Acceptor Engineered Hole‐Transporting Materials for Inverted Perovskite Solar Cells

Hole‐transporting materials (HTMs) with appropriate energy‐level alignment and defect‐passivation capabilities play a key role in achieving highly efficient and stable perovskite solar cells (PSCs). In this study, two dopant‐free dipolar HTMs, BA and RDN , incorporating barbituric acid and thioxothiazolidin acceptors, respectively, were developed to examine the influence of acceptor engineering on PSC performance. Although both HTMs share the same donor framework, the differing acceptor units provide distinct interfacial properties and charge‐carrier dynamics. The barbituric acid acceptor in BA enables stronger defect passivation due to its carbonyl and ─NH groups‐rich structure, which suppresses nonradiative recombination while maintaining favorable energy‐level alignment and efficient hole transport. As a result, PSCs utilizing BA achieve a higher power conversion efficiency of 19.94% with a short‐circuit current density of 23.09 mA cm −2 , surpassing the performance of RDN ‐based devices (18.75%). These results illustrate the importance of acceptor selection toward modulating interfacial energetics along with defect passivation and highlight barbituric acid as a promising acceptor candidate for the design of high‐performance dopant‐free HTMs for PSCs.