Organic–inorganic hybrid perovskites provide not only an exceptionally rich area of research but also remarkable power conversion efficiency relevant to commercial use. However, developing efficient organic hole transport layers remains challenging, due partly to the subtle electronic behavior of perovskite and complications introduced by the use of reactive dopants. Here we show, through time-resolved microwave conductivity, the quantification of a hole transfer process from methylammonium lead triiodide perovskite to eight kinds of conjugated polymers with and without a Li dopant. The time evolution of hole transfer yield is characterized by kinetic parameters, which are further examined in conjunction with solar cell performance, energetics, and temporal profiles triggered by exposure to air at the minute scale. Using statistics and LASSO (least absolute shrinkage and selection operator) analysis, we identify an accurate descriptor that correlates with device output. This work explores the design of or...