPV designs may help advance indoor photovoltaic technologies for practical use.